Re: 回复：Re: Re: 回复：Re: Is it worth pushing conditions to sublink/subplan?

On Thu, Dec 23, 2021 at 3:52 AM 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com> wrote:

>
> Fixed a bug found during testing.
>
>
> Wenjing
>
>
>>> Hi,
+ if (condition_is_safe_pushdown_to_sublink(rinfo,
expr_info->outer))
+ {
+ /* replace qual expr from outer var = const to var = const
and push down to sublink query */
+ sublink_query_push_qual(subquery, (Node
*)copyObject(rinfo->clause), expr_info->outer, expr_info->inner);

Since sublink_query_push_qual() is always guarded
by condition_is_safe_pushdown_to_sublink(), it seems
sublink_query_push_qual() can be folded into
condition_is_safe_pushdown_to_sublink().

For generate_base_implied_equalities():

+ if (ec->ec_processed)
+ {
+ ec_index++;
+ continue;
+ }
+ else if (list_length(ec->ec_members) > 1)

Minor comment: the keyword `else` can be omitted (due to `continue` above).

+ * Since there may be an unexpanded sublink in the targetList,
+ * we'll skip it for now.

Since there may be an -> If there is an

+ {"lazy_process_sublink", PGC_USERSET, QUERY_TUNING_METHOD,
+ gettext_noop("enable lazy process sublink."),

Looking at existing examples from src/backend/utils/misc/guc.c,
enable_lazy_sublink_processing seems to be consistent with existing guc
variable naming.

+lazy_process_sublinks(PlannerInfo *root, bool single_result_rte)

lazy_process_sublinks -> lazily_process_sublinks

+ else
+ {
/* There shouldn't be any OJ info to translate, as yet */
Assert(subroot->join_info_list == NIL);

Indentation for the else block is off.

+ if (istop)
+ f->quals = preprocess_expression_ext(root, f->quals,
EXPRKIND_QUAL, false);
+ else
+ f->quals = preprocess_expression_ext(root, f->quals,
EXPRKIND_QUAL, true);

The above can be written as:

+ f->quals = preprocess_expression_ext(root, f->quals,
EXPRKIND_QUAL, !istop);

For find_equal_conditions_contain_uplevelvar_in_sublink_query():
+ context.has_unexpected_expr == false &&
`!context.has_unexpected_expr` should suffice

equal_expr_safety_check -> is_equal_expr_safe

Cheers