Re: SELECT with COLLATE results in segfault on trunk and 12 Beta 2

Manuel Rigger <rigger(dot)manuel(at)gmail(dot)com> writes:
> When executing the statements below, Postgres crashes:

> CREATE TABLE t0(c0 BOOLEAN, c1 TEXT);
> CREATE STATISTICS s1 ON c0, c1 FROM t0;
> INSERT INTO t0(c0) VALUES (FALSE);
> VACUUM ANALYZE t0;
> SELECT * FROM t0 WHERE t0.c0 OR '' >= t0.c1 COLLATE "C"; -- unexpected: segfault

Backtrace shows

#0 pg_detoast_datum_packed (datum=0x7f7f7f7f7f7f7f7f) at fmgr.c:1773
#1 0x00000000008a9b90 in text_ge (fcinfo=0x7ffc8cdbfd40) at varlena.c:1859
#2 0x00000000008cf307 in FunctionCall2Coll (flinfo=0x7ffc8cdbfe00,
collation=<value optimized out>, arg1=<value optimized out>,
arg2=<value optimized out>) at fmgr.c:1162
#3 0x0000000000773db0 in mcv_get_match_bitmap (root=0x26b7bc8,
clauses=<value optimized out>, keys=0x26b8b90, mcvlist=0x26b88f0,
is_or=true) at mcv.c:1661
#4 0x0000000000773ecb in mcv_get_match_bitmap (root=0x26b7bc8,
clauses=<value optimized out>, keys=0x26b8b90, mcvlist=0x26b88f0,
is_or=false) at mcv.c:1744
#5 0x0000000000775d61 in mcv_clauselist_selectivity (root=0x26b7bc8,
stat=0x26b8b58, clauses=0x26b9008, varRelid=<value optimized out>,
jointype=<value optimized out>, sjinfo=<value optimized out>,
rel=0x25a46a0, basesel=0x7ffc8cdc0038, totalsel=0x7ffc8cdc0030)
at mcv.c:1876

I think this is another variant of the mcv_get_match_bitmap
issues that you and Andreas already reported, ie, that code isn't
expecting to find anything but a bare Var or Const, so the
CollateExpr node above the Var confuses it.

It's possible that it'd be worth descending through CollateExpr
nodes in the same way as for RelabelType nodes, and for more or
less the same reason.

regards, tom lane