/*-------------------------------------------------------------------------
 *
 * dependency.c
 *	  Functions to reason about distributed objects and their dependencies
 *
 * Copyright (c) Citus Data, Inc.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "miscadmin.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/skey.h"
#include "access/sysattr.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid_d.h"
#include "catalog/pg_class.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_depend.h"
#include "catalog/pg_extension_d.h"
#include "catalog/pg_foreign_data_wrapper_d.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_proc_d.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_rewrite_d.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_type.h"
#include "commands/extension.h"
#include "common/hashfn.h"
#include "utils/fmgroids.h"
#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"

#include "pg_version_constants.h"

#include "distributed/citus_depended_object.h"
#include "distributed/commands.h"
#include "distributed/commands/utility_hook.h"
#include "distributed/hash_helpers.h"
#include "distributed/listutils.h"
#include "distributed/metadata/dependency.h"
#include "distributed/metadata/distobject.h"
#include "distributed/metadata_cache.h"
#include "distributed/metadata_sync.h"
#include "distributed/version_compat.h"

/*
 * ObjectAddressCollector keeps track of collected ObjectAddresses. This can be used
 * together with RecurseObjectDependencies.
 *
 * We keep three different datastructures for the following reasons
 *  - A List ordered by insert/collect order
 *  - A Set to quickly O(1) check if an ObjectAddress has already been collected
 *  - A set to check which objects are already visited
 */
typedef struct ObjectAddressCollector
{
	List *dependencyList;
	HTAB *dependencySet;

	HTAB *visitedObjects;
} ObjectAddressCollector;

/*
 * DependencyMode distinguishes the data stored in DependencyDefinition. For details see
 * DependencyDefinition's inline comments in the data union.
 */
typedef enum DependencyMode
{
	DependencyObjectAddress,
	DependencyPgDepend,
	DependencyPgShDepend
} DependencyMode;

typedef struct DependencyDefinition
{
	/* describe how the dependency data is stored in the data field */
	DependencyMode mode;

	/*
	 * Dependencies can be found in different ways and therefore stored differently on the
	 * definition.
	 */
	union
	{
		/*
		 * pg_depend is used for dependencies found in the database local pg_depend table.
		 * The entry is copied while scanning the table. The record can be inspected
		 * during the chasing algorithm to follow dependencies of different classes, or
		 * based on dependency type.
		 */
		FormData_pg_depend pg_depend;

		/*
		 * pg_shdepend is used for dependencies found in the global pg_shdepend table.
		 * The entry is copied while scanning the table. The record can be inspected
		 * during the chasing algorithm to follow dependencies of different classes, or
		 * based on dependency type.
		 */
		FormData_pg_shdepend pg_shdepend;

		/*
		 * address is used for dependencies that are artificially added during the
		 * chasing. Since they are added by citus code we assume the dependency needs to
		 * be chased anyway, of course it will only actually be chased if the object is a
		 * supported object by citus
		 */
		ObjectAddress address;
	} data;
} DependencyDefinition;

/*
 * ViewDependencyNode represents a view (or possibly a table) in a dependency graph of
 * views.
 */
typedef struct ViewDependencyNode
{
	Oid id;
	int remainingDependencyCount;
	List *dependingNodes;
}ViewDependencyNode;


static List * GetRelationSequenceDependencyList(Oid relationId);
static List * GetRelationFunctionDependencyList(Oid relationId);
static List * GetRelationTriggerFunctionDependencyList(Oid relationId);
static List * GetPublicationRelationsDependencyList(Oid relationId);
static List * GetRelationStatsSchemaDependencyList(Oid relationId);
static List * GetRelationIndicesDependencyList(Oid relationId);
static DependencyDefinition * CreateObjectAddressDependencyDef(Oid classId, Oid objectId);
static List * GetTypeConstraintDependencyDefinition(Oid typeId);
static List * CreateObjectAddressDependencyDefList(Oid classId, List *objectIdList);
static ObjectAddress DependencyDefinitionObjectAddress(DependencyDefinition *definition);
static DeferredErrorMessage * DeferErrorIfHasUnsupportedDependency(const ObjectAddress *
																   objectAddress);

/* forward declarations for functions to interact with the ObjectAddressCollector */
static void InitObjectAddressCollector(ObjectAddressCollector *collector);
static void CollectObjectAddress(ObjectAddressCollector *collector,
								 const ObjectAddress *address);
static bool IsObjectAddressCollected(ObjectAddress findAddress,
									 ObjectAddressCollector *collector);
static ObjectAddress * GetUndistributableDependency(const ObjectAddress *objectAddress);
static bool ObjectAddressHasExtensionDependency(const ObjectAddress *target,
												ObjectAddress *extensionAddress,
												int extensionDependency);
static void MarkObjectVisited(ObjectAddressCollector *collector,
							  ObjectAddress target);
static bool TargetObjectVisited(ObjectAddressCollector *collector,
								ObjectAddress target);

typedef List *(*expandFn)(ObjectAddressCollector *collector, ObjectAddress target);
typedef bool (*followFn)(ObjectAddressCollector *collector,
						 DependencyDefinition *definition);
typedef void (*applyFn)(ObjectAddressCollector *collector,
						DependencyDefinition *definition);

/* forward declaration of functions that recurse pg_depend */
static void RecurseObjectDependencies(ObjectAddress target, expandFn expand,
									  followFn follow, applyFn apply,
									  ObjectAddressCollector *collector);
static List * DependencyDefinitionFromPgDepend(ObjectAddress target);
static List * DependencyDefinitionFromPgShDepend(ObjectAddress target);
static bool FollowAllSupportedDependencies(ObjectAddressCollector *collector,
										   DependencyDefinition *definition);
static bool FollowNewSupportedDependencies(ObjectAddressCollector *collector,
										   DependencyDefinition *definition);
static bool FollowAllDependencies(ObjectAddressCollector *collector,
								  DependencyDefinition *definition);
static bool FollowExtAndInternalDependencies(ObjectAddressCollector *collector,
											 DependencyDefinition *definition);
static void ApplyAddToDependencyList(ObjectAddressCollector *collector,
									 DependencyDefinition *definition);
static void ApplyAddCitusDependedObjectsToDependencyList(
	ObjectAddressCollector *collector,
	DependencyDefinition *definition);
static List * GetViewRuleReferenceDependencyList(Oid relationId);
static List * ExpandCitusSupportedTypes(ObjectAddressCollector *collector,
										ObjectAddress target);
static List * ExpandForPgVanilla(ObjectAddressCollector *collector,
								 ObjectAddress target);
static List * GetDependentRoleIdsFDW(Oid FDWOid);
static List * ExpandRolesToGroups(Oid roleid);
static ViewDependencyNode * BuildViewDependencyGraph(Oid relationId, HTAB *nodeMap);
static bool IsObjectAddressOwnedByExtension(const ObjectAddress *target,
											ObjectAddress *extensionAddress);
static bool ErrorOrWarnIfObjectHasUnsupportedDependency(const
														ObjectAddress *objectAddress);

/*
 * GetUniqueDependenciesList takes a list of object addresses and returns a new list
 * of ObjectAddesses whose elements are unique.
 */
List *
GetUniqueDependenciesList(List *objectAddressesList)
{
	ObjectAddressCollector objectAddressCollector = { 0 };
	InitObjectAddressCollector(&objectAddressCollector);

	ObjectAddress *objectAddress = NULL;
	foreach_declared_ptr(objectAddress, objectAddressesList)
	{
		if (IsObjectAddressCollected(*objectAddress, &objectAddressCollector))
		{
			/* skip objects that are already collected */
			continue;
		}

		CollectObjectAddress(&objectAddressCollector, objectAddress);
	}

	return objectAddressCollector.dependencyList;
}


/*
 * GetDependenciesForObject returns a list of ObjectAddesses to be created in order
 * before the target object could safely be created on a worker. Some of the object might
 * already be created on a worker. It should be created in an idempotent way.
 */
List *
GetDependenciesForObject(const ObjectAddress *target)
{
	ObjectAddressCollector collector = { 0 };
	InitObjectAddressCollector(&collector);

	RecurseObjectDependencies(*target,
							  &ExpandCitusSupportedTypes,
							  &FollowNewSupportedDependencies,
							  &ApplyAddToDependencyList,
							  &collector);

	return collector.dependencyList;
}


/*
 * GetAllSupportedDependenciesForObject returns a list of all the ObjectAddresses to be
 * created in order before the target object could safely be created on a worker, if all
 * dependent objects are distributable. As a caller, you probably need to use
 * GetDependenciesForObject() which eliminates already distributed objects from the returned
 * list.
 *
 * Some of the object might already be created on a worker. It should be created
 * in an idempotent way.
 */
List *
GetAllSupportedDependenciesForObject(const ObjectAddress *target)
{
	ObjectAddressCollector collector = { 0 };
	InitObjectAddressCollector(&collector);

	RecurseObjectDependencies(*target,
							  &ExpandCitusSupportedTypes,
							  &FollowAllSupportedDependencies,
							  &ApplyAddToDependencyList,
							  &collector);

	return collector.dependencyList;
}


/*
 * GetAllDependenciesForObject returns a list of all the dependent objects of the given
 * object irrespective of whether the dependent object is supported by Citus or not, if
 * the object can be found as dependency with RecurseObjectDependencies and
 * ExpandCitusSupportedTypes.
 *
 * This function will be used to provide meaningful error messages if any dependent
 * object for a given object is not supported. If you want to create dependencies for
 * an object, you probably need to use GetDependenciesForObject().
 */
List *
GetAllDependenciesForObject(const ObjectAddress *target)
{
	ObjectAddressCollector collector = { 0 };
	InitObjectAddressCollector(&collector);

	RecurseObjectDependencies(*target,
							  &ExpandCitusSupportedTypes,
							  &FollowAllDependencies,
							  &ApplyAddToDependencyList,
							  &collector);

	return collector.dependencyList;
}


/*
 * GetAllCitusDependedDependenciesForObject returns all the dependencies
 * which are owned by citus extension for the target.
 */
List *
GetAllCitusDependedDependenciesForObject(const ObjectAddress *target)
{
	ObjectAddressCollector collector = { 0 };
	InitObjectAddressCollector(&collector);

	RecurseObjectDependencies(*target,
							  &ExpandForPgVanilla,
							  &FollowExtAndInternalDependencies,
							  &ApplyAddCitusDependedObjectsToDependencyList,
							  &collector);

	return collector.dependencyList;
}


/*
 * OrderObjectAddressListInDependencyOrder given a list of ObjectAddresses return a new
 * list of the same ObjectAddresses ordered on dependency order where dependencies
 * precedes the corresponding object in the list.
 *
 * The algortihm traveses pg_depend in a depth first order starting at the first object in
 * the provided list. By traversing depth first it will put the first dependency at the
 * head of the list with dependencies depending on them later.
 *
 * If the object is already in the list it is skipped for traversal. This happens when an
 * object was already added to the target list before it occurred in the input list.
 */
List *
OrderObjectAddressListInDependencyOrder(List *objectAddressList)
{
	ObjectAddressCollector collector = { 0 };
	InitObjectAddressCollector(&collector);

	ObjectAddress *objectAddress = NULL;
	foreach_declared_ptr(objectAddress, objectAddressList)
	{
		if (IsObjectAddressCollected(*objectAddress, &collector))
		{
			/* skip objects that are already ordered */
			continue;
		}

		RecurseObjectDependencies(*objectAddress,
								  &ExpandCitusSupportedTypes,
								  &FollowAllSupportedDependencies,
								  &ApplyAddToDependencyList,
								  &collector);

		CollectObjectAddress(&collector, objectAddress);
	}

	return collector.dependencyList;
}


/*
 * RecurseObjectDependencies recursively visits all dependencies of an object. It sources
 * the dependencies from pg_depend and pg_shdepend while 'expanding' the list via an
 * optional `expand` function.
 *
 * Starting from the target ObjectAddress. For every dependency found the `follow`
 * function will be called. When `follow` returns true it will recursively visit the
 * dependencies for that object.
 *
 * Visiting will happen in depth first order, which is useful to create or sorted lists of
 * dependencies to create.
 *
 * For all dependencies that should be visited the apply function will be called. This
 * function is designed to be the mutating function for the context being passed. Although
 * nothing prevents the follow function to also mutate the context.
 *
 *  - follow will be called on the way down, so the invocation order is top to bottom of
 *    the dependency tree
 *  - apply is called on the way back, so the invocation order is bottom to top. Apply is
 *    not called for entries for which follow has returned false.
 */
static void
RecurseObjectDependencies(ObjectAddress target, expandFn expand, followFn follow,
						  applyFn apply, ObjectAddressCollector *collector)
{
	if (TargetObjectVisited(collector, target))
	{
		/* prevent infinite loops due to circular dependencies */
		return;
	}

	MarkObjectVisited(collector, target);

	/* lookup both pg_depend and pg_shdepend for dependencies */
	List *pgDependDefinitions = DependencyDefinitionFromPgDepend(target);
	List *pgShDependDefinitions = DependencyDefinitionFromPgShDepend(target);
	List *dependenyDefinitionList = list_concat(pgDependDefinitions,
												pgShDependDefinitions);

	/* concat expanded entries if applicable */
	if (expand != NULL)
	{
		List *expandedEntries = expand(collector, target);
		dependenyDefinitionList = list_concat(dependenyDefinitionList, expandedEntries);
	}

	/* iterate all entries and recurse depth first */
	DependencyDefinition *dependencyDefinition = NULL;
	foreach_declared_ptr(dependencyDefinition, dependenyDefinitionList)
	{
		if (follow == NULL || !follow(collector, dependencyDefinition))
		{
			/* skip all pg_depend entries the user didn't want to follow */
			continue;
		}

		/*
		 * recurse depth first, this makes sure we call apply for the deepest dependency
		 * first.
		 */
		ObjectAddress address = DependencyDefinitionObjectAddress(dependencyDefinition);
		RecurseObjectDependencies(address, expand, follow, apply, collector);

		/* now apply changes for current entry */
		if (apply != NULL)
		{
			apply(collector, dependencyDefinition);
		}
	}
}


/*
 * DependencyDefinitionFromPgDepend loads all pg_depend records describing the
 * dependencies of target.
 */
static List *
DependencyDefinitionFromPgDepend(ObjectAddress target)
{
	ScanKeyData key[2];
	HeapTuple depTup = NULL;
	List *dependenyDefinitionList = NIL;

	/*
	 * iterate the actual pg_depend catalog
	 */
	Relation depRel = table_open(DependRelationId, AccessShareLock);

	/* scan pg_depend for classid = $1 AND objid = $2 using pg_depend_depender_index */
	ScanKeyInit(&key[0], Anum_pg_depend_classid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target.classId));
	ScanKeyInit(&key[1], Anum_pg_depend_objid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target.objectId));
	SysScanDesc depScan = systable_beginscan(depRel, DependDependerIndexId, true, NULL, 2,
											 key);

	while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
	{
		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
		DependencyDefinition *dependency = palloc0(sizeof(DependencyDefinition));

		/* keep track of all pg_depend records as dependency definitions */
		dependency->mode = DependencyPgDepend;
		dependency->data.pg_depend = *pg_depend;
		dependenyDefinitionList = lappend(dependenyDefinitionList, dependency);
	}

	systable_endscan(depScan);
	relation_close(depRel, AccessShareLock);

	return dependenyDefinitionList;
}


/*
 * DependencyDefinitionFromPgShDepend loads all pg_shdepend records describing the
 * dependencies of target.
 */
static List *
DependencyDefinitionFromPgShDepend(ObjectAddress target)
{
	ScanKeyData key[3];
	HeapTuple depTup = NULL;
	List *dependenyDefinitionList = NIL;

	/*
	 * iterate the actual pg_shdepend catalog
	 */
	Relation shdepRel = table_open(SharedDependRelationId, AccessShareLock);

	/*
	 * Scan pg_shdepend for dbid = $1 AND classid = $2 AND objid = $3 using
	 * pg_shdepend_depender_index
	 *
	 * where $1 is decided as follows:
	 *   - shared dependencies $1 = InvalidOid
	 *   - other dependencies $1 = MyDatabaseId
	 * This is consistent with postgres' static classIdGetDbId function
	 */
	Oid dbid = InvalidOid;
	if (!IsSharedRelation(target.classId))
	{
		dbid = MyDatabaseId;
	}
	ScanKeyInit(&key[0], Anum_pg_shdepend_dbid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(dbid));
	ScanKeyInit(&key[1], Anum_pg_shdepend_classid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target.classId));
	ScanKeyInit(&key[2], Anum_pg_shdepend_objid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target.objectId));
	SysScanDesc shdepScan = systable_beginscan(shdepRel, SharedDependDependerIndexId,
											   true, NULL, 3, key);

	while (HeapTupleIsValid(depTup = systable_getnext(shdepScan)))
	{
		Form_pg_shdepend pg_shdepend = (Form_pg_shdepend) GETSTRUCT(depTup);
		DependencyDefinition *dependency = palloc0(sizeof(DependencyDefinition));

		/* keep track of all pg_shdepend records as dependency definitions */
		dependency->mode = DependencyPgShDepend;
		dependency->data.pg_shdepend = *pg_shdepend;
		dependenyDefinitionList = lappend(dependenyDefinitionList, dependency);
	}

	systable_endscan(shdepScan);
	relation_close(shdepRel, AccessShareLock);

	return dependenyDefinitionList;
}


/*
 * InitObjectAddressCollector takes a pointer to an already allocated (possibly stack)
 * ObjectAddressCollector struct. It makes sure this struct is ready to be used for object
 * collection.
 *
 * If an already initialized collector is passed the collector will be cleared from its
 * contents to be reused.
 */
static void
InitObjectAddressCollector(ObjectAddressCollector *collector)
{
	assert_valid_hash_key3(ObjectAddress, classId, objectId, objectSubId);
	collector->dependencySet = CreateSimpleHashSetWithName(ObjectAddress,
														   "dependency set");
	collector->dependencyList = NULL;

	collector->visitedObjects = CreateSimpleHashSetWithName(ObjectAddress,
															"visited object set");
}


/*
 * TargetObjectVisited returns true if the input target has been visited while
 * traversing pg_depend.
 */
static bool
TargetObjectVisited(ObjectAddressCollector *collector, ObjectAddress target)
{
	bool found = false;

	/* find in set */
	hash_search(collector->visitedObjects, &target, HASH_FIND, &found);

	return found;
}


/*
 * MarkObjectVisited marks the object as visited during the traversal of
 * pg_depend.
 */
static void
MarkObjectVisited(ObjectAddressCollector *collector, ObjectAddress target)
{
	bool found = false;

	/* add to set */
	ObjectAddress *address = (ObjectAddress *) hash_search(collector->visitedObjects,
														   &target,
														   HASH_ENTER, &found);

	if (!found)
	{
		/* copy object address in */
		*address = target;
	}
}


/*
 * CollectObjectAddress adds an ObjectAddress to the collector.
 */
static void
CollectObjectAddress(ObjectAddressCollector *collector, const ObjectAddress *collect)
{
	bool found = false;

	/* add to set */
	ObjectAddress *address = (ObjectAddress *) hash_search(collector->dependencySet,
														   collect,
														   HASH_ENTER, &found);

	if (!found)
	{
		/* copy object address in */
		*address = *collect;
	}

	/* add to list*/
	collector->dependencyList = lappend(collector->dependencyList, address);
}


/*
 * IsObjectAddressCollected is a helper function that can check if an ObjectAddress is
 * already in a (unsorted) list of ObjectAddresses
 */
static bool
IsObjectAddressCollected(ObjectAddress findAddress,
						 ObjectAddressCollector *collector)
{
	bool found = false;

	/* add to set */
	hash_search(collector->dependencySet, &findAddress, HASH_FIND, &found);

	return found;
}


/*
 * SupportedDependencyByCitus returns whether citus has support to distribute the object
 * addressed.
 */
bool
SupportedDependencyByCitus(const ObjectAddress *address)
{
	if (!EnableMetadataSync)
	{
		/*
		 * If the user has disabled object propagation we need to fall back to the legacy
		 * behaviour in which we only support schema creation
		 */
		switch (getObjectClass(address))
		{
			case OCLASS_SCHEMA:
			{
				return !isTempNamespace(address->objectId);
			}

			default:
			{
				return false;
			}
		}

		/* should be unreachable */
		Assert(false);
	}

	/*
	 * looking at the type of a object to see if we know how to create the object on the
	 * workers.
	 */
	switch (getObjectClass(address))
	{
		case OCLASS_AM:
		{
			/*
			 * Only support access methods if they came from extensions
			 * During the dependency resolution it will cascade into the extension and
			 * distributed that one instead of the Access Method. Now access methods can
			 * be configured on tables on the workers.
			 */
			return IsObjectAddressOwnedByExtension(address, NULL);
		}

		case OCLASS_CONSTRAINT:
		{
			/*
			 * Constraints are only supported when on domain types. Other constraints have
			 * their typid set to InvalidOid.
			 */
			return OidIsValid(get_constraint_typid(address->objectId));
		}

		case OCLASS_COLLATION:
		{
			return true;
		}

		case OCLASS_SCHEMA:
		{
			return !isTempNamespace(address->objectId);
		}

		case OCLASS_PROC:
		{
			return true;
		}

		case OCLASS_DATABASE:
		{
			return true;
		}

		case OCLASS_FOREIGN_SERVER:
		{
			return true;
		}

		case OCLASS_ROLE:
		{
			/* if it is a reserved role do not propagate */
			if (IsReservedName(GetUserNameFromId(address->objectId, false)))
			{
				return false;
			}

			return true;
		}

		case OCLASS_EXTENSION:
		{
			return true;
		}

		case OCLASS_PUBLICATION:
		{
			return true;
		}

		case OCLASS_TSCONFIG:
		{
			return true;
		}

		case OCLASS_TSDICT:
		{
			return true;
		}

		case OCLASS_TYPE:
		{
			switch (get_typtype(address->objectId))
			{
				case TYPTYPE_ENUM:
				case TYPTYPE_COMPOSITE:
				case TYPTYPE_DOMAIN:
				{
					return true;
				}

				case TYPTYPE_BASE:
				{
					/*
					 * array types should be followed but not created, as they get created
					 * by the original type.
					 */
					return type_is_array(address->objectId);
				}

				default:
				{
					/* type not supported */
					return false;
				}
			}

			/*
			 * should be unreachable, break here is to make sure the function has a path
			 * without return, instead of falling through to the next block */
			break;
		}

		case OCLASS_CLASS:
		{
			char relKind = get_rel_relkind(address->objectId);

			/*
			 * composite types have a reference to a relation of composite type, we need
			 * to follow those to get the dependencies of type fields.
			 *
			 * As we also handle tables as objects as well, follow dependencies
			 * for tables.
			 */
			if (relKind == RELKIND_COMPOSITE_TYPE ||
				relKind == RELKIND_RELATION ||
				relKind == RELKIND_PARTITIONED_TABLE ||
				relKind == RELKIND_FOREIGN_TABLE ||
				relKind == RELKIND_SEQUENCE ||
				relKind == RELKIND_INDEX ||
				relKind == RELKIND_PARTITIONED_INDEX ||
				relKind == RELKIND_VIEW)
			{
				return true;
			}

			return false;
		}

		default:
		{
			/* unsupported type */
			return false;
		}
	}
}


/*
 * ErrorOrWarnIfObjectHasUnsupportedDependency returns false without throwing any message if
 * object doesn't have any unsupported dependency, else throws a message with proper level
 * (except the cluster doesn't have any node) and return true.
 */
static bool
ErrorOrWarnIfObjectHasUnsupportedDependency(const ObjectAddress *objectAddress)
{
	DeferredErrorMessage *errMsg = DeferErrorIfHasUnsupportedDependency(objectAddress);
	if (errMsg != NULL)
	{
		/*
		 * Don't need to give any messages if there is no worker nodes in
		 * the cluster as user's experience won't be affected on the single node even
		 * if the object won't be distributed.
		 */
		if (!HasAnyNodes())
		{
			return true;
		}

		/*
		 * Since Citus drops and recreates some object while converting a table type
		 * giving a DEBUG1 message is enough if the process in table type conversion
		 * function call
		 */
		if (InTableTypeConversionFunctionCall)
		{
			RaiseDeferredError(errMsg, DEBUG1);
		}
		/*
		 * If the view is object distributed, we should provide an error to not have
		 * different definition of object on coordinator and worker nodes. If the object
		 * is not distributed yet, we can create it locally to not affect user's local
		 * usage experience.
		 */
		else if (IsAnyObjectDistributed(list_make1((ObjectAddress *) objectAddress)))
		{
			RaiseDeferredError(errMsg, ERROR);
		}
		else
		{
			if (EnableUnsupportedFeatureMessages)
			{
				RaiseDeferredError(errMsg, WARNING);
			}
		}

		return true;
	}

	return false;
}


/*
 * ErrorOrWarnIfAnyObjectHasUnsupportedDependency iteratively calls
 * ErrorOrWarnIfObjectHasUnsupportedDependency for given addresses.
 */
bool
ErrorOrWarnIfAnyObjectHasUnsupportedDependency(List *objectAddresses)
{
	ObjectAddress *objectAddress = NULL;
	foreach_declared_ptr(objectAddress, objectAddresses)
	{
		if (ErrorOrWarnIfObjectHasUnsupportedDependency(objectAddress))
		{
			return true;
		}
	}

	return false;
}


/*
 * DeferErrorIfHasUnsupportedDependency returns deferred error message if the given
 * object has any undistributable dependency.
 */
static DeferredErrorMessage *
DeferErrorIfHasUnsupportedDependency(const ObjectAddress *objectAddress)
{
	ObjectAddress *undistributableDependency = GetUndistributableDependency(
		objectAddress);

	if (undistributableDependency == NULL)
	{
		return NULL;
	}

	StringInfo errorInfo = makeStringInfo();
	StringInfo detailInfo = makeStringInfo();

	char *objectDescription = getObjectDescription(objectAddress, false);
	char *dependencyDescription = getObjectDescription(undistributableDependency, false);

	/*
	 * We expect callers to interpret the error returned from this function
	 * as a warning if the object itself is just being created. In that case,
	 * we expect them to report below error detail as well to indicate that
	 * object itself will not be propagated but will still be created locally.
	 *
	 * Otherwise, callers are expected to throw the error returned from this
	 * function as a hard one by ignoring the detail part.
	 */
	if (!IsAnyObjectDistributed(list_make1((ObjectAddress *) objectAddress)))
	{
		appendStringInfo(detailInfo, "\"%s\" will be created only locally",
						 objectDescription);
	}

	if (SupportedDependencyByCitus(undistributableDependency))
	{
		StringInfo hintInfo = makeStringInfo();

		appendStringInfo(errorInfo, "\"%s\" has dependency to \"%s\" that is not in "
									"Citus' metadata",
						 objectDescription,
						 dependencyDescription);

		if (IsAnyObjectDistributed(list_make1((ObjectAddress *) objectAddress)))
		{
			appendStringInfo(hintInfo,
							 "Distribute \"%s\" first to modify \"%s\" on worker nodes",
							 dependencyDescription,
							 objectDescription);
		}
		else
		{
			appendStringInfo(hintInfo, "Distribute \"%s\" first to distribute \"%s\"",
							 dependencyDescription,
							 objectDescription);
		}

		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
							 errorInfo->data, detailInfo->data, hintInfo->data);
	}

	appendStringInfo(errorInfo, "\"%s\" has dependency on unsupported "
								"object \"%s\"", objectDescription,
					 dependencyDescription);

	return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
						 errorInfo->data, detailInfo->data, NULL);
}


/*
 * DeferErrorIfAnyObjectHasUnsupportedDependency iteratively calls
 * DeferErrorIfHasUnsupportedDependency for given addresses.
 */
DeferredErrorMessage *
DeferErrorIfAnyObjectHasUnsupportedDependency(const List *objectAddresses)
{
	DeferredErrorMessage *deferredErrorMessage = NULL;
	ObjectAddress *objectAddress = NULL;
	foreach_declared_ptr(objectAddress, objectAddresses)
	{
		deferredErrorMessage = DeferErrorIfHasUnsupportedDependency(objectAddress);
		if (deferredErrorMessage)
		{
			return deferredErrorMessage;
		}
	}

	return NULL;
}


/*
 * GetUndistributableDependency checks whether object has any non-distributable
 * dependency. If any one found, it will be returned.
 */
static ObjectAddress *
GetUndistributableDependency(const ObjectAddress *objectAddress)
{
	List *dependencies = GetAllDependenciesForObject(objectAddress);
	ObjectAddress *dependency = NULL;

	/*
	 * Users can disable metadata sync by their own risk. If it is disabled, Citus
	 * doesn't propagate dependencies. So, if it is disabled, there is no undistributable
	 * dependency.
	 */
	if (!EnableMetadataSync)
	{
		return NULL;
	}

	foreach_declared_ptr(dependency, dependencies)
	{
		/*
		 * Objects with the id smaller than FirstNormalObjectId should be created within
		 * initdb. Citus needs to have such objects as distributed, so we can not add
		 * such check to dependency resolution logic. Though, Citus shouldn't error
		 * out if such dependency is not supported. So, skip them here.
		 */
		if (dependency->objectId < FirstNormalObjectId)
		{
			continue;
		}

		/*
		 * If object is distributed already, ignore it.
		 */
		if (IsAnyObjectDistributed(list_make1(dependency)))
		{
			continue;
		}

		/*
		 * If the dependency is not supported with Citus, return the dependency.
		 */
		if (!SupportedDependencyByCitus(dependency))
		{
			/*
			 * Since we do not yet support distributed TS TEMPLATE and AM objects, we skip
			 * dependency checks for text search templates. The user is expected to
			 * manually create the TS TEMPLATE and AM objects.
			 */
			if (getObjectClass(dependency) != OCLASS_TSTEMPLATE &&
				getObjectClass(dependency) != OCLASS_AM)
			{
				return dependency;
			}
		}

		if (getObjectClass(dependency) == OCLASS_CLASS)
		{
			char relKind = get_rel_relkind(dependency->objectId);

			if (relKind == RELKIND_SEQUENCE ||
				relKind == RELKIND_COMPOSITE_TYPE ||
				relKind == RELKIND_VIEW)
			{
				/* citus knows how to auto-distribute these dependencies */
				continue;
			}
			else if (relKind == RELKIND_INDEX || relKind == RELKIND_PARTITIONED_INDEX)
			{
				/*
				 * Indexes are only qualified for distributed objects for dependency
				 * tracking purposes, so we can ignore those.
				 */
				continue;
			}
			else
			{
				/*
				 * Citus doesn't know how to auto-distribute the rest of the RELKINDs
				 * via dependency resolution
				 */
				return dependency;
			}
		}
	}

	return NULL;
}


/*
 * IsTableOwnedByExtension returns whether the table with the given relation ID is
 * owned by an extension.
 */
bool
IsTableOwnedByExtension(Oid relationId)
{
	ObjectAddress tableAddress = { 0 };
	ObjectAddressSet(tableAddress, RelationRelationId, relationId);

	return IsObjectAddressOwnedByExtension(&tableAddress, NULL);
}


/*
 * ObjectAddressDependsOnExtension returns whether or not the object depends
 * on an extension. It is assumed that "an object having a dependency of type
 * DEPENDENCY_AUTO_EXTENSION to an extension" depends on that extension.
 */
bool
ObjectAddressDependsOnExtension(const ObjectAddress *target)
{
	return ObjectAddressHasExtensionDependency(target, NULL,
											   DEPENDENCY_AUTO_EXTENSION);
}


/*
 * IsObjectAddressOwnedByExtension returns whether or not the object is owned by an
 * extension. It is assumed that an object having a dependency on an extension is created
 * by that extension and therefore owned by that extension.
 *
 * If extensionAddress is not set to a NULL pointer the function will write the extension
 * address this function depends on into this location.
 */
static bool
IsObjectAddressOwnedByExtension(const ObjectAddress *target,
								ObjectAddress *extensionAddress)
{
	return ObjectAddressHasExtensionDependency(target, extensionAddress,
											   DEPENDENCY_EXTENSION);
}


/*
 * ObjectAddressHasExtensionDependency is a helper function that returns true if
 * given object has a dependency record (of type DEPENDENCY_EXTENSION or
 * DEPENDENCY_AUTO_EXTENSION) for an extension.
 *
 * If extensionAddress is not set to a NULL pointer the function will write the
 * extension address this function depends on into this location.
 */
static bool
ObjectAddressHasExtensionDependency(const ObjectAddress *target,
									ObjectAddress *extensionAddress,
									int extensionDependency)
{
	Assert(extensionDependency == DEPENDENCY_EXTENSION ||
		   extensionDependency == DEPENDENCY_AUTO_EXTENSION);

	ScanKeyData key[2];
	HeapTuple depTup = NULL;
	bool result = false;

	Relation depRel = table_open(DependRelationId, AccessShareLock);

	/* scan pg_depend for classid = $1 AND objid = $2 using pg_depend_depender_index */
	ScanKeyInit(&key[0], Anum_pg_depend_classid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target->classId));
	ScanKeyInit(&key[1], Anum_pg_depend_objid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(target->objectId));
	SysScanDesc depScan = systable_beginscan(depRel, DependDependerIndexId, true, NULL, 2,
											 key);

	while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
	{
		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
		if (pg_depend->deptype == extensionDependency)
		{
			result = true;
			if (extensionAddress != NULL)
			{
				ObjectAddressSubSet(*extensionAddress, pg_depend->refclassid,
									pg_depend->refobjid, pg_depend->refobjsubid);
			}
			break;
		}
	}

	systable_endscan(depScan);
	table_close(depRel, AccessShareLock);

	return result;
}


/*
 * IsAnyObjectAddressOwnedByExtension iteratively calls IsObjectAddressOwnedByExtension
 * for given addresses to determine if any address is owned by an extension.
 */
bool
IsAnyObjectAddressOwnedByExtension(const List *targets,
								   ObjectAddress *extensionAddress)
{
	ObjectAddress *target = NULL;
	foreach_declared_ptr(target, targets)
	{
		if (IsObjectAddressOwnedByExtension(target, extensionAddress))
		{
			return true;
		}
	}

	return false;
}


/*
 * FirstExtensionWithSchema returns the first extension address whose schema is the same
 * as given schema. If no extension depends on the schema, it returns NULL.
 * i.e. decide if given schema is an extension schema as in
 *  `CREATE EXTENSION <ext> [WITH] SCHEMA <schema>;`
 */
ObjectAddress *
FirstExtensionWithSchema(Oid schemaId)
{
	ObjectAddress *extensionAddress = NULL;

	Relation relation = table_open(ExtensionRelationId, AccessShareLock);

	ScanKeyData entry[1];
	ScanKeyInit(&entry[0], Anum_pg_extension_extnamespace, BTEqualStrategyNumber,
				F_OIDEQ, ObjectIdGetDatum(schemaId));

	SysScanDesc scan = systable_beginscan(relation, InvalidOid, false, NULL, 1, entry);
	HeapTuple extensionTuple = systable_getnext(scan);
	if (HeapTupleIsValid(extensionTuple))
	{
		int extensionIdIndex = Anum_pg_extension_oid;
		TupleDesc tupleDescriptor = RelationGetDescr(relation);
		bool isNull = false;
		Datum extensionIdDatum = heap_getattr(extensionTuple, extensionIdIndex,
											  tupleDescriptor, &isNull);
		Oid extensionId = DatumGetObjectId(extensionIdDatum);

		extensionAddress = palloc0(sizeof(ObjectAddress));
		extensionAddress->objectId = extensionId;
		extensionAddress->classId = ExtensionRelationId;
		extensionAddress->objectSubId = 0;
	}

	systable_endscan(scan);
	table_close(relation, AccessShareLock);

	return extensionAddress;
}


/*
 * IsObjectAddressOwnedByCitus returns true if the given object address
 * is owned by the citus or citus_columnar extensions.
 */
bool
IsObjectAddressOwnedByCitus(const ObjectAddress *objectAddress)
{
	Oid citusId = get_extension_oid("citus", true);
	Oid citusColumnarId = get_extension_oid("citus_columnar", true);

	/* return false because we could not find any citus extension */
	if (!OidIsValid(citusId) && !OidIsValid(citusColumnarId))
	{
		return false;
	}

	ObjectAddress extObjectAddress = InvalidObjectAddress;
	bool ownedByExt = IsObjectAddressOwnedByExtension(objectAddress,
													  &extObjectAddress);
	if (!ownedByExt)
	{
		return false;
	}

	bool ownedByCitus = extObjectAddress.objectId == citusId;
	bool ownedByCitusColumnar = extObjectAddress.objectId == citusColumnarId;

	return ownedByCitus || ownedByCitusColumnar;
}


/*
 * FollowNewSupportedDependencies applies filters on pg_depend entries to follow all
 * objects which should be distributed before the root object can safely be created.
 */
static bool
FollowNewSupportedDependencies(ObjectAddressCollector *collector,
							   DependencyDefinition *definition)
{
	if (definition->mode == DependencyPgDepend)
	{
		/*
		 *  For dependencies found in pg_depend:
		 *
		 *  Follow only normal and extension dependencies. The latter is used to reach the
		 *  extensions, the objects that directly depend on the extension are eliminated
		 *  during the "apply" phase.
		 *
		 *  Other dependencies are internal dependencies and managed by postgres.
		 */
		if (definition->data.pg_depend.deptype != DEPENDENCY_NORMAL &&
			definition->data.pg_depend.deptype != DEPENDENCY_EXTENSION)
		{
			return false;
		}
	}

	/* rest of the tests are to see if we want to follow the actual dependency */
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * If the object is already in our dependency list we do not have to follow any
	 * further
	 */
	if (IsObjectAddressCollected(address, collector))
	{
		return false;
	}

	/*
	 * If the object is already distributed it is not a `new` object that needs to be
	 * distributed before we create a dependent object
	 */
	ObjectAddress *copyAddress = palloc0(sizeof(ObjectAddress));
	*copyAddress = address;
	if (IsAnyObjectDistributed(list_make1(copyAddress)))
	{
		return false;
	}

	/*
	 * We can only distribute dependencies that citus knows how to distribute.
	 *
	 * But we don't want to bail out if the object is owned by extension, because
	 * Citus can create the extension.
	 */
	if (!SupportedDependencyByCitus(&address) &&
		!IsObjectAddressOwnedByExtension(&address, NULL))
	{
		return false;
	}

	if (CitusExtensionObject(&address))
	{
		/* following citus extension could complicate role management */
		return false;
	}

	return true;
}


/*
 * FollowAllSupportedDependencies applies filters on pg_depend entries to follow the
 * dependency tree of objects in depth first order. We will visit all supported objects.
 * This is used to sort a list of dependencies in dependency order.
 */
static bool
FollowAllSupportedDependencies(ObjectAddressCollector *collector,
							   DependencyDefinition *definition)
{
	if (definition->mode == DependencyPgDepend)
	{
		/*
		 *  For dependencies found in pg_depend:
		 *
		 *  Follow only normal and extension dependencies. The latter is used to reach the
		 *  extensions, the objects that directly depend on the extension are eliminated
		 *  during the "apply" phase.
		 *
		 *  Other dependencies are internal dependencies and managed by postgres.
		 */
		if (definition->data.pg_depend.deptype != DEPENDENCY_NORMAL &&
			definition->data.pg_depend.deptype != DEPENDENCY_EXTENSION)
		{
			return false;
		}
	}

	/* rest of the tests are to see if we want to follow the actual dependency */
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * If the object is already in our dependency list we do not have to follow any
	 * further
	 */
	if (IsObjectAddressCollected(address, collector))
	{
		return false;
	}

	/*
	 * We can only distribute dependencies that citus knows how to distribute.
	 *
	 * But we don't want to bail out if the object is owned by extension, because
	 * Citus can create the extension.
	 */
	if (!SupportedDependencyByCitus(&address) &&
		!IsObjectAddressOwnedByExtension(&address, NULL))
	{
		return false;
	}

	if (CitusExtensionObject(&address))
	{
		/* following citus extension could complicate role management */
		return false;
	}

	return true;
}


/*
 * FollowAllDependencies applies filters on pg_depend entries to follow the dependency
 * tree of objects in depth first order. We will visit all objects irrespective of it is
 * supported by Citus or not.
 */
static bool
FollowAllDependencies(ObjectAddressCollector *collector,
					  DependencyDefinition *definition)
{
	if (definition->mode == DependencyPgDepend)
	{
		/*
		 *  For dependencies found in pg_depend:
		 *
		 *  Follow only normal and extension dependencies. The latter is used to reach the
		 *  extensions, the objects that directly depend on the extension are eliminated
		 *  during the "apply" phase.
		 *
		 *  Other dependencies are internal dependencies and managed by postgres.
		 */
		if (definition->data.pg_depend.deptype != DEPENDENCY_NORMAL &&
			definition->data.pg_depend.deptype != DEPENDENCY_EXTENSION)
		{
			return false;
		}
	}

	/* rest of the tests are to see if we want to follow the actual dependency */
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * If the object is already in our dependency list we do not have to follow any
	 * further
	 */
	if (IsObjectAddressCollected(address, collector))
	{
		return false;
	}

	if (CitusExtensionObject(&address))
	{
		/* following citus extension could complicate role management */
		return false;
	}

	return true;
}


/*
 * FollowExtAndInternalDependencies applies filters on pg_depend entries to follow
 * the dependency tree of objects in depth first order. We will visit all objects
 * irrespective of it is supported by Citus or not and it is internal or not.
 */
static bool
FollowExtAndInternalDependencies(ObjectAddressCollector *collector,
								 DependencyDefinition *definition)
{
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * If the object is already in our dependency list we do not have to follow any
	 * further
	 */
	if (IsObjectAddressCollected(address, collector))
	{
		return false;
	}

	if (CitusExtensionObject(&address))
	{
		/*
		 * We do not need to follow citus extension because the purpose
		 * of our walk is to find if an object is owned by citus.
		 */
		return false;
	}

	return true;
}


/*
 * ApplyAddToDependencyList is an apply function for RecurseObjectDependencies that will
 * collect all the ObjectAddresses for pg_depend entries to the context, except it is
 * extension owned one.
 *
 * The context here is assumed to be a (ObjectAddressCollector *) to the location where
 * all ObjectAddresses will be collected.
 */
static void
ApplyAddToDependencyList(ObjectAddressCollector *collector,
						 DependencyDefinition *definition)
{
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * Objects owned by an extension are assumed to be created on the workers by creating
	 * the extension in the cluster, we we don't want explicitly create them.
	 *
	 * Since we do need to capture the extension as a dependency we are following the
	 * object instead of breaking the traversal there.
	 */
	if (IsObjectAddressOwnedByExtension(&address, NULL))
	{
		return;
	}

	CollectObjectAddress(collector, &address);
}


/*
 * ApplyAddCitusDependedObjectsToDependencyList is an apply function for
 * RecurseObjectDependencies that will collect all the ObjectAddresses for
 * pg_depend entries to the context if it is citus extension owned one.
 *
 * The context here is assumed to be a (ObjectAddressCollector *) to the location where
 * all ObjectAddresses will be collected.
 */
static void
ApplyAddCitusDependedObjectsToDependencyList(ObjectAddressCollector *collector,
											 DependencyDefinition *definition)
{
	ObjectAddress address = DependencyDefinitionObjectAddress(definition);

	/*
	 * We only collect the object if it is owned by citus extension.
	 */
	if (IsObjectAddressOwnedByCitus(&address))
	{
		CollectObjectAddress(collector, &address);
	}
}


/*
 * ExpandCitusSupportedTypes base on supported types by citus we might want to expand
 * the list of objects to visit in pg_depend.
 *
 * An example where we want to expand is for types. Their dependencies are not captured
 * with an entry in pg_depend from their object address, but by the object address of the
 * relation describing the type.
 */
static List *
ExpandCitusSupportedTypes(ObjectAddressCollector *collector, ObjectAddress target)
{
	List *result = NIL;

	switch (target.classId)
	{
		case AuthIdRelationId:
		{
			/*
			 * Roles are members of other roles. These relations are not recorded directly
			 * but can be deduced from pg_auth_members
			 */
			return ExpandRolesToGroups(target.objectId);
		}

		case ExtensionRelationId:
		{
			/*
			 * FDWs get propagated along with the extensions they belong to.
			 * In case there are GRANTed privileges on FDWs to roles, those
			 * GRANT statements will be propagated to. In order to make sure
			 * that those GRANT statements work, the privileged roles should
			 * exist on the worker nodes. Hence, here we find these dependent
			 * roles and add them as dependencies.
			 */

			Oid extensionId = target.objectId;
			List *FDWOids = GetDependentFDWsToExtension(extensionId);

			Oid FDWOid = InvalidOid;
			foreach_declared_oid(FDWOid, FDWOids)
			{
				List *dependentRoleIds = GetDependentRoleIdsFDW(FDWOid);
				List *dependencies =
					CreateObjectAddressDependencyDefList(AuthIdRelationId,
														 dependentRoleIds);
				result = list_concat(result, dependencies);
			}

			break;
		}

		case TypeRelationId:
		{
			switch (get_typtype(target.objectId))
			{
				/*
				 * types depending on other types are not captured in pg_depend, instead
				 * they are described with their dependencies by the relation that
				 * describes the composite type.
				 */
				case TYPTYPE_COMPOSITE:
				{
					Oid typeRelationId = get_typ_typrelid(target.objectId);
					DependencyDefinition *dependency =
						CreateObjectAddressDependencyDef(RelationRelationId,
														 typeRelationId);
					result = lappend(result, dependency);
					break;
				}

				/*
				 * Domains can have constraints associated with them. Constraints themself
				 * can depend on things like functions. To support the propagation of
				 * these functions we will add the constraints to the list of objects to
				 * be created.
				 */
				case TYPTYPE_DOMAIN:
				{
					List *dependencies =
						GetTypeConstraintDependencyDefinition(target.objectId);
					result = list_concat(result, dependencies);
					break;
				}
			}

			/*
			 * array types don't have a normal dependency on their element type, instead
			 * their dependency is an internal one. We can't follow interal dependencies
			 * as that would cause a cyclic dependency on others, instead we expand here
			 * to follow the dependency on the element type.
			 */
			if (type_is_array(target.objectId))
			{
				Oid typeId = get_element_type(target.objectId);
				DependencyDefinition *dependency =
					CreateObjectAddressDependencyDef(TypeRelationId, typeId);
				result = lappend(result, dependency);
			}

			break;
		}

		case RelationRelationId:
		{
			/*
			 * Triggers both depend to the relations and to the functions they
			 * execute. Also, pg_depend records dependencies from triggers to the
			 * functions but not from relations to their triggers. Given above two,
			 * we directly expand depencies for the relations to trigger functions.
			 * That way, we won't attempt to create the trigger as a dependency of
			 * the relation, which would fail as the relation itself is not created
			 * yet when ensuring dependencies.
			 */
			Oid relationId = target.objectId;
			List *triggerFunctionDepencyList =
				GetRelationTriggerFunctionDependencyList(relationId);
			result = list_concat(result, triggerFunctionDepencyList);

			/*
			 * Statistics' both depend to the relations and to the schemas they belong
			 * to. Also, pg_depend records dependencies from statistics to their schemas
			 * but not from relations to their statistics' schemas. Given above two,
			 * we directly expand dependencies for the relations to schemas of
			 * statistics.
			 */
			List *statisticsSchemaDependencyList =
				GetRelationStatsSchemaDependencyList(relationId);
			result = list_concat(result, statisticsSchemaDependencyList);

			/*
			 * Get the dependent sequences for tables (both as serial columns and
			 * columns have nextval with existing sequences) and expand dependency list
			 * with them.
			 */
			List *sequenceDependencyList = GetRelationSequenceDependencyList(relationId);
			result = list_concat(result, sequenceDependencyList);

			/*
			 * Get the dependent functions for tables as columns has default values
			 * and contraints, then expand dependency list with them.
			 */
			List *functionDependencyList = GetRelationFunctionDependencyList(relationId);
			result = list_concat(result, functionDependencyList);

			/*
			 * Tables could have indexes. Indexes themself could have dependencies that
			 * need to be propagated. eg. TEXT SEARCH CONFIGURATIONS. Here we add the
			 * addresses of all indices to the list of objects to vist, as to make sure we
			 * create all objects required by the indices before we create the table
			 * including indices.
			 */
			List *indexDependencyList = GetRelationIndicesDependencyList(relationId);
			result = list_concat(result, indexDependencyList);

			/*
			 * Get the dependencies of the rule for the given view. PG keeps internal
			 * dependency between view and rule. As it is stated on the PG doc, if
			 * there is an internal dependency, dependencies of the dependent object
			 * behave much like they were dependencies of the referenced object.
			 *
			 * We need to expand dependencies by including dependencies of the rule
			 * internally dependent to the view. PG doesn't keep any dependencies
			 * from view to any object, but it keeps an internal dependency to the
			 * rule and that rule has dependencies to other objects.
			 */
			char relKind = get_rel_relkind(relationId);
			if (relKind == RELKIND_VIEW || relKind == RELKIND_MATVIEW)
			{
				List *ruleRefDepList = GetViewRuleReferenceDependencyList(relationId);
				result = list_concat(result, ruleRefDepList);
			}

			break;
		}

		case PublicationRelationId:
		{
			Oid publicationId = target.objectId;

			/*
			 * Publications do not depend directly on relations, because dropping
			 * the relation will only remove it from the publications. However,
			 * we add a dependency to ensure the relation is created first when
			 * adding a node.
			 */
			List *relationDependencyList =
				GetPublicationRelationsDependencyList(publicationId);
			result = list_concat(result, relationDependencyList);

			/*
			 * As of PostgreSQL 15, the same applies to schemas.
			 */
			List *schemaIdList =
				GetPublicationSchemas(publicationId);
			List *schemaDependencyList =
				CreateObjectAddressDependencyDefList(NamespaceRelationId, schemaIdList);
			result = list_concat(result, schemaDependencyList);

			break;
		}

		default:
		{
			/* no expansion for unsupported types */
			break;
		}
	}
	return result;
}


/*
 * ExpandForPgVanilla only expands only comosite types because other types
 * will find their dependencies in pg_depend. The method should only be called by
 * is_citus_depended_object udf.
 */
static List *
ExpandForPgVanilla(ObjectAddressCollector *collector,
				   ObjectAddress target)
{
	/* should only be called if GUC is enabled */
	Assert(HideCitusDependentObjects == true);

	List *result = NIL;

	if (target.classId == TypeRelationId && get_typtype(target.objectId) ==
		TYPTYPE_COMPOSITE)
	{
		/*
		 * types depending on other types are not captured in pg_depend, instead
		 * they are described with their dependencies by the relation that
		 * describes the composite type.
		 */
		Oid typeRelationId = get_typ_typrelid(target.objectId);
		DependencyDefinition *dependency =
			CreateObjectAddressDependencyDef(RelationRelationId,
											 typeRelationId);
		result = lappend(result, dependency);
	}

	return result;
}


/*
 * GetDependentRoleIdsFDW returns a list of role oids that has privileges on the
 * FDW with the given object id.
 */
static List *
GetDependentRoleIdsFDW(Oid FDWOid)
{
	List *roleIds = NIL;

	Acl *aclEntry = GetPrivilegesForFDW(FDWOid);

	if (aclEntry == NULL)
	{
		return NIL;
	}

	AclItem *privileges = ACL_DAT(aclEntry);
	int numberOfPrivsGranted = ACL_NUM(aclEntry);

	for (int i = 0; i < numberOfPrivsGranted; i++)
	{
		roleIds = lappend_oid(roleIds, privileges[i].ai_grantee);
	}

	return roleIds;
}


/*
 * ExpandRolesToGroups returns a list of object addresses pointing to roles that roleid
 * depends on.
 */
static List *
ExpandRolesToGroups(Oid roleid)
{
	Relation pgAuthMembers = table_open(AuthMemRelationId, AccessShareLock);
	HeapTuple tuple = NULL;

	ScanKeyData scanKey[1];
	const int scanKeyCount = 1;

	/* scan pg_auth_members for member = $1 via index pg_auth_members_member_role_index */
	ScanKeyInit(&scanKey[0], Anum_pg_auth_members_member, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(roleid));

	SysScanDesc scanDescriptor = systable_beginscan(pgAuthMembers, AuthMemMemRoleIndexId,
													true, NULL, scanKeyCount, scanKey);

	List *roles = NIL;
	while ((tuple = systable_getnext(scanDescriptor)) != NULL)
	{
		Form_pg_auth_members membership = (Form_pg_auth_members) GETSTRUCT(tuple);

		DependencyDefinition *definition = palloc0(sizeof(DependencyDefinition));
		definition->mode = DependencyObjectAddress;
		ObjectAddressSet(definition->data.address, AuthIdRelationId, membership->roleid);

		roles = lappend(roles, definition);
	}

	systable_endscan(scanDescriptor);
	table_close(pgAuthMembers, AccessShareLock);

	return roles;
}


/*
 * GetViewRuleReferenceDependencyList returns the dependencies of the view's
 * internal rule dependencies.
 */
static List *
GetViewRuleReferenceDependencyList(Oid viewId)
{
	List *dependencyTupleList = GetPgDependTuplesForDependingObjects(RelationRelationId,
																	 viewId);
	List *nonInternalDependenciesOfDependingRules = NIL;

	HeapTuple depTup = NULL;
	foreach_declared_ptr(depTup, dependencyTupleList)
	{
		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);

		/*
		 * Dependencies of the internal rule dependency should be handled as the dependency
		 * of referenced view object.
		 *
		 * PG doesn't keep dependency relation between views and dependent objects directly
		 * but it keeps an internal dependency relation between the view and the rule, then
		 * keeps the dependent objects of the view as non-internal dependencies of the
		 * internally dependent rule object.
		 */
		if (pg_depend->deptype == DEPENDENCY_INTERNAL && pg_depend->classid ==
			RewriteRelationId)
		{
			ObjectAddress ruleAddress = { 0 };
			ObjectAddressSet(ruleAddress, RewriteRelationId, pg_depend->objid);

			/* Expand results with the noninternal dependencies of it */
			List *ruleDependencies = DependencyDefinitionFromPgDepend(ruleAddress);

			DependencyDefinition *dependencyDef = NULL;
			foreach_declared_ptr(dependencyDef, ruleDependencies)
			{
				/*
				 * Follow all dependencies of the internally dependent rule dependencies
				 * except it is an internal dependency of view itself.
				 */
				if (dependencyDef->data.pg_depend.deptype == DEPENDENCY_INTERNAL ||
					(dependencyDef->data.pg_depend.refclassid == RelationRelationId &&
					 dependencyDef->data.pg_depend.refobjid == viewId))
				{
					continue;
				}

				nonInternalDependenciesOfDependingRules =
					lappend(nonInternalDependenciesOfDependingRules, dependencyDef);
			}
		}
	}

	return nonInternalDependenciesOfDependingRules;
}


/*
 * GetRelationSequenceDependencyList returns the sequence dependency definition
 * list for the given relation.
 */
static List *
GetRelationSequenceDependencyList(Oid relationId)
{
	List *seqInfoList = NIL;
	GetDependentSequencesWithRelation(relationId, &seqInfoList, 0, DEPENDENCY_AUTO);

	List *seqIdList = NIL;
	SequenceInfo *seqInfo = NULL;
	foreach_declared_ptr(seqInfo, seqInfoList)
	{
		seqIdList = lappend_oid(seqIdList, seqInfo->sequenceOid);
	}

	List *sequenceDependencyDefList =
		CreateObjectAddressDependencyDefList(RelationRelationId, seqIdList);

	return sequenceDependencyDefList;
}


/*
 * GetRelationFunctionDependencyList returns the function dependency definition
 * list for the given relation.
 */
static List *
GetRelationFunctionDependencyList(Oid relationId)
{
	List *dependentFunctionOids = GetDependentFunctionsWithRelation(relationId);
	List *functionDependencyDefList =
		CreateObjectAddressDependencyDefList(ProcedureRelationId, dependentFunctionOids);

	return functionDependencyDefList;
}


/*
 * GetRelationStatsSchemaDependencyList returns a list of DependencyDefinition
 * objects for the schemas that statistics' of the relation with relationId depends.
 */
static List *
GetRelationStatsSchemaDependencyList(Oid relationId)
{
	List *schemaIds = GetExplicitStatisticsSchemaIdList(relationId);

	return CreateObjectAddressDependencyDefList(NamespaceRelationId, schemaIds);
}


/*
 * CollectIndexOids implements PGIndexProcessor to create a list of all index oids
 */
static void
CollectIndexOids(Form_pg_index formPgIndex, List **oids, int flags)
{
	*oids = lappend_oid(*oids, formPgIndex->indexrelid);
}


/*
 * GetRelationIndicesDependencyList creates a list of ObjectAddressDependencies for the
 * indexes on a given relation.
 */
static List *
GetRelationIndicesDependencyList(Oid relationId)
{
	List *indexIds = ExecuteFunctionOnEachTableIndex(relationId, CollectIndexOids, 0);
	return CreateObjectAddressDependencyDefList(RelationRelationId, indexIds);
}


/*
 * GetRelationTriggerFunctionDependencyList returns a list of DependencyDefinition
 * objects for the functions that triggers of the relation with relationId depends.
 */
static List *
GetRelationTriggerFunctionDependencyList(Oid relationId)
{
	List *dependencyList = NIL;

	List *triggerIdList = GetExplicitTriggerIdList(relationId);
	Oid triggerId = InvalidOid;
	foreach_declared_oid(triggerId, triggerIdList)
	{
		Oid functionId = GetTriggerFunctionId(triggerId);
		DependencyDefinition *dependency =
			CreateObjectAddressDependencyDef(ProcedureRelationId, functionId);
		dependencyList = lappend(dependencyList, dependency);
	}

	return dependencyList;
}


/*
 * GetPublicationRelationsDependencyList creates a list of ObjectAddressDependencies for
 * a publication on the Citus relations it contains. This helps make sure we distribute
 * Citus tables before local tables.
 */
static List *
GetPublicationRelationsDependencyList(Oid publicationId)
{
	List *allRelationIds = GetPublicationRelations(publicationId, PUBLICATION_PART_ROOT);
	List *citusRelationIds = NIL;

	Oid relationId = InvalidOid;

	foreach_declared_oid(relationId, allRelationIds)
	{
		if (!IsCitusTable(relationId))
		{
			continue;
		}

		citusRelationIds = lappend_oid(citusRelationIds, relationId);
	}

	return CreateObjectAddressDependencyDefList(RelationRelationId, citusRelationIds);
}


/*
 * GetTypeConstraintDependencyDefinition creates a list of constraint dependency
 * definitions for a given type
 */
static List *
GetTypeConstraintDependencyDefinition(Oid typeId)
{
	/* lookup and look all constraints to add them to the CreateDomainStmt */
	Relation conRel = table_open(ConstraintRelationId, AccessShareLock);

	/* Look for CHECK Constraints on this domain */
	ScanKeyData key[1];
	ScanKeyInit(&key[0],
				Anum_pg_constraint_contypid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(typeId));

	SysScanDesc scan = systable_beginscan(conRel, ConstraintTypidIndexId, true, NULL, 1,
										  key);

	List *dependencies = NIL;
	HeapTuple conTup = NULL;
	while (HeapTupleIsValid(conTup = systable_getnext(scan)))
	{
		Form_pg_constraint c = (Form_pg_constraint) GETSTRUCT(conTup);

		if (c->contype != CONSTRAINT_CHECK)
		{
			/* Ignore non-CHECK constraints, shouldn't be any */
			continue;
		}

		dependencies = lappend(dependencies, CreateObjectAddressDependencyDef(
								   ConstraintRelationId, c->oid));
	}

	systable_endscan(scan);
	table_close(conRel, NoLock);

	return dependencies;
}


/*
 * CreateObjectAddressDependencyDef returns DependencyDefinition object that
 * stores the ObjectAddress for the database object identified by classId and
 * objectId.
 */
static DependencyDefinition *
CreateObjectAddressDependencyDef(Oid classId, Oid objectId)
{
	DependencyDefinition *dependency = palloc0(sizeof(DependencyDefinition));
	dependency->mode = DependencyObjectAddress;
	ObjectAddressSet(dependency->data.address, classId, objectId);
	return dependency;
}


/*
 * CreateObjectAddressDependencyDefList is a wrapper function for
 * CreateObjectAddressDependencyDef to operate on a list of relation oids,
 * instead of a single oid.
 */
static List *
CreateObjectAddressDependencyDefList(Oid classId, List *objectIdList)
{
	List *dependencyList = NIL;
	Oid objectId = InvalidOid;
	foreach_declared_oid(objectId, objectIdList)
	{
		DependencyDefinition *dependency =
			CreateObjectAddressDependencyDef(classId, objectId);
		dependencyList = lappend(dependencyList, dependency);
	}

	return dependencyList;
}


/*
 * DependencyDefinitionObjectAddress returns the object address of the dependency defined
 * by the dependency definition, irregardless what the source of the definition is
 */
static ObjectAddress
DependencyDefinitionObjectAddress(DependencyDefinition *definition)
{
	switch (definition->mode)
	{
		case DependencyObjectAddress:
		{
			return definition->data.address;
		}

		case DependencyPgDepend:
		{
			ObjectAddress address = { 0 };
			ObjectAddressSet(address,
							 definition->data.pg_depend.refclassid,
							 definition->data.pg_depend.refobjid);
			return address;
		}

		case DependencyPgShDepend:
		{
			ObjectAddress address = { 0 };
			ObjectAddressSet(address,
							 definition->data.pg_shdepend.refclassid,
							 definition->data.pg_shdepend.refobjid);
			return address;
		}
	}

	ereport(ERROR, (errmsg("unsupported dependency definition mode")));
}


/*
 * BuildViewDependencyGraph gets a relation (or a view) and builds a dependency graph for the
 * depending views.
 */
static ViewDependencyNode *
BuildViewDependencyGraph(Oid relationId, HTAB *nodeMap)
{
	bool found = false;
	ViewDependencyNode *node = (ViewDependencyNode *) hash_search(nodeMap, &relationId,
																  HASH_ENTER, &found);

	if (found)
	{
		return node;
	}

	node->id = relationId;
	node->remainingDependencyCount = 0;
	node->dependingNodes = NIL;

	Oid targetObjectClassId = RelationRelationId;
	Oid targetObjectId = relationId;
	List *dependencyTupleList = GetPgDependTuplesForDependingObjects(targetObjectClassId,
																	 targetObjectId);

	HeapTuple depTup = NULL;
	foreach_declared_ptr(depTup, dependencyTupleList)
	{
		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);

		Oid dependingView = GetDependingView(pg_depend);
		if (dependingView != InvalidOid)
		{
			ViewDependencyNode *dependingNode = BuildViewDependencyGraph(dependingView,
																		 nodeMap);

			node->dependingNodes = lappend(node->dependingNodes, dependingNode);
			dependingNode->remainingDependencyCount++;
		}
	}

	return node;
}


/*
 * GetPgDependTuplesForDependingObjects scans pg_depend for given object and
 * returns a list of heap tuples for the objects depending on it.
 */
List *
GetPgDependTuplesForDependingObjects(Oid targetObjectClassId, Oid targetObjectId)
{
	List *dependencyTupleList = NIL;

	Relation pgDepend = table_open(DependRelationId, AccessShareLock);

	ScanKeyData key[2];
	int scanKeyCount = 2;

	ScanKeyInit(&key[0], Anum_pg_depend_refclassid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(targetObjectClassId));
	ScanKeyInit(&key[1], Anum_pg_depend_refobjid, BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(targetObjectId));

	bool useIndex = true;
	SysScanDesc depScan = systable_beginscan(pgDepend, DependReferenceIndexId,
											 useIndex, NULL, scanKeyCount, key);

	HeapTuple dependencyTuple = NULL;
	while (HeapTupleIsValid(dependencyTuple = systable_getnext(depScan)))
	{
		/* copy the tuple first */
		dependencyTuple = heap_copytuple(dependencyTuple);
		dependencyTupleList = lappend(dependencyTupleList, dependencyTuple);
	}

	systable_endscan(depScan);
	relation_close(pgDepend, NoLock);

	return dependencyTupleList;
}


/*
 * GetDependingViews takes a relation id, finds the views that depend on the relation
 * and returns list of the oids of those views. It recurses on the pg_depend table to
 * find the views that recursively depend on the table.
 *
 * The returned views will have the correct order for creating them, from the point of
 * dependencies between.
 */
List *
GetDependingViews(Oid relationId)
{
	HTAB *nodeMap = CreateSimpleHashWithName(Oid, ViewDependencyNode,
											 "view dependency map (oid)");

	ViewDependencyNode *tableNode = BuildViewDependencyGraph(relationId, nodeMap);

	List *dependingViews = NIL;
	List *nodeQueue = list_make1(tableNode);
	ViewDependencyNode *node = NULL;
	foreach_ptr_append(node, nodeQueue)
	{
		ViewDependencyNode *dependingNode = NULL;
		foreach_declared_ptr(dependingNode, node->dependingNodes)
		{
			ObjectAddress relationAddress = { 0 };
			ObjectAddressSet(relationAddress, RelationRelationId, dependingNode->id);

			/*
			 * This function does not catch views with circular dependencies,
			 * because of the remaining dependency count check below.
			 * Here we check if the view has a circular dependency or not.
			 * If yes, we error out with a message that tells the user that
			 * Citus does not handle circular dependencies.
			 */
			DeferredErrorMessage *depError =
				DeferErrorIfCircularDependencyExists(&relationAddress);
			if (depError != NULL)
			{
				RaiseDeferredError(depError, ERROR);
			}

			dependingNode->remainingDependencyCount--;
			if (dependingNode->remainingDependencyCount == 0)
			{
				nodeQueue = lappend(nodeQueue, dependingNode);
				dependingViews = lappend_oid(dependingViews, dependingNode->id);
			}
		}
	}
	return dependingViews;
}


/*
 * GetDependingView gets a row of pg_depend and returns the oid of the view that is depended.
 * If the depended object is not a rewrite object, the object to rewrite is not a view or it
 * is the same view with the depending one InvalidOid is returned.
 */
Oid
GetDependingView(Form_pg_depend pg_depend)
{
	if (pg_depend->classid != RewriteRelationId)
	{
		return InvalidOid;
	}

	Relation rewriteRel = table_open(RewriteRelationId, AccessShareLock);
	ScanKeyData rkey[1];

	ScanKeyInit(&rkey[0],
				Anum_pg_rewrite_oid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(pg_depend->objid));

	SysScanDesc rscan = systable_beginscan(rewriteRel, RewriteOidIndexId,
										   true, NULL, 1, rkey);

	HeapTuple rewriteTup = systable_getnext(rscan);
	if (!HeapTupleIsValid(rewriteTup))
	{
		/*
		 * This function already verified that objid's classid is
		 * RewriteRelationId, so it should exists. But be on the
		 * safe side.
		 */
		ereport(ERROR, (errmsg("catalog lookup failed for view %u",
							   pg_depend->objid)));
	}

	Form_pg_rewrite pg_rewrite = (Form_pg_rewrite) GETSTRUCT(rewriteTup);

	bool isView = get_rel_relkind(pg_rewrite->ev_class) == RELKIND_VIEW;
	bool isMatView = get_rel_relkind(pg_rewrite->ev_class) == RELKIND_MATVIEW;
	bool isDifferentThanRef = pg_rewrite->ev_class != pg_depend->refobjid;

	Oid dependingView = InvalidOid;
	if ((isView || isMatView) && isDifferentThanRef)
	{
		dependingView = pg_rewrite->ev_class;
	}

	systable_endscan(rscan);
	relation_close(rewriteRel, AccessShareLock);

	return dependingView;
}
