The following bug has been logged online:

Bug reference: 1591
Logged by: Michael Williamson
Email address: michael.williamson (AT) caseware (DOT) com
PostgreSQL version: 8.0.1
Operating system: Windows 2000
Description: BETWEEN NULL AND NULL causes crash
Details:

Hello,

I have the following query:

SELECT * FROM Entities
WHERE NULL IS NULL OR (EntityNo BETWEEN NULL AND COALESCE(NULL,NULL))

This causes one of two results: postmaster crashes or goes into an infinite
loop. The reason I have such a strange query is because values are filled
in from a dialog. It looks more like:

SELECT * FROM Entities
WHERE %p1 IS NULL OR (EntityNo BETWEEN %p1 AND COALESCE(%p2,%p1))

This query executes ok on other dbs (mssql, mysql) and returns the correct
result (all records). I can fix it for postgre by doing:

SELECT * FROM Entities
WHERE NULL IS NULL OR (EntityNo BETWEEN NULL AND COALESCE(NULL,NULL,''))

But none the less nothing should make it loop infinitely or crash.

Thanks

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"Michael Williamson" <michael.williamson (AT) caseware (DOT) com> writes:
Good catch. COALESCE(NULL,NULL) is actually broken as far back as 7.4,
though I'm not sure if the error is visible in that version. If you
need the patch it's

Index: clauses.c
================================================== =================
RCS file: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v
retrieving revision 1.186.4.2
diff -c -r1.186.4.2 clauses.c
*** clauses.c 2 Feb 2005 21:49:43 -0000 1.186.4.2
--- clauses.c 10 Apr 2005 20:54:52 -0000
***************
*** 1771,1776 ****
--- 1771,1780 ----
newargs = lappend(newargs, e);
}

+ /* If all the arguments were constant null, the result is just null */
+ if (newargs == NIL)
+ return (Node *) makeNullConst(coalesceexpr->coalescetype);
+
newcoalesce = makeNode(CoalesceExpr);
newcoalesce->coalescetype = coalesceexpr->coalescetype;
newcoalesce->args = newargs;


regards, tom lane

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