Add a utility to process each table index (#4382)

A utility function is added so that each caller can implement a handler
for each index on a given table. This means that the caller doesn't need
to worry about how to access each index, the only thing that it needs to
do each to implement a function to which each index on the table is
passed iteratively.

src/backend/distributed/commands/index.c

@@ -32,6 +32,7 @@
 #include "distributed/multi_executor.h"
 #include "distributed/multi_physical_planner.h"
 #include "distributed/multi_partitioning_utils.h"
+#include "distributed/namespace_utils.h"
 #include "distributed/resource_lock.h"
 #include "distributed/relation_access_tracking.h"
 #include "distributed/relation_utils.h"
@@ -41,6 +42,7 @@
 #include "nodes/parsenodes.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
+#include "utils/fmgroids.h"
 #include "utils/inval.h"
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
@@ -248,6 +250,50 @@ CreateIndexStmtGetSchemaId(IndexStmt *createIndexStatement)
 }
 
 
+/*
+ * ExecuteFunctionOnEachTableIndex executes the given pgIndexProcessor function on each
+ * index of the given relation.
+ * It returns a list that is filled by the pgIndexProcessor.
+ */
+List *
+ExecuteFunctionOnEachTableIndex(Oid relationId, PGIndexProcessor pgIndexProcessor)
+{
+	List *result = NIL;
+	ScanKeyData scanKey[1];
+	int scanKeyCount = 1;
+
+	PushOverrideEmptySearchPath(CurrentMemoryContext);
+
+	/* open system catalog and scan all indexes that belong to this table */
+	Relation pgIndex = table_open(IndexRelationId, AccessShareLock);
+
+	ScanKeyInit(&scanKey[0], Anum_pg_index_indrelid,
+				BTEqualStrategyNumber, F_OIDEQ, relationId);
+
+	SysScanDesc scanDescriptor = systable_beginscan(pgIndex,
+													IndexIndrelidIndexId, true, /* indexOK */
+													NULL, scanKeyCount, scanKey);
+
+	HeapTuple heapTuple = systable_getnext(scanDescriptor);
+	while (HeapTupleIsValid(heapTuple))
+	{
+		Form_pg_index indexForm = (Form_pg_index) GETSTRUCT(heapTuple);
+		pgIndexProcessor(indexForm, &result);
+
+		heapTuple = systable_getnext(scanDescriptor);
+	}
+
+	/* clean up scan and close system catalog */
+	systable_endscan(scanDescriptor);
+	table_close(pgIndex, AccessShareLock);
+
+	/* revert back to original search_path */
+	PopOverrideSearchPath();
+
+	return result;
+}
+
+
 /*
  * SwitchToSequentialExecutionIfIndexNameTooLong generates the longest index name
  * on the shards of the partitions, and if exceeds the limit switches to the

src/backend/distributed/operations/node_protocol.c

@@ -76,7 +76,8 @@ int NextPlacementId = 0;
 
 static List * GetTableReplicaIdentityCommand(Oid relationId);
 static Datum WorkerNodeGetDatum(WorkerNode *workerNode, TupleDesc tupleDescriptor);
-
+static void GatherIndexAndConstraintDefinitionList(Form_pg_index indexForm,
+												   List **indexDDLEventList);
 
 /* exports for SQL callable functions */
 PG_FUNCTION_INFO_V1(master_get_table_metadata);
@@ -684,70 +685,48 @@ GetPreLoadTableCreationCommands(Oid relationId, bool includeSequenceDefaults)
 List *
 GetTableIndexAndConstraintCommands(Oid relationId)
 {
-	List *indexDDLEventList = NIL;
-	ScanKeyData scanKey[1];
-	int scanKeyCount = 1;
+	return ExecuteFunctionOnEachTableIndex(relationId,
+										   GatherIndexAndConstraintDefinitionList);
+}
 
-	PushOverrideEmptySearchPath(CurrentMemoryContext);
 
-	/* open system catalog and scan all indexes that belong to this table */
-	Relation pgIndex = table_open(IndexRelationId, AccessShareLock);
+/*
+ * GatherIndexAndConstraintDefinitionList adds the DDL command for the given index.
+ */
+static void
+GatherIndexAndConstraintDefinitionList(Form_pg_index indexForm, List **indexDDLEventList)
+{
+	Oid indexId = indexForm->indexrelid;
+	char *statementDef = NULL;
 
-	ScanKeyInit(&scanKey[0], Anum_pg_index_indrelid,
-				BTEqualStrategyNumber, F_OIDEQ, relationId);
+	bool indexImpliedByConstraint = IndexImpliedByAConstraint(indexForm);
 
-	SysScanDesc scanDescriptor = systable_beginscan(pgIndex,
-													IndexIndrelidIndexId,
-													true, /* indexOK */
-													NULL, scanKeyCount, scanKey);
-
-	HeapTuple heapTuple = systable_getnext(scanDescriptor);
-	while (HeapTupleIsValid(heapTuple))
+	/* get the corresponding constraint or index statement */
+	if (indexImpliedByConstraint)
 	{
-		Form_pg_index indexForm = (Form_pg_index) GETSTRUCT(heapTuple);
-		Oid indexId = indexForm->indexrelid;
-		char *statementDef = NULL;
+		Oid constraintId = get_index_constraint(indexId);
+		Assert(constraintId != InvalidOid);
 
-		bool indexImpliedByConstraint = IndexImpliedByAConstraint(indexForm);
-
-		/* get the corresponding constraint or index statement */
-		if (indexImpliedByConstraint)
-		{
-			Oid constraintId = get_index_constraint(indexId);
-			Assert(constraintId != InvalidOid);
-
-			statementDef = pg_get_constraintdef_command(constraintId);
-		}
-		else
-		{
-			statementDef = pg_get_indexdef_string(indexId);
-		}
-
-		/* append found constraint or index definition to the list */
-		indexDDLEventList = lappend(indexDDLEventList, makeTableDDLCommandString(
-										statementDef));
-
-		/* if table is clustered on this index, append definition to the list */
-		if (indexForm->indisclustered)
-		{
-			char *clusteredDef = pg_get_indexclusterdef_string(indexId);
-			Assert(clusteredDef != NULL);
-
-			indexDDLEventList = lappend(indexDDLEventList, makeTableDDLCommandString(
-											clusteredDef));
-		}
-
-		heapTuple = systable_getnext(scanDescriptor);
+		statementDef = pg_get_constraintdef_command(constraintId);
+	}
+	else
+	{
+		statementDef = pg_get_indexdef_string(indexId);
 	}
 
-	/* clean up scan and close system catalog */
-	systable_endscan(scanDescriptor);
-	table_close(pgIndex, AccessShareLock);
+	/* append found constraint or index definition to the list */
+	*indexDDLEventList = lappend(*indexDDLEventList, makeTableDDLCommandString(
+									 statementDef));
 
-	/* revert back to original search_path */
-	PopOverrideSearchPath();
+	/* if table is clustered on this index, append definition to the list */
+	if (indexForm->indisclustered)
+	{
+		char *clusteredDef = pg_get_indexclusterdef_string(indexId);
+		Assert(clusteredDef != NULL);
 
-	return indexDDLEventList;
+		*indexDDLEventList = lappend(*indexDDLEventList, makeTableDDLCommandString(
+										 clusteredDef));
+	}
 }
 
 

src/include/distributed/commands.h

@@ -67,6 +67,8 @@ typedef enum ExtractForeignKeyConstraintsMode
 /* cluster.c - forward declarations */
 extern List * PreprocessClusterStmt(Node *node, const char *clusterCommand);
 
+/* index.c */
+typedef void (*PGIndexProcessor)(Form_pg_index, List **);
 
 /* call.c */
 extern bool CallDistributedProcedureRemotely(CallStmt *callStmt, DestReceiver *dest);
@@ -183,6 +185,8 @@ extern List * PostprocessIndexStmt(Node *node,
 								   const char *queryString);
 extern void ErrorIfUnsupportedAlterIndexStmt(AlterTableStmt *alterTableStatement);
 extern void MarkIndexValid(IndexStmt *indexStmt);
+extern List * ExecuteFunctionOnEachTableIndex(Oid relationId, PGIndexProcessor
+											  pgIndexProcessor);
 
 /* objectaddress.c - forward declarations */
 extern ObjectAddress CreateExtensionStmtObjectAddress(Node *stmt, bool missing_ok);