BUG #14344: string_agg(DISTINCT ..) crash

The following bug has been logged on the website:

Bug reference: 14344
Logged by: Regina Obe
Email address: lr(at)pcorp(dot)us
PostgreSQL version: 9.6rc1
Operating system: Windows 2012 and Windows 7 64-bit
Description:

Let me know if you need more info or if this has already been fixed.

I was testing under

PostgreSQL 9.6rc1, compiled by Visual C++ build 1800, 64-bit

And was able to trigger a crash with this:

-- create test table
CREATE TABLE string_agg_crash_test AS
SELECT i AS id, states[mod(i,6) + 1] AS state, 'junk' || chr(mod(i, 26) + 1)
AS junk
FROM generate_series(1,100000) AS i, (SELECT
'{NULL,MA,HI,IL,KS,NY,NJ}'::varchar[] AS states) AS s ;

-- try to summarize crashes with parallel or not
-- so doesn't seem to be parallel worker related.

set max_parallel_workers_per_gather = 0;
SELECT string_agg(DISTINCT state, ',' ORDER BY state)
FROM string_agg_crash_test;

-- it must have something to do with the DISTINCT, because
-- this doesn't crash
set max_parallel_workers_per_gather = 0;
SELECT string_agg(state, ',' ORDER BY state)
FROM string_agg_crash_test;

The logs don't give me any useful info just

WARNING: terminating connection because of crash of another server
process