Implement table partitioning.

Table partitioning is like table inheritance and reuses much of the
existing infrastructure, but there are some important differences.
The parent is called a partitioned table and is always empty; it may
not have indexes or non-inherited constraints, since those make no
sense for a relation with no data of its own.  The children are called
partitions and contain all of the actual data.  Each partition has an
implicit partitioning constraint.  Multiple inheritance is not
allowed, and partitioning and inheritance can't be mixed.  Partitions
can't have extra columns and may not allow nulls unless the parent
does.  Tuples inserted into the parent are automatically routed to the
correct partition, so tuple-routing ON INSERT triggers are not needed.
Tuple routing isn't yet supported for partitions which are foreign
tables, and it doesn't handle updates that cross partition boundaries.

Currently, tables can be range-partitioned or list-partitioned.  List
partitioning is limited to a single column, but range partitioning can
involve multiple columns.  A partitioning "column" can be an
expression.

Because table partitioning is less general than table inheritance, it
is hoped that it will be easier to reason about properties of
partitions, and therefore that this will serve as a better foundation
for a variety of possible optimizations, including query planner
optimizations.  The tuple routing based which this patch does based on
the implicit partitioning constraints is an example of this, but it
seems likely that many other useful optimizations are also possible.

Amit Langote, reviewed and tested by Robert Haas, Ashutosh Bapat,
Amit Kapila, Rajkumar Raghuwanshi, Corey Huinker, Jaime Casanova,
Rushabh Lathia, Erik Rijkers, among others.  Minor revisions by me.

1 files changed, 15 insertions, 9 deletions

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 85817c65302..eeb2b1fe80d 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -69,8 +69,6 @@ static void ComputeIndexAttrs(IndexInfo *indexInfo,
 				  char *accessMethodName, Oid accessMethodId,
 				  bool amcanorder,
 				  bool isconstraint);
-static Oid GetIndexOpClass(List *opclass, Oid attrType,
-				char *accessMethodName, Oid accessMethodId);
 static char *ChooseIndexName(const char *tabname, Oid namespaceId,
 				List *colnames, List *exclusionOpNames,
 				bool primary, bool isconstraint);
@@ -383,6 +381,11 @@ DefineIndex(Oid relationId,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot create index on foreign table \"%s\"",
 							RelationGetRelationName(rel))));
+		else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("cannot create index on partitioned table \"%s\"",
+							RelationGetRelationName(rel))));
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -1145,10 +1148,10 @@ ComputeIndexAttrs(IndexInfo *indexInfo,
 		/*
 		 * Identify the opclass to use.
 		 */
-		classOidP[attn] = GetIndexOpClass(attribute->opclass,
-										  atttype,
-										  accessMethodName,
-										  accessMethodId);
+		classOidP[attn] = ResolveOpClass(attribute->opclass,
+										 atttype,
+										 accessMethodName,
+										 accessMethodId);
 
 		/*
 		 * Identify the exclusion operator, if any.
@@ -1255,10 +1258,13 @@ ComputeIndexAttrs(IndexInfo *indexInfo,
 
 /*
  * Resolve possibly-defaulted operator class specification
+ *
+ * Note: This is used to resolve operator class specification in index and
+ * partition key definitions.
  */
-static Oid
-GetIndexOpClass(List *opclass, Oid attrType,
-				char *accessMethodName, Oid accessMethodId)
+Oid
+ResolveOpClass(List *opclass, Oid attrType,
+			   char *accessMethodName, Oid accessMethodId)
 {
 	char	   *schemaname;
 	char	   *opcname;