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2022年8月17日 19:35:51 +0000 (15:35 -0400)

Up to now we've just searched the placeholder_list when we want to
find the PlaceHolderInfo with a given ID. While there's no evidence
of that being a problem in the field, an upcoming patch will add
find_placeholder_info() calls in build_joinrel_tlist(), which seems
likely to make it more of an issue: a joinrel emitting lots of
PlaceHolderVars would incur O(N^2) cost, and we might be building
a lot of joinrels in complex queries. Hence, add an array that
can be indexed directly by phid to make the lookups constant-time.

Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us

src/backend/optimizer/plan/analyzejoins.c patch | blob | blame | history

src/backend/optimizer/plan/planmain.c patch | blob | blame | history

src/backend/optimizer/util/placeholder.c patch | blob | blame | history

src/backend/optimizer/util/var.c patch | blob | blame | history

src/include/nodes/pathnodes.h patch | blob | blame | history

diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c

index 337f470d58346f572a5f6a165cafc315178315be..bbeca9a9abe78beb2858b34ada95b059313ac6aa 100644 (file)

--- a/src/backend/optimizer/plan/analyzejoins.c

+++ b/src/backend/optimizer/plan/analyzejoins.c

@@ -388,8 +388,11 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)

Assert(!bms_is_member(relid, phinfo->ph_lateral));

if (bms_is_subset(phinfo->ph_needed, joinrelids) &&

bms_is_member(relid, phinfo->ph_eval_at))

+ {

root->placeholder_list = foreach_delete_current(root->placeholder_list,

l);

+ root->placeholder_array[phinfo->phid] = NULL;

+ }

else

{

phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at, relid);

diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c

index c92ddd27ed10c592b12c907f1cbc16f42637b4e9..248cde4d9bdb2991e5becd4afb8866425475f5a9 100644 (file)

--- a/src/backend/optimizer/plan/planmain.c

+++ b/src/backend/optimizer/plan/planmain.c

@@ -75,6 +75,8 @@ query_planner(PlannerInfo *root,

root->full_join_clauses = NIL;

root->join_info_list = NIL;

root->placeholder_list = NIL;

+ root->placeholder_array = NULL;

+ root->placeholder_array_size = 0;

root->fkey_list = NIL;

root->initial_rels = NIL;

diff --git a/src/backend/optimizer/util/placeholder.c b/src/backend/optimizer/util/placeholder.c

index 3b0f0584f0174682f356876302d89d4149d8e4b3..0184e6d36c13f43e385a868fa69b8cf66b5237b7 100644 (file)

--- a/src/backend/optimizer/util/placeholder.c

+++ b/src/backend/optimizer/util/placeholder.c

@@ -71,16 +71,19 @@ find_placeholder_info(PlannerInfo *root, PlaceHolderVar *phv,

{

PlaceHolderInfo *phinfo;

Relids rels_used;

- ListCell *lc;

/* if this ever isn't true, we'd need to be able to look in parent lists */

Assert(phv->phlevelsup == 0);

- foreach(lc, root->placeholder_list)

+ /* Use placeholder_array to look up existing PlaceHolderInfo quickly */

+ if (phv->phid < root->placeholder_array_size)

+ phinfo = root->placeholder_array[phv->phid];

+ else

+ phinfo = NULL;

+ if (phinfo != NULL)

{

- phinfo = (PlaceHolderInfo *) lfirst(lc);

- if (phinfo->phid == phv->phid)

- return phinfo;

+ Assert(phinfo->phid == phv->phid);

+ return phinfo;

}

/* Not found, so create it */

@@ -115,8 +118,38 @@ find_placeholder_info(PlannerInfo *root, PlaceHolderVar *phv,

phinfo->ph_width = get_typavgwidth(exprType((Node *) phv->phexpr),

exprTypmod((Node *) phv->phexpr));

+ /*

+ * Add to both placeholder_list and placeholder_array. Note: because we

+ * store pointers to the PlaceHolderInfos in two data structures, it'd be

+ * unsafe to pass the whole placeholder_list structure through

+ * expression_tree_mutator or the like --- or at least, you'd have to

+ * rebuild the placeholder_array afterwards.

+ */

root->placeholder_list = lappend(root->placeholder_list, phinfo);

+ if (phinfo->phid >= root->placeholder_array_size)

+ {

+ /* Must allocate or enlarge placeholder_array */

+ int new_size;

+ new_size = root->placeholder_array_size ? root->placeholder_array_size * 2 : 8;

+ while (phinfo->phid >= new_size)

+ new_size *= 2;

+ if (root->placeholder_array)

+ {

+ root->placeholder_array = (PlaceHolderInfo **)

+ repalloc(root->placeholder_array,

+ sizeof(PlaceHolderInfo *) * new_size);

+ MemSet(root->placeholder_array + root->placeholder_array_size, 0,

+ sizeof(PlaceHolderInfo *) * (new_size - root->placeholder_array_size));

+ }

+ else

+ root->placeholder_array = (PlaceHolderInfo **)

+ palloc0(new_size * sizeof(PlaceHolderInfo *));

+ root->placeholder_array_size = new_size;

+ }

+ root->placeholder_array[phinfo->phid] = phinfo;

* The PHV's contained expression may contain other, lower-level PHVs. We

* now know we need to get those into the PlaceHolderInfo list, too, so we

diff --git a/src/backend/optimizer/util/var.c b/src/backend/optimizer/util/var.c

index ebc6ce84b0bdcffe5b303aaef3e4b5f88362b65a..7db86c39efcf97aa18f16702b58a583fb5713dd8 100644 (file)

--- a/src/backend/optimizer/util/var.c

+++ b/src/backend/optimizer/util/var.c

@@ -210,15 +210,8 @@ pull_varnos_walker(Node *node, pull_varnos_context *context)

if (phv->phlevelsup == 0)

{

- ListCell *lc;

- foreach(lc, context->root->placeholder_list)

- {

- phinfo = (PlaceHolderInfo *) lfirst(lc);

- if (phinfo->phid == phv->phid)

- break;

- phinfo = NULL;

- }

+ if (phv->phid < context->root->placeholder_array_size)

+ phinfo = context->root->placeholder_array[phv->phid];

}

if (phinfo == NULL)

{

diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h

index 3b065139e68d61952eadf936319ec6609c753949..b310d3c6fd336c34bb8fccd340e5e55f9679089d 100644 (file)

--- a/src/include/nodes/pathnodes.h

+++ b/src/include/nodes/pathnodes.h

@@ -357,6 +357,11 @@ struct PlannerInfo

/* list of PlaceHolderInfos */

List *placeholder_list;

+ /* array of PlaceHolderInfos indexed by phid */

+ struct PlaceHolderInfo **placeholder_array pg_node_attr(read_write_ignore, array_size(placeholder_array_size));

+ /* allocated size of array */

+ int placeholder_array_size pg_node_attr(read_write_ignore);

/* list of ForeignKeyOptInfos */

List *fkey_list;

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