Re: crash with sql language partition support function

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: crash with sql language partition support function
Date: 2018-04-12 16:04:46
Message-ID: 20180412160446.l472llhy5v7nhq5o@alvherre.pgsql
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Amit Langote wrote:

> Since this bug also exists in the released PG 10 branch, I also created a
> patch for that. It's slightly different than the one for PG 11dev,
> because there were some changes recently to how the memory context is
> manipulated in RelationBuildPartitionKey. That's
> v1-PG10-0001-Fix-a-memory-context-bug-in-RelationBuildPartitio.patch.

Here's a repro for pg10, which doesn't have hash partitioning:

create function my_int4_sort(int4,int4) returns int language sql
as $$ select case when $1 = $2 then 0 when $1 > $2 then 1 else -1 end; $$;
create operator class test_int4_ops for type int4 using btree as
operator 1 < (int4,int4), operator 2 <= (int4,int4),
operator 3 = (int4,int4), operator 4 >= (int4,int4),
operator 5 > (int4,int4), function 1 my_int4_sort(int4,int4);
create table t (a int4) partition by range (a test_int4_ops);
create table t1 partition of t for values from (0) to (1000);
insert into t values (100);
insert into t values (200); -- *boom*

I'm dealing with this now -- will push shortly. The sane thing to do is
backpatch my previous memcxt fixes, since your patch introduces a
problem that we discussed with that other patch, namely that you would
leak the whole memory context if there is a problem while running the
function. I also noticed here that copy_partition_key is doing memcpy()
on the fmgr_info, which is bogus -- it should be using fmgr_info_copy.
Rather than patching that one piece it seems better to replace it
wholesale, since I bet this won't be the last time we'll hear about this
routine, and I would prefer not to deal with differently broken code in
the older branch.

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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