Move pg_attrdef manipulation code into new file catalog/pg_attrdef.c.

This is a pure refactoring commit: there isn't (I hope) any functional
change.

StoreAttrDefault and RemoveAttrDefault[ById] are moved from heap.c,
reducing the size of that overly-large file by about 300 lines.
I took the opportunity to trim unused #includes from heap.c, too.

Two new functions for translating between a pg_attrdef OID and the
relid/attnum of the owning column are created by extracting ad-hoc
code from objectaddress.c.  This already removes one copy of said
code, and a follow-on bug fix will create more callers.

The only other function directly manipulating pg_attrdef is
AttrDefaultFetch.  I judged it was better to leave that in relcache.c,
since it shares special concerns about recursion and error handling
with the rest of that module.

Discussion: https://postgr.es/m/651168.1647451676@sss.pgh.pa.us

Author: tglsfdc

src/backend/catalog/Makefile

@@ -25,6 +25,7 @@ OBJS = \
 	objectaddress.o \
 	partition.o \
 	pg_aggregate.o \
+	pg_attrdef.o \
 	pg_cast.o \
 	pg_class.o \
 	pg_collation.o \

src/backend/catalog/heap.c

@@ -30,19 +30,11 @@
 #include "postgres.h"
 
 #include "access/genam.h"
-#include "access/htup_details.h"
 #include "access/multixact.h"
 #include "access/relation.h"
-#include "access/sysattr.h"
 #include "access/table.h"
 #include "access/tableam.h"
-#include "access/toast_compression.h"
-#include "access/transam.h"
-#include "access/xact.h"
-#include "access/xlog.h"
-#include "catalog/binary_upgrade.h"
 #include "catalog/catalog.h"
-#include "catalog/dependency.h"
 #include "catalog/heap.h"
 #include "catalog/index.h"
 #include "catalog/objectaccess.h"
@@ -61,10 +53,8 @@
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_type.h"
 #include "catalog/storage.h"
-#include "catalog/storage_xlog.h"
 #include "commands/tablecmds.h"
 #include "commands/typecmds.h"
-#include "executor/executor.h"
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/optimizer.h"
@@ -76,16 +66,10 @@
 #include "partitioning/partdesc.h"
 #include "storage/lmgr.h"
 #include "storage/predicate.h"
-#include "storage/smgr.h"
-#include "utils/acl.h"
 #include "utils/builtins.h"
-#include "utils/datum.h"
 #include "utils/fmgroids.h"
 #include "utils/inval.h"
 #include "utils/lsyscache.h"
-#include "utils/partcache.h"
-#include "utils/ruleutils.h"
-#include "utils/snapmgr.h"
 #include "utils/syscache.h"
 
 
@@ -1757,131 +1741,6 @@ RemoveAttributeById(Oid relid, AttrNumber attnum)
 	relation_close(rel, NoLock);
 }
 
-/*
- *		RemoveAttrDefault
- *
- * If the specified relation/attribute has a default, remove it.
- * (If no default, raise error if complain is true, else return quietly.)
- */
-void
-RemoveAttrDefault(Oid relid, AttrNumber attnum,
-				  DropBehavior behavior, bool complain, bool internal)
-{
-	Relation	attrdef_rel;
-	ScanKeyData scankeys[2];
-	SysScanDesc scan;
-	HeapTuple	tuple;
-	bool		found = false;
-
-	attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
-
-	ScanKeyInit(&scankeys[0],
-				Anum_pg_attrdef_adrelid,
-				BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(relid));
-	ScanKeyInit(&scankeys[1],
-				Anum_pg_attrdef_adnum,
-				BTEqualStrategyNumber, F_INT2EQ,
-				Int16GetDatum(attnum));
-
-	scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true,
-							  NULL, 2, scankeys);
-
-	/* There should be at most one matching tuple, but we loop anyway */
-	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
-	{
-		ObjectAddress object;
-		Form_pg_attrdef attrtuple = (Form_pg_attrdef) GETSTRUCT(tuple);
-
-		object.classId = AttrDefaultRelationId;
-		object.objectId = attrtuple->oid;
-		object.objectSubId = 0;
-
-		performDeletion(&object, behavior,
-						internal ? PERFORM_DELETION_INTERNAL : 0);
-
-		found = true;
-	}
-
-	systable_endscan(scan);
-	table_close(attrdef_rel, RowExclusiveLock);
-
-	if (complain && !found)
-		elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
-			 relid, attnum);
-}
-
-/*
- *		RemoveAttrDefaultById
- *
- * Remove a pg_attrdef entry specified by OID.  This is the guts of
- * attribute-default removal.  Note it should be called via performDeletion,
- * not directly.
- */
-void
-RemoveAttrDefaultById(Oid attrdefId)
-{
-	Relation	attrdef_rel;
-	Relation	attr_rel;
-	Relation	myrel;
-	ScanKeyData scankeys[1];
-	SysScanDesc scan;
-	HeapTuple	tuple;
-	Oid			myrelid;
-	AttrNumber	myattnum;
-
-	/* Grab an appropriate lock on the pg_attrdef relation */
-	attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
-
-	/* Find the pg_attrdef tuple */
-	ScanKeyInit(&scankeys[0],
-				Anum_pg_attrdef_oid,
-				BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(attrdefId));
-
-	scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
-							  NULL, 1, scankeys);
-
-	tuple = systable_getnext(scan);
-	if (!HeapTupleIsValid(tuple))
-		elog(ERROR, "could not find tuple for attrdef %u", attrdefId);
-
-	myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
-	myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;
-
-	/* Get an exclusive lock on the relation owning the attribute */
-	myrel = relation_open(myrelid, AccessExclusiveLock);
-
-	/* Now we can delete the pg_attrdef row */
-	CatalogTupleDelete(attrdef_rel, &tuple->t_self);
-
-	systable_endscan(scan);
-	table_close(attrdef_rel, RowExclusiveLock);
-
-	/* Fix the pg_attribute row */
-	attr_rel = table_open(AttributeRelationId, RowExclusiveLock);
-
-	tuple = SearchSysCacheCopy2(ATTNUM,
-								ObjectIdGetDatum(myrelid),
-								Int16GetDatum(myattnum));
-	if (!HeapTupleIsValid(tuple))	/* shouldn't happen */
-		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
-			 myattnum, myrelid);
-
-	((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;
-
-	CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
-
-	/*
-	 * Our update of the pg_attribute row will force a relcache rebuild, so
-	 * there's nothing else to do here.
-	 */
-	table_close(attr_rel, RowExclusiveLock);
-
-	/* Keep lock on attribute's rel until end of xact */
-	relation_close(myrel, NoLock);
-}
-
 /*
  * heap_drop_with_catalog	- removes specified relation from catalogs
  *
@@ -2193,195 +2052,6 @@ SetAttrMissing(Oid relid, char *attname, char *value)
 	table_close(tablerel, AccessExclusiveLock);
 }
 
-/*
- * Store a default expression for column attnum of relation rel.
- *
- * Returns the OID of the new pg_attrdef tuple.
- *
- * add_column_mode must be true if we are storing the default for a new
- * attribute, and false if it's for an already existing attribute. The reason
- * for this is that the missing value must never be updated after it is set,
- * which can only be when a column is added to the table. Otherwise we would
- * in effect be changing existing tuples.
- */
-Oid
-StoreAttrDefault(Relation rel, AttrNumber attnum,
-				 Node *expr, bool is_internal, bool add_column_mode)
-{
-	char	   *adbin;
-	Relation	adrel;
-	HeapTuple	tuple;
-	Datum		values[4];
-	static bool nulls[4] = {false, false, false, false};
-	Relation	attrrel;
-	HeapTuple	atttup;
-	Form_pg_attribute attStruct;
-	char		attgenerated;
-	Oid			attrdefOid;
-	ObjectAddress colobject,
-				defobject;
-
-	adrel = table_open(AttrDefaultRelationId, RowExclusiveLock);
-
-	/*
-	 * Flatten expression to string form for storage.
-	 */
-	adbin = nodeToString(expr);
-
-	/*
-	 * Make the pg_attrdef entry.
-	 */
-	attrdefOid = GetNewOidWithIndex(adrel, AttrDefaultOidIndexId,
-									Anum_pg_attrdef_oid);
-	values[Anum_pg_attrdef_oid - 1] = ObjectIdGetDatum(attrdefOid);
-	values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel);
-	values[Anum_pg_attrdef_adnum - 1] = attnum;
-	values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin);
-
-	tuple = heap_form_tuple(adrel->rd_att, values, nulls);
-	CatalogTupleInsert(adrel, tuple);
-
-	defobject.classId = AttrDefaultRelationId;
-	defobject.objectId = attrdefOid;
-	defobject.objectSubId = 0;
-
-	table_close(adrel, RowExclusiveLock);
-
-	/* now can free some of the stuff allocated above */
-	pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
-	heap_freetuple(tuple);
-	pfree(adbin);
-
-	/*
-	 * Update the pg_attribute entry for the column to show that a default
-	 * exists.
-	 */
-	attrrel = table_open(AttributeRelationId, RowExclusiveLock);
-	atttup = SearchSysCacheCopy2(ATTNUM,
-								 ObjectIdGetDatum(RelationGetRelid(rel)),
-								 Int16GetDatum(attnum));
-	if (!HeapTupleIsValid(atttup))
-		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
-			 attnum, RelationGetRelid(rel));
-	attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
-	attgenerated = attStruct->attgenerated;
-	if (!attStruct->atthasdef)
-	{
-		Form_pg_attribute defAttStruct;
-
-		ExprState  *exprState;
-		Expr	   *expr2 = (Expr *) expr;
-		EState	   *estate = NULL;
-		ExprContext *econtext;
-		Datum		valuesAtt[Natts_pg_attribute];
-		bool		nullsAtt[Natts_pg_attribute];
-		bool		replacesAtt[Natts_pg_attribute];
-		Datum		missingval = (Datum) 0;
-		bool		missingIsNull = true;
-
-		MemSet(valuesAtt, 0, sizeof(valuesAtt));
-		MemSet(nullsAtt, false, sizeof(nullsAtt));
-		MemSet(replacesAtt, false, sizeof(replacesAtt));
-		valuesAtt[Anum_pg_attribute_atthasdef - 1] = true;
-		replacesAtt[Anum_pg_attribute_atthasdef - 1] = true;
-
-		if (rel->rd_rel->relkind == RELKIND_RELATION && add_column_mode &&
-			!attgenerated)
-		{
-			expr2 = expression_planner(expr2);
-			estate = CreateExecutorState();
-			exprState = ExecPrepareExpr(expr2, estate);
-			econtext = GetPerTupleExprContext(estate);
-
-			missingval = ExecEvalExpr(exprState, econtext,
-									  &missingIsNull);
-
-			FreeExecutorState(estate);
-
-			defAttStruct = TupleDescAttr(rel->rd_att, attnum - 1);
-
-			if (missingIsNull)
-			{
-				/* if the default evaluates to NULL, just store a NULL array */
-				missingval = (Datum) 0;
-			}
-			else
-			{
-				/* otherwise make a one-element array of the value */
-				missingval = PointerGetDatum(construct_array(&missingval,
-															 1,
-															 defAttStruct->atttypid,
-															 defAttStruct->attlen,
-															 defAttStruct->attbyval,
-															 defAttStruct->attalign));
-			}
-
-			valuesAtt[Anum_pg_attribute_atthasmissing - 1] = !missingIsNull;
-			replacesAtt[Anum_pg_attribute_atthasmissing - 1] = true;
-			valuesAtt[Anum_pg_attribute_attmissingval - 1] = missingval;
-			replacesAtt[Anum_pg_attribute_attmissingval - 1] = true;
-			nullsAtt[Anum_pg_attribute_attmissingval - 1] = missingIsNull;
-		}
-		atttup = heap_modify_tuple(atttup, RelationGetDescr(attrrel),
-								   valuesAtt, nullsAtt, replacesAtt);
-
-		CatalogTupleUpdate(attrrel, &atttup->t_self, atttup);
-
-		if (!missingIsNull)
-			pfree(DatumGetPointer(missingval));
-
-	}
-	table_close(attrrel, RowExclusiveLock);
-	heap_freetuple(atttup);
-
-	/*
-	 * Make a dependency so that the pg_attrdef entry goes away if the column
-	 * (or whole table) is deleted.
-	 */
-	colobject.classId = RelationRelationId;
-	colobject.objectId = RelationGetRelid(rel);
-	colobject.objectSubId = attnum;
-
-	recordDependencyOn(&defobject, &colobject, DEPENDENCY_AUTO);
-
-	/*
-	 * Record dependencies on objects used in the expression, too.
-	 */
-	if (attgenerated)
-	{
-		/*
-		 * Generated column: Dropping anything that the generation expression
-		 * refers to automatically drops the generated column.
-		 */
-		recordDependencyOnSingleRelExpr(&colobject, expr, RelationGetRelid(rel),
-										DEPENDENCY_AUTO,
-										DEPENDENCY_AUTO, false);
-	}
-	else
-	{
-		/*
-		 * Normal default: Dropping anything that the default refers to
-		 * requires CASCADE and drops the default only.
-		 */
-		recordDependencyOnSingleRelExpr(&defobject, expr, RelationGetRelid(rel),
-										DEPENDENCY_NORMAL,
-										DEPENDENCY_NORMAL, false);
-	}
-
-	/*
-	 * Post creation hook for attribute defaults.
-	 *
-	 * XXX. ALTER TABLE ALTER COLUMN SET/DROP DEFAULT is implemented with a
-	 * couple of deletion/creation of the attribute's default entry, so the
-	 * callee should check existence of an older version of this entry if it
-	 * needs to distinguish.
-	 */
-	InvokeObjectPostCreateHookArg(AttrDefaultRelationId,
-								  RelationGetRelid(rel), attnum, is_internal);
-
-	return attrdefOid;
-}
-
 /*
  * Store a check-constraint expression for the given relation.
  *