Eval expression R/O once time (src/backend/executor/execExpr.c)

Ranier Vilela <ranier.vf@gmail.com>

From: Ranier Vilela <ranier.vf@gmail.com>

To: Pg Hackers <pgsql-hackers@postgresql.org>

Date: 2021-09-21T18:09:11Z

Lists: pgsql-hackers

Attachments

fix_eval_expr_once.patch (application/octet-stream) patch

Hi,

Currently when determining where CoerceToDomainValue can be read,
it evaluates every step in a loop.
But, I think that the expression is immutable and should be solved only
once.

Otherwise the logic is wrong since by the rules of C, even though the
variable is
being initialized in the declaration, it still receives initialization at
each repetition.
What causes palloc running multiple times.

In other words:
Datum   *domainval = NULL;

is the same:
Datum   *domainval;
domainval = NULL;

Once there, reduce the scope for save_innermost_domainval and
save_innermost_domainnull.

Thoughts?

regards,
Ranier Vilela

Commits

Fix variable lifespan in ExecInitCoerceToDomain().
- ada667b45496 13.5 landed
- 16a56774fade 14.1 landed
- 01fc6527034a 15.0 landed
expression eval, jit: Minor code cleanups.
- 1ec7679f1b67 13.0 cited
Faster expression evaluation and targetlist projection.
- b8d7f053c5c2 10.0 cited