Hi:
The following snippet is cited from version 15.14, function
check_outerjoin_delay()
2055: /* yes; have we included all its rels in relids? */
2056: if (!bms_is_subset(sjinfo->min_lefthand,
relids) ||
2057: !bms_is_subset(sjinfo->min_righthand,
relids))
2058: {
2059: /* no, so add them in */
2060: relids = bms_add_members(relids,
sjinfo->min_lefthand);
2061: relids = bms_add_members(relids,
sjinfo->min_righthand);
2062: outerjoin_delayed = true;
2063: /* we'll need another iteration */
2064: found_some = true;
2065: }
2066: /* track all the nullable rels of relevant OJs */
2067: nullable_relids = bms_add_members(nullable_relids,
2068:
sjinfo->min_righthand);
2069: if (sjinfo->jointype == JOIN_FULL)
2070: nullable_relids =
bms_add_members(nullable_relids,
2071:
sjinfo->min_lefthand);
2072: /* set delay_upper_joins if needed */
2073: if (is_pushed_down && sjinfo->jointype
!= JOIN_FULL &&
2074: bms_overlap(relids, sjinfo->min_lefthand))
2075: sjinfo->delay_upper_joins = true;
The check at line 2074 is redundant and can be safely removed. If relids
doesn't initially include sjinfo->min_lefthand, then the condition at line
2056 will be met, and relids will be augmented to include the whole
sjinfo->min_lefthand at line 2060, making it overlap with
sjinfo->min_lefthand; If relids does initially include
sjinfo->min_lefthand,then it also overlap with sjinfo->min_lefthand. The
condition at 2074 is gratified anyway, so this check is removale
