Dmitry Koterov <dmitry.kote...@gmail.com> writes:
> PG13+. Assume we have two identical queries with no arguments (as a plain
> text, e.g. passed to PQexec - NOT to PQexecParams!):
> - one with "a=X AND b IN(...)"
> - and one with "a=X and b=ANY('{...}')
> The question: is it guaranteed that the planner will always choose
> identical plans for them (or, at least, the plan for ANY will not match an
> existing index worse than the plan with IN)?
This depends greatly on what "..." represents. But if it's a list
of constants, they're probably equivalent. transformAExprIn()
offers some caveats:
* We try to generate a ScalarArrayOpExpr from IN/NOT IN, but this is only
* possible if there is a suitable array type available. If not, we fall
* back to a boolean condition tree with multiple copies of the lefthand
* expression. Also, any IN-list items that contain Vars are handled as
* separate boolean conditions, because that gives the planner more scope
* for optimization on such clauses.
regards, tom lane
