Re: ERROR: found unexpected null value in index

On Tue, Jul 9, 2019 at 4:52 PM Manuel Rigger <rigger(dot)manuel(at)gmail(dot)com> wrote:
> CREATE TABLE t0(c0 TEXT);
> INSERT INTO t0(c0) VALUES('b'), ('a');
> ANALYZE;
> INSERT INTO t0(c0) VALUES (NULL);
> UPDATE t0 SET c0 = 'a';
> CREATE INDEX i0 ON t0(c0);
> SELECT * FROM t0 WHERE 'baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
> > t0.c0; -- unexpected: ERROR: found unexpected null value in index
> "i0"
>
> The SELECT can result in "ERROR: found unexpected null value in index
> "i0"". I could reproduce this error only when some actions on other
> databases are performed. The error is rather difficult to reproduce,
> and small changes to the above statements cause it to no longer be
> reproducible on my machine.

The error comes from a point at which the planner accesses the index
before execution proper, within get_actual_variable_range(). Perhaps
commit 3ca930fc39c is to blame.

--
Peter Geoghegan