From 8e5aa491ee6754d55001f568557454fcfd65eb41 Mon Sep 17 00:00:00 2001 From: Yugo Nagata Date: Mon, 31 Mar 2025 20:17:07 +0900 Subject: [PATCH v5 2/3] Prevent internal error caused by concurrent ALTER FUNCTION Previously, concurrent ALTER FUNCTION commands could fail with an internal error "tuple concurrently updated". This occurred because multiple sessions attempted to modify the same catalog tuple simultaneously. To prevent this, ensure that an exclusive lock on the function object is acquired earlier in the process. Additionally, if the target function is dropped by another session while waiting for the lock, an appropriate error is raised to indicate the object no longer exists. --- src/backend/commands/functioncmds.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c index 0335e982b31..5bb03153c0d 100644 --- a/src/backend/commands/functioncmds.c +++ b/src/backend/commands/functioncmds.c @@ -61,6 +61,7 @@ #include "parser/parse_func.h" #include "parser/parse_type.h" #include "pgstat.h" +#include "storage/lmgr.h" #include "tcop/pquery.h" #include "tcop/utility.h" #include "utils/acl.h" @@ -1383,9 +1384,21 @@ AlterFunction(ParseState *pstate, AlterFunctionStmt *stmt) ObjectAddressSet(address, ProcedureRelationId, funcOid); + /* Lock the function so nobody else can do anything with it. */ + LockDatabaseObject(ProcedureRelationId, funcOid, 0, AccessExclusiveLock); + + /* + * It is possible that by the time we acquire the lock on function, + * concurrent DDL has removed it. We can test this by checking the + * existence of function. We get the tuple again to avoid the risk + * of function definition getting changed. + */ tup = SearchSysCacheCopy1(PROCOID, ObjectIdGetDatum(funcOid)); - if (!HeapTupleIsValid(tup)) /* should not happen */ - elog(ERROR, "cache lookup failed for function %u", funcOid); + if (!HeapTupleIsValid(tup)) + ereport(ERROR, + errcode(ERRCODE_UNDEFINED_OBJECT), + errmsg("function \"%s\" does not exist", + NameListToString(stmt->func->objname))); procForm = (Form_pg_proc) GETSTRUCT(tup); -- 2.43.0