citus/src/backend/distributed/commands/schema.c

/*-------------------------------------------------------------------------
 *
 * schema.c
 *    Commands for creating and altering schemas for distributed tables.
 *
 * Copyright (c) 2018, Citus Data, Inc.
 *
 *-------------------------------------------------------------------------
 */


#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup.h"
#include "access/htup_details.h"
#include "catalog/namespace.h"
#include "catalog/pg_class.h"
#include "distributed/commands.h"
#include <distributed/connection_management.h>
#include "distributed/commands/utility_hook.h"
#include "distributed/metadata_cache.h"
#include <distributed/metadata_sync.h>
#include <distributed/remote_commands.h>
#include <distributed/remote_commands.h>
#include "nodes/parsenodes.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/relcache.h"


/*
 * ProcessDropSchemaStmt invalidates the foreign key cache if any table created
 * under dropped schema involved in any foreign key relationship.
 */
void
ProcessDropSchemaStmt(DropStmt *dropStatement)
{
	Relation pgClass = NULL;
	HeapTuple heapTuple = NULL;
	SysScanDesc scanDescriptor = NULL;
	ScanKeyData scanKey[1];
	int scanKeyCount = 1;
	Oid scanIndexId = InvalidOid;
	bool useIndex = false;
	ListCell *dropSchemaCell;

	if (dropStatement->behavior != DROP_CASCADE)
	{
		return;
	}

	foreach(dropSchemaCell, dropStatement->objects)
	{
		Value *schemaValue = (Value *) lfirst(dropSchemaCell);
		char *schemaString = strVal(schemaValue);

		Oid namespaceOid = get_namespace_oid(schemaString, true);

		if (namespaceOid == InvalidOid)
		{
			continue;
		}

		pgClass = heap_open(RelationRelationId, AccessShareLock);

		ScanKeyInit(&scanKey[0], Anum_pg_class_relnamespace, BTEqualStrategyNumber,
					F_OIDEQ, namespaceOid);
		scanDescriptor = systable_beginscan(pgClass, scanIndexId, useIndex, NULL,
											scanKeyCount, scanKey);

		heapTuple = systable_getnext(scanDescriptor);
		while (HeapTupleIsValid(heapTuple))
		{
			Form_pg_class relationForm = (Form_pg_class) GETSTRUCT(heapTuple);
			char *relationName = NameStr(relationForm->relname);
			Oid relationId = get_relname_relid(relationName, namespaceOid);

			/* we're not interested in non-valid, non-distributed relations */
			if (relationId == InvalidOid || !IsDistributedTable(relationId))
			{
				heapTuple = systable_getnext(scanDescriptor);
				continue;
			}

			/* invalidate foreign key cache if the table involved in any foreign key */
			if (TableReferenced(relationId) || TableReferencing(relationId))
			{
				MarkInvalidateForeignKeyGraph();

				systable_endscan(scanDescriptor);
				heap_close(pgClass, NoLock);
				return;
			}

			heapTuple = systable_getnext(scanDescriptor);
		}

		systable_endscan(scanDescriptor);
		heap_close(pgClass, NoLock);
	}
}


/*
 * PlanAlterObjectSchemaStmt determines whether a given ALTER ... SET SCHEMA
 * statement involves a distributed table and issues a warning if so. Because
 * we do not support distributed ALTER ... SET SCHEMA, this function always
 * returns NIL.
 */
List *
PlanAlterObjectSchemaStmt(AlterObjectSchemaStmt *alterObjectSchemaStmt,
						  const char *alterObjectSchemaCommand)
{
	Oid relationId = InvalidOid;

	if (alterObjectSchemaStmt->relation == NULL)
	{
		return NIL;
	}

	relationId = RangeVarGetRelid(alterObjectSchemaStmt->relation,
								  AccessExclusiveLock,
								  alterObjectSchemaStmt->missing_ok);

	/* first check whether a distributed relation is affected */
	if (!OidIsValid(relationId) || !IsDistributedTable(relationId))
	{
		return NIL;
	}

	/* emit a warning if a distributed relation is affected */
	ereport(WARNING, (errmsg("not propagating ALTER ... SET SCHEMA commands to "
							 "worker nodes"),
					  errhint("Connect to worker nodes directly to manually "
							  "change schemas of affected objects.")));

	return NIL;
}


/*
 * EnsureSchemaExistsOnAllNodes connects to all nodes with citus extension user
 * and creates the schema of the given relationId. The function errors out if the
 * command cannot be executed in any of the worker nodes.
 */
void
EnsureSchemaExistsOnAllNodes(Oid relationId)
{
	List *workerNodeList = ActivePrimaryNodeList();
	ListCell *workerNodeCell = NULL;

	foreach(workerNodeCell, workerNodeList)
	{
		WorkerNode *workerNode = (WorkerNode *) lfirst(workerNodeCell);
		char *nodeName = workerNode->workerName;
		uint32 nodePort = workerNode->workerPort;

		EnsureSchemaExistsOnNode(relationId, nodeName, nodePort);
	}
}


/*
 * EnsureSchemaExistsOnNode connects to one node with citus extension user
 * and creates the schema of the given relationId. The function errors out if the
 * command cannot be executed in the node.
 */
void
EnsureSchemaExistsOnNode(Oid relationId, char *nodeName, int32 nodePort)
{
	uint64 connectionFlag = FORCE_NEW_CONNECTION;
	MultiConnection *connection = NULL;

	/* if the schema creation command is not provided, create it */
	Oid schemaId = get_rel_namespace(relationId);
	char *schemaCreationDDL = CreateSchemaDDLCommand(schemaId);

	/* if the relation lives in public namespace, no need to perform any queries in workers */
	if (schemaCreationDDL == NULL)
	{
		return;
	}

	connection = GetNodeUserDatabaseConnection(connectionFlag, nodeName,
											   nodePort, CitusExtensionOwnerName(), NULL);

	ExecuteCriticalRemoteCommand(connection, schemaCreationDDL);
}