pgsql: Remove unreachable code in expression evaluation.

Andres Freund <andres@anarazel.de> writes:

Remove unreachable code in expression evaluation.
The previous code still contained expression evaluation time support
for CaseExprs without a defresult. But transformCaseExpr() creates a
default expression if necessary.

BTW, now that I think about it, I wonder if a better answer wouldn't
be to leave the execExpr code as it stood, and remove the code in
transformCaseExpr that pre-creates a default expression. You'd end
up with identical code at runtime, and eliminate some parse/rewrite/plan
overhead for dealing with that subexpression.

It's possible there's some code somewhere else that expects defresult
to always be non-null, but I can't think what, or why that would be
a good thing to assume.

regards, tom lane

--
Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-committers

On 2017-03-26 00:14:30 -0400, Tom Lane wrote:

Andres Freund <andres@anarazel.de> writes:

Remove unreachable code in expression evaluation.
The previous code still contained expression evaluation time support
for CaseExprs without a defresult. But transformCaseExpr() creates a
default expression if necessary.

BTW, now that I think about it, I wonder if a better answer wouldn't
be to leave the execExpr code as it stood, and remove the code in
transformCaseExpr that pre-creates a default expression. You'd end
up with identical code at runtime, and eliminate some parse/rewrite/plan
overhead for dealing with that subexpression.

It's possible there's some code somewhere else that expects defresult
to always be non-null, but I can't think what, or why that would be
a good thing to assume.

There's some relationship with the type inferrence code in
transformCaseExpr(). I don't think it'd be hard to change, however -
just move resultexprs = lcons(newc->defresult, resultexprs); into the
else branch of if defresult == NULL.

- Andres

--
Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-committers