(2019/01/11 13:46), Amit Langote wrote:
On 2019/01/10 15:07, Etsuro Fujita wrote:
(2019/01/10 10:41), Amit Langote wrote:
That's a loaded meaning and abusing it to mean something else can be
challenged, but we can live with that if properly documented. Speaking of
which:
/* used by partitionwise joins: */
bool consider_partitionwise_join; /* consider
partitionwise join
* paths? (if partitioned
rel) */
Maybe, mention here how it will be abused in back-branches for
non-partitioned relations?
Will do.
Thank you.
I know we don't yet reach a consensus on what to do in details to
address this issue, but for the above, how about adding comments like
this to set_append_rel_size(), instead of the header file:
/*
* If we consider partitionwise joins with the parent rel, do
the same
* for partitioned child rels.
*
* Note: here we abuse the consider_partitionwise_join flag for
child
* rels that are not partitioned, to tell try_partitionwise_join()
* that their targetlists and EC entries have been generated.
*/
if (rel->consider_partitionwise_join)
childrel->consider_partitionwise_join = true;
ISTM that that would be more clearer than the header file.
Updated patch attached, which also updated other comments a little bit.
Best regards,
Etsuro Fujita
*** a/src/backend/optimizer/path/allpaths.c
--- b/src/backend/optimizer/path/allpaths.c
***************
*** 1018,1059 **** set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
/*
! * Copy/Modify targetlist. Even if this child is deemed empty, we need
! * its targetlist in case it falls on nullable side in a child-join
! * because of partitionwise join.
! *
! * NB: the resulting childrel->reltarget->exprs may contain arbitrary
! * expressions, which otherwise would not occur in a rel's targetlist.
! * Code that might be looking at an appendrel child must cope with
! * such. (Normally, a rel's targetlist would only include Vars and
! * PlaceHolderVars.) XXX we do not bother to update the cost or width
! * fields of childrel->reltarget; not clear if that would be useful.
! */
! childrel->reltarget->exprs = (List *)
! adjust_appendrel_attrs(root,
! (Node *) rel->reltarget->exprs,
! 1, &appinfo);
!
! /*
! * We have to make child entries in the EquivalenceClass data
! * structures as well. This is needed either if the parent
! * participates in some eclass joins (because we will want to consider
! * inner-indexscan joins on the individual children) or if the parent
! * has useful pathkeys (because we should try to build MergeAppend
! * paths that produce those sort orderings). Even if this child is
! * deemed dummy, it may fall on nullable side in a child-join, which
! * in turn may participate in a MergeAppend, where we will need the
! * EquivalenceClass data structures.
! */
! if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
! add_child_rel_equivalences(root, appinfo, rel, childrel);
! childrel->has_eclass_joins = rel->has_eclass_joins;
!
! /*
! * We have to copy the parent's quals to the child, with appropriate
! * substitution of variables. However, only the baserestrictinfo
! * quals are needed before we can check for constraint exclusion; so
! * do that first and then check to see if we can disregard this child.
*
* The child rel's targetlist might contain non-Var expressions, which
* means that substitution into the quals could produce opportunities
--- 1018,1028 ----
Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
/*
! * We have to copy the parent's targetlist and quals to the child,
! * with appropriate substitution of variables. However, only the
! * baserestrictinfo quals are needed before we can check for
! * constraint exclusion; so do that first and then check to see if we
! * can disregard this child.
*
* The child rel's targetlist might contain non-Var expressions, which
* means that substitution into the quals could produce opportunities
***************
*** 1187,1197 **** set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
continue;
}
! /* CE failed, so finish copying/modifying join quals. */
childrel->joininfo = (List *)
adjust_appendrel_attrs(root,
(Node *) rel->joininfo,
1, &appinfo);
/*
* Note: we could compute appropriate attr_needed data for the child's
--- 1156,1191 ----
continue;
}
! /*
! * CE failed, so finish copying/modifying targetlist and join quals.
! *
! * NB: the resulting childrel->reltarget->exprs may contain arbitrary
! * expressions, which otherwise would not occur in a rel's targetlist.
! * Code that might be looking at an appendrel child must cope with
! * such. (Normally, a rel's targetlist would only include Vars and
! * PlaceHolderVars.) XXX we do not bother to update the cost or width
! * fields of childrel->reltarget; not clear if that would be useful.
! */
childrel->joininfo = (List *)
adjust_appendrel_attrs(root,
(Node *) rel->joininfo,
1, &appinfo);
+ childrel->reltarget->exprs = (List *)
+ adjust_appendrel_attrs(root,
+ (Node *) rel->reltarget->exprs,
+ 1, &appinfo);
+
+ /*
+ * We have to make child entries in the EquivalenceClass data
+ * structures as well. This is needed either if the parent
+ * participates in some eclass joins (because we will want to consider
+ * inner-indexscan joins on the individual children) or if the parent
+ * has useful pathkeys (because we should try to build MergeAppend
+ * paths that produce those sort orderings).
+ */
+ if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
+ add_child_rel_equivalences(root, appinfo, rel, childrel);
+ childrel->has_eclass_joins = rel->has_eclass_joins;
/*
* Note: we could compute appropriate attr_needed data for the child's
***************
*** 1204,1212 **** set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
/*
* If we consider partitionwise joins with the parent rel, do the same
* for partitioned child rels.
*/
! if (rel->consider_partitionwise_join &&
! childRTE->relkind == RELKIND_PARTITIONED_TABLE)
childrel->consider_partitionwise_join = true;
/*
--- 1198,1209 ----
/*
* If we consider partitionwise joins with the parent rel, do the same
* for partitioned child rels.
+ *
+ * Note: here we abuse the consider_partitionwise_join flag for child
+ * rels that are not partitioned, to tell try_partitionwise_join()
+ * that their targetlists and EC entries have been generated.
*/
! if (rel->consider_partitionwise_join)
childrel->consider_partitionwise_join = true;
/*
*** a/src/backend/optimizer/path/joinrels.c
--- b/src/backend/optimizer/path/joinrels.c
***************
*** 44,49 **** static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1,
--- 44,51 ----
RelOptInfo *rel2, RelOptInfo *joinrel,
SpecialJoinInfo *parent_sjinfo,
List *parent_restrictlist);
+ static void update_child_rel_info(PlannerInfo *root,
+ RelOptInfo *rel, RelOptInfo *childrel);
static int match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel,
bool strict_op);
***************
*** 1312,1317 **** try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
--- 1314,1321 ----
RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo,
List *parent_restrictlist)
{
+ bool rel1_is_simple = IS_SIMPLE_REL(rel1);
+ bool rel2_is_simple = IS_SIMPLE_REL(rel2);
int nparts;
int cnt_parts;
***************
*** 1376,1381 **** try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
--- 1380,1406 ----
AppendRelInfo **appinfos;
int nappinfos;
+ /*
+ * If a child table has consider_partitionwise_join=false, it means
+ * that it's a dummy relation for which we skipped setting up tlist
+ * expressions and adding EC members in set_append_rel_size(), so do
+ * that now for use later.
+ */
+ if (rel1_is_simple && !child_rel1->consider_partitionwise_join)
+ {
+ Assert(child_rel1->reloptkind == RELOPT_OTHER_MEMBER_REL);
+ Assert(IS_DUMMY_REL(child_rel1));
+ update_child_rel_info(root, rel1, child_rel1);
+ child_rel1->consider_partitionwise_join = true;
+ }
+ if (rel2_is_simple && !child_rel2->consider_partitionwise_join)
+ {
+ Assert(child_rel2->reloptkind == RELOPT_OTHER_MEMBER_REL);
+ Assert(IS_DUMMY_REL(child_rel2));
+ update_child_rel_info(root, rel2, child_rel2);
+ child_rel2->consider_partitionwise_join = true;
+ }
+
/* We should never try to join two overlapping sets of rels. */
Assert(!bms_overlap(child_rel1->relids, child_rel2->relids));
child_joinrelids = bms_union(child_rel1->relids, child_rel2->relids);
***************
*** 1417,1422 **** try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
--- 1442,1469 ----
}
}
+ /*
+ * Set up tlist expressions for the childrel, and add EC members referencing
+ * the childrel.
+ */
+ static void
+ update_child_rel_info(PlannerInfo *root,
+ RelOptInfo *rel, RelOptInfo *childrel)
+ {
+ AppendRelInfo *appinfo = root->append_rel_array[childrel->relid];
+
+ /* Make child tlist expressions */
+ childrel->reltarget->exprs = (List *)
+ adjust_appendrel_attrs(root,
+ (Node *) rel->reltarget->exprs,
+ 1, &appinfo);
+
+ /* Make child entries in the EquivalenceClass as well */
+ if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
+ add_child_rel_equivalences(root, appinfo, rel, childrel);
+ childrel->has_eclass_joins = rel->has_eclass_joins;
+ }
+
/*
* Returns true if there exists an equi-join condition for each pair of
* partition keys from given relations being joined.
