[HACKERS] addRangeTableEntry() relies on pstate, contrary to its documentation
Hi, Since at least 61e532820824504aa92ad93c427722d3fa9c1632 from 2009, addRangeTableEntry() relies pstate being != NULL via its call to isLockedRefname() even though its documentation says: * If pstate is NULL, we just build an RTE and return it without adding it * to an rtable list. I think we should just remove the above sentence and code supporting it from addRangeTableEntry* and add asserts ensuring its passed in. Off list Tom commented that suggestion with: NAK. I'm absolutely certain that there is, or at least once was, code that relied on that feature. Maybe not for addRangeTableEntry itself, but for at least one of its siblings. Yea, there had to be, for the code to be written that way. I'm not exactly an expert in that area of the code, and lots of it predates my involvement in the project... Before removing the feature I'd want to see a trace-down of where that usage went away and an analysis of why the need for it won't come back. Ok. I've only cursorily checked callers. The number of callchains to all of them make it hard to verify it conclusively :( An easy alternative fix, of course, is to not call isLockedRefname if we don't have a pstate (or else put the pstate==NULL test inside it). I'm not a big fan of that - won't that essentially cause the wrong locklevel to be used and thus open the door for lock upgrade deadlocks? Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] addRangeTableEntry() relies on pstate, contrary to its documentation
Andres Freund and...@2ndquadrant.com writes: Off list Tom commented that suggestion with: An easy alternative fix, of course, is to not call isLockedRefname if we don't have a pstate (or else put the pstate==NULL test inside it). I'm not a big fan of that - won't that essentially cause the wrong locklevel to be used and thus open the door for lock upgrade deadlocks? Well, it would amount to assuming that the table was not mentioned in FOR UPDATE. Depending on context, that might be perfectly appropriate. A quick grep finds these places that are visibly passing NULL to one or another addRangeTableEntry* function: convert_ANY_sublink_to_join(): pulls up an ANY subquery with rte = addRangeTableEntryForSubquery(NULL, ... UpdateRangeTableOfViewParse(): inserts NEW/OLD RTEs using rt_entry1 = addRangeTableEntryForRelation(NULL, viewRel, makeAlias(old, NIL), false, false); rt_entry2 = addRangeTableEntryForRelation(NULL, viewRel, makeAlias(new, NIL), false, false); So you would certainly break these callers. I'm not sure whether any of the callers that are passing down their own pstate arguments can ever be passed a NULL; I'm inclined to doubt it though. An alternative of course is to not have this API spec for all addRangeTableEntry* functions, but just the two used this way. I don't much care for that though. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
