Re: [SQL] Problem with limit / union / etc.

"M. Scott Smith" <mssmit1(at)afterlife(dot)ncsc(dot)mil> writes:
> What I want to do is pull out upcoming events, limiting the number
> returned. The following query is my attempt to do that. The
> first select selects all events that have a URL associated with
> them; the second query selects all events that DON'T have a URL
> associated with them; the results are combined together. My
> hope is that the order by/limit clause will limit the results returned
> after they are combined, but it seems to be ignoring this.

Yeah, there's a bug in 6.5.* that causes it to ignore LIMIT on a UNION.
I fixed it a couple months ago, but there's been no new release since
then. Here's the patch, if you want to patch your copy:

*** src/backend/rewrite/rewriteHandler.c~ Sun Jul 11 13:54:30 1999
--- src/backend/rewrite/rewriteHandler.c Tue Oct 19 00:38:05 1999
***************
*** 2859,2864 ****
--- 2859,2866 ----
bool isBinary,
isPortal,
isTemp;
+ Node *limitOffset,
+ *limitCount;
CmdType commandType = CMD_SELECT;
List *rtable_insert = NIL;

***************
*** 2909,2914 ****
--- 2911,2918 ----
isBinary = parsetree->isBinary;
isPortal = parsetree->isPortal;
isTemp = parsetree->isTemp;
+ limitOffset = parsetree->limitOffset;
+ limitCount = parsetree->limitCount;

/*
* The operator tree attached to parsetree->intersectClause is still
***************
*** 3094,3099 ****
--- 3098,3105 ----
result->isPortal = isPortal;
result->isBinary = isBinary;
result->isTemp = isTemp;
+ result->limitOffset = limitOffset;
+ result->limitCount = limitCount;

/*
* The relation to insert into is attached to the range table of the

regards, tom lane