*-------------------------------------------------------------------------
*/
+/*
+ * adjust_rows: tweak estimated row numbers according to the hint.
+*/
static double
adjust_rows(double rows, RowsHint *hint)
{
/*
* If it's a plain inner join, then we won't have found anything in
- * join_info_list. Make up a SpecialJoinInfo so that selectivity
+ * join_info_list. Make up a SpecialJoinInfo so that selectivity
* estimation functions will know what's being joined.
*/
if (sjinfo == NULL)
&restrictlist);
/* !!! START: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
- {
- RowsHint *rows_hint = NULL;
- int i;
-
- /* Apply appropriate Rows hint to the join node, if any. */
- for (i = 0; i < current_hint->num_hints[HINT_TYPE_ROWS]; i++)
{
- rows_hint = current_hint->rows_hints[i];
+ RowsHint *rows_hint = NULL;
+ int i;
+ RowsHint *justforme = NULL;
+ RowsHint *domultiply = NULL;
- /*
- * This Rows hint is invalid for some reason, or it contains no
- * aliasname which exists in the query.
- */
- if (!rows_hint->joinrelids ||
- rows_hint->base.state == HINT_STATE_ERROR)
- continue;
-
- if (bms_equal(joinrelids, rows_hint->joinrelids))
+ /* Search for applicable rows hint for this join node */
+ for (i = 0; i < current_hint->num_hints[HINT_TYPE_ROWS]; i++)
{
+ rows_hint = current_hint->rows_hints[i];
+
/*
- * This join RelOptInfo is exactly a Rows hint specifies, so adjust
- * rows estimateion with the hint's content. Here we never have
- * another hint which has same relation combination, so we can skip
- * rest of hints.
+ * Skip this rows_hint if it is invalid from the first or it
+ * doesn't target any join rels.
*/
- if (rows_hint->base.state == HINT_STATE_NOTUSED)
- joinrel->rows = adjust_rows(joinrel->rows, rows_hint);
+ if (!rows_hint->joinrelids ||
+ rows_hint->base.state == HINT_STATE_ERROR)
+ continue;
+
+ if (bms_equal(joinrelids, rows_hint->joinrelids))
+ {
+ /*
+ * This joinrel is just the target of this rows_hint, so tweak
+ * rows estimation according to the hint.
+ */
+ justforme = rows_hint;
+ }
+ else if (!(bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
+ bms_is_subset(rows_hint->joinrelids, rel2->relids)) &&
+ bms_is_subset(rows_hint->joinrelids, joinrelids) &&
+ rows_hint->value_type == RVT_MULTI)
+ {
+ /*
+ * If the rows_hint's target relids is not a subset of both of
+ * component rels and is a subset of this joinrel, ths hint's
+ * targets spread over both component rels. This menas that
+ * this hint has been never applied so far and this joinrel is
+ * the first (and only) chance to fire in current join tree.
+ * Only the multiplication hint has the cumulative nature so we
+ * apply only RVT_MULTI in this way.
+ */
+ domultiply = rows_hint;
+ }
}
- else if (bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
- bms_is_subset(rows_hint->joinrelids, rel2->relids))
+
+ if (justforme)
{
/*
- * Otherwise if the relation combination specified in thee Rows
- * hint is subset of the set of join elements, re-estimate rows and
- * costs again to reflect the adjustment done in down. This is
- * necessary for the first permutation of the combination the
- * relations, but it's difficult to determine that this is the
- * first, so do this everytime.
+ * If a hint just for me is found, no other adjust method is
+ * useles, but this cannot be more than twice becuase this joinrel
+ * is already adjusted by this hint.
*/
- set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
- restrictlist);
+ if (justforme->base.state == HINT_STATE_NOTUSED)
+ joinrel->rows = adjust_rows(joinrel->rows, justforme);
}
- else if (bms_is_subset(rows_hint->joinrelids, joinrelids))
+ else
{
- /*
- * If the combination specifed in the Rows hints is subset of the
- * join relation and spreads over both children,
- *
- * We do adjust rows estimation only when the value type was
- * multiplication, because other value types are meanless.
- */
- if (rows_hint->value_type == RVT_MULTI)
+ if (domultiply)
{
+ /*
+ * If we have multiple routes up to this joinrel which are not
+ * applicable this hint, this multiply hint will applied more
+ * than twice. But there's no means to know of that,
+ * re-estimate the row number of this joinrel always just
+ * before applying the hint. This is a bit different from
+ * normal planner behavior but it doesn't harm so much.
+ */
set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
restrictlist);
- joinrel->rows = adjust_rows(joinrel->rows, rows_hint);
+
+ joinrel->rows = adjust_rows(joinrel->rows, domultiply);
}
+
}
}
-
- }
/* !!! END: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
/*