Change SearchSysCache coding conventions so that a reference count is

maintained for each cache entry.  A cache entry will not be freed until
the matching ReleaseSysCache call has been executed.  This eliminates
worries about cache entries getting dropped while still in use.  See
my posting to pg-hackers of even date for more info.

1 files changed, 107 insertions, 88 deletions

diff --git a/src/backend/commands/command.c b/src/backend/commands/command.c
index 958469fa4e1..42f05f0761c 100644
--- a/src/backend/commands/command.c
+++ b/src/backend/commands/command.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.111 2000/11/14 01:57:30 inoue Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.112 2000/11/16 22:30:19 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -274,13 +274,13 @@ AlterTableAddColumn(const char *relationName,
 				attrdesc;
 	Oid			myrelid;
 	HeapTuple	reltup;
+	HeapTuple	newreltup;
 	HeapTuple	attributeTuple;
 	Form_pg_attribute attribute;
 	FormData_pg_attribute attributeD;
 	int			i;
 	int			minattnum,
 				maxatts;
-	HeapTuple	tup;
 	Relation	idescs[Num_pg_attr_indices];
 	Relation	ridescs[Num_pg_class_indices];
 	bool		hasindex;
@@ -359,9 +359,9 @@ AlterTableAddColumn(const char *relationName,
 
 	rel = heap_openr(RelationRelationName, RowExclusiveLock);
 
-	reltup = SearchSysCacheTupleCopy(RELNAME,
-									 PointerGetDatum(relationName),
-									 0, 0, 0);
+	reltup = SearchSysCache(RELNAME,
+							PointerGetDatum(relationName),
+							0, 0, 0);
 
 	if (!HeapTupleIsValid(reltup))
 		elog(ERROR, "ALTER TABLE: relation \"%s\" not found",
@@ -371,10 +371,8 @@ AlterTableAddColumn(const char *relationName,
 	 * XXX is the following check sufficient?
 	 */
 	if (((Form_pg_class) GETSTRUCT(reltup))->relkind != RELKIND_RELATION)
-	{
 		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
 			 relationName);
-	}
 
 	minattnum = ((Form_pg_class) GETSTRUCT(reltup))->relnatts;
 	maxatts = minattnum + 1;
@@ -407,12 +405,10 @@ AlterTableAddColumn(const char *relationName,
 		char	   *typename;
 		int			attnelems;
 
-		tup = SearchSysCacheTuple(ATTNAME,
-								  ObjectIdGetDatum(reltup->t_data->t_oid),
-								  PointerGetDatum(colDef->colname),
-								  0, 0);
-
-		if (HeapTupleIsValid(tup))
+		if (SearchSysCacheExists(ATTNAME,
+								 ObjectIdGetDatum(reltup->t_data->t_oid),
+								 PointerGetDatum(colDef->colname),
+								 0, 0))
 			elog(ERROR, "ALTER TABLE: column name \"%s\" already exists in table \"%s\"",
 				 colDef->colname, relationName);
 
@@ -430,13 +426,13 @@ AlterTableAddColumn(const char *relationName,
 		else
 			attnelems = 0;
 
-		typeTuple = SearchSysCacheTuple(TYPENAME,
-										PointerGetDatum(typename),
-										0, 0, 0);
-		tform = (Form_pg_type) GETSTRUCT(typeTuple);
-
+		typeTuple = SearchSysCache(TYPENAME,
+								   PointerGetDatum(typename),
+								   0, 0, 0);
 		if (!HeapTupleIsValid(typeTuple))
 			elog(ERROR, "ALTER TABLE: type \"%s\" does not exist", typename);
+		tform = (Form_pg_type) GETSTRUCT(typeTuple);
+
 		namestrcpy(&(attribute->attname), colDef->colname);
 		attribute->atttypid = typeTuple->t_data->t_oid;
 		attribute->attlen = tform->typlen;
@@ -453,6 +449,8 @@ AlterTableAddColumn(const char *relationName,
 		attribute->atthasdef = (colDef->raw_default != NULL ||
 								colDef->cooked_default != NULL);
 
+		ReleaseSysCache(typeTuple);
+
 		heap_insert(attrdesc, attributeTuple);
 		if (hasindex)
 			CatalogIndexInsert(idescs,
@@ -466,15 +464,21 @@ AlterTableAddColumn(const char *relationName,
 
 	heap_close(attrdesc, RowExclusiveLock);
 
-	((Form_pg_class) GETSTRUCT(reltup))->relnatts = maxatts;
-	heap_update(rel, &reltup->t_self, reltup, NULL);
+	/*
+	 * Update number of attributes in pg_class tuple
+	 */
+	newreltup = heap_copytuple(reltup);
+
+	((Form_pg_class) GETSTRUCT(newreltup))->relnatts = maxatts;
+	heap_update(rel, &newreltup->t_self, newreltup, NULL);
 
 	/* keep catalog indices current */
 	CatalogOpenIndices(Num_pg_class_indices, Name_pg_class_indices, ridescs);
-	CatalogIndexInsert(ridescs, Num_pg_class_indices, rel, reltup);
+	CatalogIndexInsert(ridescs, Num_pg_class_indices, rel, newreltup);
 	CatalogCloseIndices(Num_pg_class_indices, ridescs);
 
-	heap_freetuple(reltup);
+	heap_freetuple(newreltup);
+	ReleaseSysCache(reltup);
 
 	heap_close(rel, NoLock);
 
@@ -555,11 +559,10 @@ AlterTableAlterColumn(const char *relationName,
 	/*
 	 * get the number of the attribute
 	 */
-	tuple = SearchSysCacheTuple(ATTNAME,
-								ObjectIdGetDatum(myrelid),
-								PointerGetDatum(colName),
-								0, 0);
-
+	tuple = SearchSysCache(ATTNAME,
+						   ObjectIdGetDatum(myrelid),
+						   PointerGetDatum(colName),
+						   0, 0);
 	if (!HeapTupleIsValid(tuple))
 	{
 		heap_close(rel, AccessExclusiveLock);
@@ -568,6 +571,7 @@ AlterTableAlterColumn(const char *relationName,
 	}
 
 	attnum = ((Form_pg_attribute) GETSTRUCT(tuple))->attnum;
+	ReleaseSysCache(tuple);
 
 	if (newDefault)				/* SET DEFAULT */
 	{
@@ -595,7 +599,6 @@ AlterTableAlterColumn(const char *relationName,
 		Relation	attr_rel;
 		ScanKeyData scankeys[3];
 		HeapScanDesc scan;
-		HeapTuple	tuple;
 
 		attr_rel = heap_openr(AttributeRelationName, AccessExclusiveLock);
 		ScanKeyEntryInitialize(&scankeys[0], 0x0,
@@ -867,10 +870,11 @@ RemoveColumnReferences(Oid reloid, int attnum, bool checkonly, HeapTuple reltup)
 				}
 				else
 				{
-					htup = SearchSysCacheTuple(RELOID,
-									 ObjectIdGetDatum(index->indexrelid),
-											   0, 0, 0);
+					htup = SearchSysCache(RELOID,
+										  ObjectIdGetDatum(index->indexrelid),
+										  0, 0, 0);
 					RemoveIndex(NameStr(((Form_pg_class) GETSTRUCT(htup))->relname));
+					ReleaseSysCache(htup);
 				}
 				break;
 			}
@@ -941,18 +945,19 @@ AlterTableDropColumn(const char *relationName,
 	if (length(find_all_inheritors(myrelid)) > 1)
 		elog(ERROR, "ALTER TABLE: cannot drop a column on table that is inherited from");
 
-
 	/*
 	 * lock the pg_class tuple for update
 	 */
-	reltup = SearchSysCacheTuple(RELNAME, PointerGetDatum(relationName),
-								 0, 0, 0);
-
+	rel = heap_openr(RelationRelationName, RowExclusiveLock);
+	reltup = SearchSysCache(RELNAME,
+							PointerGetDatum(relationName),
+							0, 0, 0);
 	if (!HeapTupleIsValid(reltup))
 		elog(ERROR, "ALTER TABLE: relation \"%s\" not found",
 			 relationName);
-	rel = heap_openr(RelationRelationName, RowExclusiveLock);
 	classtuple.t_self = reltup->t_self;
+	ReleaseSysCache(reltup);
+
 	switch (heap_mark4update(rel, &classtuple, &buffer))
 	{
 		case HeapTupleSelfUpdated:
@@ -976,19 +981,21 @@ AlterTableDropColumn(const char *relationName,
 	attrdesc = heap_openr(AttributeRelationName, RowExclusiveLock);
 
 	/*
-	 * Get the target pg_attribute tuple
+	 * Get the target pg_attribute tuple and make a modifiable copy
 	 */
-	tup = SearchSysCacheTupleCopy(ATTNAME,
-								  ObjectIdGetDatum(reltup->t_data->t_oid),
-								  PointerGetDatum(colName), 0, 0);
+	tup = SearchSysCacheCopy(ATTNAME,
+							 ObjectIdGetDatum(reltup->t_data->t_oid),
+							 PointerGetDatum(colName),
+							 0, 0);
 	if (!HeapTupleIsValid(tup))
 		elog(ERROR, "ALTER TABLE: column name \"%s\" doesn't exist in table \"%s\"",
 			 colName, relationName);
 
 	attribute = (Form_pg_attribute) GETSTRUCT(tup);
-	if (attribute->attnum <= 0)
-		elog(ERROR, "ALTER TABLE: column name \"%s\" was already dropped", colName);
 	attnum = attribute->attnum;
+	if (attnum <= 0)
+		elog(ERROR, "ALTER TABLE: column name \"%s\" was already dropped",
+			 colName);
 	attoid = tup->t_data->t_oid;
 
 	/*
@@ -1226,10 +1233,9 @@ AlterTableAddConstraint(char *relationName,
 			int			count;
 			List       *indexoidlist,
 				*indexoidscan;
-			Form_pg_index indexStruct = NULL;
 			Form_pg_attribute *rel_attrs = NULL;
-			int                     i;
-			int found=0;
+			int			i;
+			bool		found = false;
 
 			if (get_temp_rel_by_username(fkconstraint->pktable_name)!=NULL &&
 				get_temp_rel_by_username(relationName)==NULL) {
@@ -1264,42 +1270,50 @@ AlterTableAddConstraint(char *relationName,
 			indexoidlist = RelationGetIndexList(pkrel);
 
 			foreach(indexoidscan, indexoidlist)
+			{
+				Oid             indexoid = lfirsti(indexoidscan);
+				HeapTuple       indexTuple;
+				Form_pg_index	indexStruct;
+
+				indexTuple = SearchSysCache(INDEXRELID,
+											ObjectIdGetDatum(indexoid),
+											0, 0, 0);
+				if (!HeapTupleIsValid(indexTuple))
+					elog(ERROR, "transformFkeyGetPrimaryKey: index %u not found",
+						 indexoid);
+				indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
+
+				if (indexStruct->indisunique)
 				{
-					Oid             indexoid = lfirsti(indexoidscan);
-					HeapTuple       indexTuple;
-					List *attrl;
-					indexTuple = SearchSysCacheTuple(INDEXRELID,
-													 ObjectIdGetDatum(indexoid),
-													 0, 0, 0);
-					if (!HeapTupleIsValid(indexTuple))
-						elog(ERROR, "transformFkeyGetPrimaryKey: index %u not found",
-							 indexoid);
-					indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
-
-					if (indexStruct->indisunique) {
-						/* go through the fkconstraint->pk_attrs list */
-						foreach(attrl, fkconstraint->pk_attrs) {
-							Ident *attr=lfirst(attrl);
-							found=0;
-							for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0; i++)
+					List	   *attrl;
+
+					/* go through the fkconstraint->pk_attrs list */
+					foreach(attrl, fkconstraint->pk_attrs)
+					{
+						Ident *attr=lfirst(attrl);
+						found = false;
+						for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0; i++)
+						{
+							int pkattno = indexStruct->indkey[i];
+							if (pkattno>0)
 							{
-								int pkattno = indexStruct->indkey[i];
-								if (pkattno>0) {
-									char *name = NameStr(rel_attrs[pkattno-1]->attname);
-									if (strcmp(name, attr->name)==0) {
-										found=1;
-										break;
-									}
+								char *name = NameStr(rel_attrs[pkattno-1]->attname);
+								if (strcmp(name, attr->name)==0)
+								{
+									found = true;
+									break;
 								}
 							}
-							if (!found)
-								break;
 						}
+						if (!found)
+							break;
 					}
-					if (found)
-						break;
-					indexStruct = NULL;
 				}
+				ReleaseSysCache(indexTuple);
+				if (found)
+					break;
+			}
+
 			if (!found)
 				elog(ERROR, "UNIQUE constraint matching given keys for referenced table \"%s\" not found",
 					 fkconstraint->pktable_name);
@@ -1309,17 +1323,18 @@ AlterTableAddConstraint(char *relationName,
 
 			rel_attrs = rel->rd_att->attrs;
 			if (fkconstraint->fk_attrs!=NIL) {
-				int found=0;
 				List *fkattrs;
 				Ident *fkattr;
+
+				found = false;
 				foreach(fkattrs, fkconstraint->fk_attrs) {
-					int count=0;
-					found=0;
+					int count;
+					found = false;
 					fkattr=lfirst(fkattrs);
-					for (; count < rel->rd_att->natts; count++) {
+					for (count = 0; count < rel->rd_att->natts; count++) {
 						char *name = NameStr(rel->rd_att->attrs[count]->attname);
 						if (strcmp(name, fkattr->name)==0) {
-							found=1;
+							found = true;
 							break;
 						}
 					}
@@ -1441,20 +1456,22 @@ AlterTableOwner(const char *relationName, const char *newOwnerName)
 	/*
 	 * look up the new owner in pg_shadow and get the sysid
 	 */
-	tuple = SearchSysCacheTuple(SHADOWNAME, PointerGetDatum(newOwnerName),
-								0, 0, 0);
+	tuple = SearchSysCache(SHADOWNAME,
+						   PointerGetDatum(newOwnerName),
+						   0, 0, 0);
 	if (!HeapTupleIsValid(tuple))
 		elog(ERROR, "ALTER TABLE: user \"%s\" not found", newOwnerName);
-
 	newOwnerSysid = ((Form_pg_shadow) GETSTRUCT(tuple))->usesysid;
+	ReleaseSysCache(tuple);
 
 	/*
-	 * find the table's entry in pg_class and lock it for writing
+	 * find the table's entry in pg_class and make a modifiable copy
 	 */
 	class_rel = heap_openr(RelationRelationName, RowExclusiveLock);
 
-	tuple = SearchSysCacheTupleCopy(RELNAME, PointerGetDatum(relationName),
-								 0, 0, 0);
+	tuple = SearchSysCacheCopy(RELNAME,
+							   PointerGetDatum(relationName),
+							   0, 0, 0);
 	if (!HeapTupleIsValid(tuple))
 		elog(ERROR, "ALTER TABLE: relation \"%s\" not found",
 			 relationName);
@@ -1525,13 +1542,15 @@ AlterTableCreateToastTable(const char *relationName, bool silent)
 	 */
 	class_rel = heap_openr(RelationRelationName, RowExclusiveLock);
 
-	reltup = SearchSysCacheTuple(RELNAME, PointerGetDatum(relationName),
-								 0, 0, 0);
+	reltup = SearchSysCache(RELNAME,
+							PointerGetDatum(relationName),
+							0, 0, 0);
 	if (!HeapTupleIsValid(reltup))
 		elog(ERROR, "ALTER TABLE: relation \"%s\" not found",
 			 relationName);
-
 	classtuple.t_self = reltup->t_self;
+	ReleaseSysCache(reltup);
+
 	switch (heap_mark4update(class_rel, &classtuple, &buffer))
 	{
 		case HeapTupleSelfUpdated: