From 28bb8c496691e0fb60f49eac08b4dc1d8bdd6b4a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 1 Dec 2020 14:02:28 -0500 Subject: Ensure that expandTableLikeClause() re-examines the same table. As it stood, expandTableLikeClause() re-did the same relation_openrv call that transformTableLikeClause() had done. However there are scenarios where this would not find the same table as expected. We hold lock on the LIKE source table, so it can't be renamed or dropped, but another table could appear before it in the search path. This explains the odd behavior reported in bug #16758 when cloning a table as a temp table of the same name. This case worked as expected before commit 502898192 introduced the need to open the source table twice, so we should fix it. To make really sure we get the same table, let's re-open it by OID not name. That requires adding an OID field to struct TableLikeClause, which is a little nervous-making from an ABI standpoint, but as long as it's at the end I don't think there's any serious risk. Per bug #16758 from Marc Boeren. Like the previous patch, back-patch to all supported branches. Discussion: https://postgr.es/m/16758-840e84a6cfab276d@postgresql.org --- src/backend/parser/parse_utilcmd.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'src/backend/parser/parse_utilcmd.c') diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c index 51180c435a8..9b4874dc11d 100644 --- a/src/backend/parser/parse_utilcmd.c +++ b/src/backend/parser/parse_utilcmd.c @@ -1100,12 +1100,16 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla * yet know what column numbers the copied columns will have in the * finished table. If any of those options are specified, add the LIKE * clause to cxt->likeclauses so that expandTableLikeClause will be called - * after we do know that. + * after we do know that. Also, remember the relation OID so that + * expandTableLikeClause is certain to open the same table. */ if (table_like_clause->options & (CREATE_TABLE_LIKE_CONSTRAINTS | CREATE_TABLE_LIKE_INDEXES)) + { + table_like_clause->relationOid = RelationGetRelid(relation); cxt->likeclauses = lappend(cxt->likeclauses, table_like_clause); + } /* * We may copy extended statistics if requested, since the representation @@ -1177,9 +1181,13 @@ expandTableLikeClause(RangeVar *heapRel, TableLikeClause *table_like_clause) * Open the relation referenced by the LIKE clause. We should still have * the table lock obtained by transformTableLikeClause (and this'll throw * an assertion failure if not). Hence, no need to recheck privileges - * etc. + * etc. We must open the rel by OID not name, to be sure we get the same + * table. */ - relation = relation_openrv(table_like_clause->relation, NoLock); + if (!OidIsValid(table_like_clause->relationOid)) + elog(ERROR, "expandTableLikeClause called on untransformed LIKE clause"); + + relation = relation_open(table_like_clause->relationOid, NoLock); tupleDesc = RelationGetDescr(relation); constr = tupleDesc->constr; -- cgit v1.2.3