}
+/*
+ * cost_subplan
+ * Figure the costs for a SubPlan (or initplan).
+ *
+ * Note: we could dig the subplan's Plan out of the root list, but in practice
+ * all callers have it handy already, so we make them pass it.
+ */
+void
+cost_subplan(PlannerInfo *root, SubPlan *subplan, Plan *plan)
+{
+ QualCost sp_cost;
+
+ /* Figure any cost for evaluating the testexpr */
+ cost_qual_eval(&sp_cost,
+ make_ands_implicit((Expr *) subplan->testexpr),
+ root);
+
+ if (subplan->useHashTable)
+ {
+ /*
+ * If we are using a hash table for the subquery outputs, then the
+ * cost of evaluating the query is a one-time cost. We charge one
+ * cpu_operator_cost per tuple for the work of loading the hashtable,
+ * too.
+ */
+ sp_cost.startup += plan->total_cost +
+ cpu_operator_cost * plan->plan_rows;
+
+ /*
+ * The per-tuple costs include the cost of evaluating the lefthand
+ * expressions, plus the cost of probing the hashtable. We already
+ * accounted for the lefthand expressions as part of the testexpr,
+ * and will also have counted one cpu_operator_cost for each
+ * comparison operator. That is probably too low for the probing
+ * cost, but it's hard to make a better estimate, so live with it for
+ * now.
+ */
+ }
+ else
+ {
+ /*
+ * Otherwise we will be rescanning the subplan output on each
+ * evaluation. We need to estimate how much of the output we will
+ * actually need to scan. NOTE: this logic should agree with the
+ * tuple_fraction estimates used by make_subplan() in
+ * plan/subselect.c.
+ */
+ Cost plan_run_cost = plan->total_cost - plan->startup_cost;
+
+ if (subplan->subLinkType == EXISTS_SUBLINK)
+ {
+ /* we only need to fetch 1 tuple */
+ sp_cost.per_tuple += plan_run_cost / plan->plan_rows;
+ }
+ else if (subplan->subLinkType == ALL_SUBLINK ||
+ subplan->subLinkType == ANY_SUBLINK)
+ {
+ /* assume we need 50% of the tuples */
+ sp_cost.per_tuple += 0.50 * plan_run_cost;
+ /* also charge a cpu_operator_cost per row examined */
+ sp_cost.per_tuple += 0.50 * plan->plan_rows * cpu_operator_cost;
+ }
+ else
+ {
+ /* assume we need all tuples */
+ sp_cost.per_tuple += plan_run_cost;
+ }
+
+ /*
+ * Also account for subplan's startup cost. If the subplan is
+ * uncorrelated or undirect correlated, AND its topmost node is a Sort
+ * or Material node, assume that we'll only need to pay its startup
+ * cost once; otherwise assume we pay the startup cost every time.
+ */
+ if (subplan->parParam == NIL &&
+ (IsA(plan, Sort) ||
+ IsA(plan, Material)))
+ sp_cost.startup += plan->startup_cost;
+ else
+ sp_cost.per_tuple += plan->startup_cost;
+ }
+
+ subplan->startup_cost = sp_cost.startup;
+ subplan->per_call_cost = sp_cost.per_tuple;
+}
+
+
/*
* cost_qual_eval
* Estimate the CPU costs of evaluating a WHERE clause.
* subplan will be executed on each evaluation, so charge accordingly.
* (Sub-selects that can be executed as InitPlans have already been
* removed from the expression.)
- *
- * An exception occurs when we have decided we can implement the
- * subplan by hashing.
*/
SubPlan *subplan = (SubPlan *) node;
- Plan *plan = planner_subplan_get_plan(context->root, subplan);
- if (subplan->useHashTable)
- {
- /*
- * If we are using a hash table for the subquery outputs, then the
- * cost of evaluating the query is a one-time cost. We charge one
- * cpu_operator_cost per tuple for the work of loading the
- * hashtable, too.
- */
- context->total.startup += plan->total_cost +
- cpu_operator_cost * plan->plan_rows;
-
- /*
- * The per-tuple costs include the cost of evaluating the lefthand
- * expressions, plus the cost of probing the hashtable. Recursion
- * into the testexpr will handle the lefthand expressions
- * properly, and will count one cpu_operator_cost for each
- * comparison operator. That is probably too low for the probing
- * cost, but it's hard to make a better estimate, so live with it
- * for now.
- */
- }
- else
- {
- /*
- * Otherwise we will be rescanning the subplan output on each
- * evaluation. We need to estimate how much of the output we will
- * actually need to scan. NOTE: this logic should agree with
- * get_initplan_cost, below, and with the estimates used by
- * make_subplan() in plan/subselect.c.
- */
- Cost plan_run_cost = plan->total_cost - plan->startup_cost;
+ context->total.startup += subplan->startup_cost;
+ context->total.per_tuple += subplan->per_call_cost;
- if (subplan->subLinkType == EXISTS_SUBLINK)
- {
- /* we only need to fetch 1 tuple */
- context->total.per_tuple += plan_run_cost / plan->plan_rows;
- }
- else if (subplan->subLinkType == ALL_SUBLINK ||
- subplan->subLinkType == ANY_SUBLINK)
- {
- /* assume we need 50% of the tuples */
- context->total.per_tuple += 0.50 * plan_run_cost;
- /* also charge a cpu_operator_cost per row examined */
- context->total.per_tuple +=
- 0.50 * plan->plan_rows * cpu_operator_cost;
- }
- else
- {
- /* assume we need all tuples */
- context->total.per_tuple += plan_run_cost;
- }
+ /*
+ * We don't want to recurse into the testexpr, because it was already
+ * counted in the SubPlan node's costs. So we're done.
+ */
+ return false;
+ }
+ else if (IsA(node, AlternativeSubPlan))
+ {
+ /*
+ * Arbitrarily use the first alternative plan for costing. (We should
+ * certainly only include one alternative, and we don't yet have
+ * enough information to know which one the executor is most likely
+ * to use.)
+ */
+ AlternativeSubPlan *asplan = (AlternativeSubPlan *) node;
- /*
- * Also account for subplan's startup cost. If the subplan is
- * uncorrelated or undirect correlated, AND its topmost node is a
- * Sort or Material node, assume that we'll only need to pay its
- * startup cost once; otherwise assume we pay the startup cost
- * every time.
- */
- if (subplan->parParam == NIL &&
- (IsA(plan, Sort) ||
- IsA(plan, Material)))
- context->total.startup += plan->startup_cost;
- else
- context->total.per_tuple += plan->startup_cost;
- }
+ return cost_qual_eval_walker((Node *) linitial(asplan->subplans),
+ context);
}
/* recurse into children */
}
-/*
- * get_initplan_cost
- * Get the expected cost of evaluating an initPlan.
- *
- * Keep this in sync with cost_qual_eval_walker's handling of subplans, above,
- * and with the estimates used by make_subplan() in plan/subselect.c.
- */
-Cost
-get_initplan_cost(PlannerInfo *root, SubPlan *subplan)
-{
- Cost result;
- Plan *plan = planner_subplan_get_plan(root, subplan);
-
- /* initPlans never use hashtables */
- Assert(!subplan->useHashTable);
- /* they are never ALL or ANY, either */
- Assert(!(subplan->subLinkType == ALL_SUBLINK ||
- subplan->subLinkType == ANY_SUBLINK));
-
- if (subplan->subLinkType == EXISTS_SUBLINK)
- {
- /* we only need to fetch 1 tuple */
- Cost plan_run_cost = plan->total_cost - plan->startup_cost;
-
- result = plan->startup_cost;
- result += plan_run_cost / plan->plan_rows;
- }
- else
- {
- /* assume we need all tuples */
- result = plan->total_cost;
- }
-
- return result;
-}
-
-
/*
* approx_tuple_count
* Quick-and-dirty estimation of the number of join rows passing
} finalize_primnode_context;
+static Node *build_subplan(PlannerInfo *root, Plan *plan, List *rtable,
+ SubLinkType subLinkType, Node *testexpr,
+ bool adjust_testexpr, bool unknownEqFalse);
static List *generate_subquery_params(PlannerInfo *root, List *tlist,
List **paramIds);
static List *generate_subquery_vars(PlannerInfo *root, List *tlist,
List *subst_nodes);
static Node *convert_testexpr_mutator(Node *node,
convert_testexpr_context *context);
-static bool subplan_is_hashable(SubLink *slink, SubPlan *node, Plan *plan);
+static bool subplan_is_hashable(Plan *plan);
+static bool testexpr_is_hashable(Node *testexpr);
static bool hash_ok_operator(OpExpr *expr);
static bool simplify_EXISTS_query(Query *query);
+static Query *convert_EXISTS_to_ANY(PlannerInfo *root, Query *subselect,
+ Node **testexpr, List **paramIds);
static Node *replace_correlation_vars_mutator(Node *node, PlannerInfo *root);
static Node *process_sublinks_mutator(Node *node,
process_sublinks_context *context);
/*
* Convert a SubLink (as created by the parser) into a SubPlan.
*
- * We are given the original SubLink and the already-processed testexpr
- * (use this instead of the SubLink's own field). We are also told if
- * this expression appears at top level of a WHERE/HAVING qual.
+ * We are given the SubLink's contained query, type, and testexpr. We are
+ * also told if this expression appears at top level of a WHERE/HAVING qual.
+ *
+ * Note: we assume that the testexpr has been AND/OR flattened (actually,
+ * it's been through eval_const_expressions), but not converted to
+ * implicit-AND form; and any SubLinks in it should already have been
+ * converted to SubPlans. The subquery is as yet untouched, however.
*
* The result is whatever we need to substitute in place of the SubLink
* node in the executable expression. This will be either the SubPlan
* tree containing InitPlan Param nodes.
*/
static Node *
-make_subplan(PlannerInfo *root, SubLink *slink, Node *testexpr, bool isTopQual)
+make_subplan(PlannerInfo *root, Query *orig_subquery, SubLinkType subLinkType,
+ Node *testexpr, bool isTopQual)
{
- Query *subquery = (Query *) (slink->subselect);
+ Query *subquery;
+ bool simple_exists = false;
double tuple_fraction;
- SubPlan *splan;
Plan *plan;
PlannerInfo *subroot;
- bool isInitPlan;
- Bitmapset *tmpset;
- int paramid;
Node *result;
/*
* same sub-Query node, but the planner wants to scribble on the Query.
* Try to clean this up when we do querytree redesign...
*/
- subquery = (Query *) copyObject(subquery);
+ subquery = (Query *) copyObject(orig_subquery);
/*
* If it's an EXISTS subplan, we might be able to simplify it.
*/
- if (slink->subLinkType == EXISTS_SUBLINK)
- (void) simplify_EXISTS_query(subquery);
+ if (subLinkType == EXISTS_SUBLINK)
+ simple_exists = simplify_EXISTS_query(subquery);
/*
* For an EXISTS subplan, tell lower-level planner to expect that only the
* first tuple will be retrieved. For ALL and ANY subplans, we will be
- * able to stop evaluating if the test condition fails, so very often not
- * all the tuples will be retrieved; for lack of a better idea, specify
- * 50% retrieval. For EXPR and ROWCOMPARE subplans, use default behavior
- * (we're only expecting one row out, anyway).
+ * able to stop evaluating if the test condition fails or matches, so very
+ * often not all the tuples will be retrieved; for lack of a better idea,
+ * specify 50% retrieval. For EXPR and ROWCOMPARE subplans, use default
+ * behavior (we're only expecting one row out, anyway).
*
- * NOTE: if you change these numbers, also change cost_qual_eval_walker()
- * and get_initplan_cost() in path/costsize.c.
+ * NOTE: if you change these numbers, also change cost_subplan() in
+ * path/costsize.c.
*
- * XXX If an ALL/ANY subplan is uncorrelated, we may decide to hash or
- * materialize its result below. In that case it would've been better to
- * specify full retrieval. At present, however, we can only detect
- * correlation or lack of it after we've made the subplan :-(. Perhaps
- * detection of correlation should be done as a separate step. Meanwhile,
- * we don't want to be too optimistic about the percentage of tuples
- * retrieved, for fear of selecting a plan that's bad for the
- * materialization case.
- */
- if (slink->subLinkType == EXISTS_SUBLINK)
+ * XXX If an ANY subplan is uncorrelated, build_subplan may decide to hash
+ * its output. In that case it would've been better to specify full
+ * retrieval. At present, however, we can only check hashability after
+ * we've made the subplan :-(. (Determining whether it'll fit in work_mem
+ * is the really hard part.) Therefore, we don't want to be too
+ * optimistic about the percentage of tuples retrieved, for fear of
+ * selecting a plan that's bad for the materialization case.
+ */
+ if (subLinkType == EXISTS_SUBLINK)
tuple_fraction = 1.0; /* just like a LIMIT 1 */
- else if (slink->subLinkType == ALL_SUBLINK ||
- slink->subLinkType == ANY_SUBLINK)
+ else if (subLinkType == ALL_SUBLINK ||
+ subLinkType == ANY_SUBLINK)
tuple_fraction = 0.5; /* 50% */
else
tuple_fraction = 0.0; /* default behavior */
tuple_fraction,
&subroot);
+ /* And convert to SubPlan or InitPlan format. */
+ result = build_subplan(root, plan, subroot->parse->rtable,
+ subLinkType, testexpr, true, isTopQual);
+
+ /*
+ * If it's a correlated EXISTS with an unimportant targetlist, we might be
+ * able to transform it to the equivalent of an IN and then implement it
+ * by hashing. We don't have enough information yet to tell which way
+ * is likely to be better (it depends on the expected number of executions
+ * of the EXISTS qual, and we are much too early in planning the outer
+ * query to be able to guess that). So we generate both plans, if
+ * possible, and leave it to the executor to decide which to use.
+ */
+ if (simple_exists && IsA(result, SubPlan))
+ {
+ Node *newtestexpr;
+ List *paramIds;
+
+ /* Make a second copy of the original subquery */
+ subquery = (Query *) copyObject(orig_subquery);
+ /* and re-simplify */
+ simple_exists = simplify_EXISTS_query(subquery);
+ Assert(simple_exists);
+ /* See if it can be converted to an ANY query */
+ subquery = convert_EXISTS_to_ANY(root, subquery,
+ &newtestexpr, ¶mIds);
+ if (subquery)
+ {
+ /* Generate the plan for the ANY subquery; we'll need all rows */
+ plan = subquery_planner(root->glob, subquery,
+ root->query_level + 1,
+ 0.0,
+ &subroot);
+
+ /* Now we can check if it'll fit in work_mem */
+ if (subplan_is_hashable(plan))
+ {
+ SubPlan *hashplan;
+ AlternativeSubPlan *asplan;
+
+ /* OK, convert to SubPlan format. */
+ hashplan = (SubPlan *) build_subplan(root, plan,
+ subroot->parse->rtable,
+ ANY_SUBLINK, newtestexpr,
+ false, true);
+ /* Check we got what we expected */
+ Assert(IsA(hashplan, SubPlan));
+ Assert(hashplan->parParam == NIL);
+ Assert(hashplan->useHashTable);
+ /* build_subplan won't have filled in paramIds */
+ hashplan->paramIds = paramIds;
+
+ /* Leave it to the executor to decide which plan to use */
+ asplan = makeNode(AlternativeSubPlan);
+ asplan->subplans = list_make2(result, hashplan);
+ result = (Node *) asplan;
+ }
+ }
+ }
+
+ return result;
+}
+
+/*
+ * Build a SubPlan node given the raw inputs --- subroutine for make_subplan
+ *
+ * Returns either the SubPlan, or an expression using initplan output Params,
+ * as explained in the comments for make_subplan.
+ */
+static Node *
+build_subplan(PlannerInfo *root, Plan *plan, List *rtable,
+ SubLinkType subLinkType, Node *testexpr,
+ bool adjust_testexpr, bool unknownEqFalse)
+{
+ Node *result;
+ SubPlan *splan;
+ bool isInitPlan;
+ Bitmapset *tmpset;
+ int paramid;
+
/*
- * Initialize the SubPlan node. Note plan_id isn't set yet.
+ * Initialize the SubPlan node. Note plan_id isn't set till further down,
+ * likewise the cost fields.
*/
splan = makeNode(SubPlan);
- splan->subLinkType = slink->subLinkType;
+ splan->subLinkType = subLinkType;
splan->testexpr = NULL;
splan->paramIds = NIL;
splan->firstColType = get_first_col_type(plan);
splan->useHashTable = false;
- /* At top level of a qual, can treat UNKNOWN the same as FALSE */
- splan->unknownEqFalse = isTopQual;
+ splan->unknownEqFalse = unknownEqFalse;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
/*
- * Make parParam list of params that current query level will pass to this
- * child plan.
+ * Make parParam and args lists of param IDs and expressions that current
+ * query level will pass to this child plan.
*/
tmpset = bms_copy(plan->extParam);
while ((paramid = bms_first_member(tmpset)) >= 0)
PlannerParamItem *pitem = list_nth(root->glob->paramlist, paramid);
if (pitem->abslevel == root->query_level)
+ {
splan->parParam = lappend_int(splan->parParam, paramid);
+ /*
+ * The Var or Aggref has already been adjusted to have the correct
+ * varlevelsup or agglevelsup. We probably don't even need to
+ * copy it again, but be safe.
+ */
+ splan->args = lappend(splan->args, copyObject(pitem->item));
+ }
}
bms_free(tmpset);
* PARAM_EXEC Params instead of the PARAM_SUBLINK Params emitted by the
* parser.
*/
- if (splan->parParam == NIL && slink->subLinkType == EXISTS_SUBLINK)
+ if (splan->parParam == NIL && subLinkType == EXISTS_SUBLINK)
{
Param *prm;
+ Assert(testexpr == NULL);
prm = generate_new_param(root, BOOLOID, -1);
splan->setParam = list_make1_int(prm->paramid);
isInitPlan = true;
result = (Node *) prm;
}
- else if (splan->parParam == NIL && slink->subLinkType == EXPR_SUBLINK)
+ else if (splan->parParam == NIL && subLinkType == EXPR_SUBLINK)
{
TargetEntry *te = linitial(plan->targetlist);
Param *prm;
Assert(!te->resjunk);
+ Assert(testexpr == NULL);
prm = generate_new_param(root,
exprType((Node *) te->expr),
exprTypmod((Node *) te->expr));
isInitPlan = true;
result = (Node *) prm;
}
- else if (splan->parParam == NIL && slink->subLinkType == ARRAY_SUBLINK)
+ else if (splan->parParam == NIL && subLinkType == ARRAY_SUBLINK)
{
TargetEntry *te = linitial(plan->targetlist);
Oid arraytype;
Param *prm;
Assert(!te->resjunk);
+ Assert(testexpr == NULL);
arraytype = get_array_type(exprType((Node *) te->expr));
if (!OidIsValid(arraytype))
elog(ERROR, "could not find array type for datatype %s",
isInitPlan = true;
result = (Node *) prm;
}
- else if (splan->parParam == NIL && slink->subLinkType == ROWCOMPARE_SUBLINK)
+ else if (splan->parParam == NIL && subLinkType == ROWCOMPARE_SUBLINK)
{
/* Adjust the Params */
List *params;
+ Assert(testexpr != NULL);
params = generate_subquery_params(root,
plan->targetlist,
&splan->paramIds);
}
else
{
- List *args;
- ListCell *l;
-
- if (testexpr)
+ /*
+ * Adjust the Params in the testexpr, unless caller said it's not
+ * needed.
+ */
+ if (testexpr && adjust_testexpr)
{
List *params;
- /* Adjust the Params in the testexpr */
params = generate_subquery_params(root,
plan->targetlist,
&splan->paramIds);
testexpr,
params);
}
+ else
+ splan->testexpr = testexpr;
/*
* We can't convert subplans of ALL_SUBLINK or ANY_SUBLINK types to
* initPlans, even when they are uncorrelated or undirect correlated,
* because we need to scan the output of the subplan for each outer
- * tuple. But if it's an IN (= ANY) test, we might be able to use a
- * hashtable to avoid comparing all the tuples.
+ * tuple. But if it's a not-direct-correlated IN (= ANY) test, we
+ * might be able to use a hashtable to avoid comparing all the tuples.
*/
- if (subplan_is_hashable(slink, splan, plan))
+ if (subLinkType == ANY_SUBLINK &&
+ splan->parParam == NIL &&
+ subplan_is_hashable(plan) &&
+ testexpr_is_hashable(splan->testexpr))
splan->useHashTable = true;
/*
plan = materialize_finished_plan(plan);
}
- /*
- * Make splan->args from parParam.
- */
- args = NIL;
- foreach(l, splan->parParam)
- {
- PlannerParamItem *pitem = list_nth(root->glob->paramlist,
- lfirst_int(l));
-
- /*
- * The Var or Aggref has already been adjusted to have the correct
- * varlevelsup or agglevelsup. We probably don't even need to
- * copy it again, but be safe.
- */
- args = lappend(args, copyObject(pitem->item));
- }
- splan->args = args;
-
result = (Node *) splan;
isInitPlan = false;
}
/*
* Add the subplan and its rtable to the global lists.
*/
- root->glob->subplans = lappend(root->glob->subplans,
- plan);
- root->glob->subrtables = lappend(root->glob->subrtables,
- subroot->parse->rtable);
+ root->glob->subplans = lappend(root->glob->subplans, plan);
+ root->glob->subrtables = lappend(root->glob->subrtables, rtable);
splan->plan_id = list_length(root->glob->subplans);
if (isInitPlan)
root->glob->rewindPlanIDs = bms_add_member(root->glob->rewindPlanIDs,
splan->plan_id);
+ /* Lastly, fill in the cost estimates for use later */
+ cost_subplan(root, splan, plan);
+
return result;
}
}
/*
- * subplan_is_hashable: decide whether we can implement a subplan by hashing
- *
- * Caution: the SubPlan node is not completely filled in yet. We can rely
- * on its plan and parParam fields, however.
+ * subplan_is_hashable: can we implement an ANY subplan by hashing?
*/
static bool
-subplan_is_hashable(SubLink *slink, SubPlan *node, Plan *plan)
+subplan_is_hashable(Plan *plan)
{
double subquery_size;
- ListCell *l;
-
- /*
- * The sublink type must be "= ANY" --- that is, an IN operator. We
- * expect that the test expression will be either a single OpExpr, or an
- * AND-clause containing OpExprs. (If it's anything else then the parser
- * must have determined that the operators have non-equality-like
- * semantics. In the OpExpr case we can't be sure what the operator's
- * semantics are like, but the test below for hashability will reject
- * anything that's not equality.)
- */
- if (slink->subLinkType != ANY_SUBLINK)
- return false;
- if (slink->testexpr == NULL ||
- (!IsA(slink->testexpr, OpExpr) &&
- !and_clause(slink->testexpr)))
- return false;
-
- /*
- * The subplan must not have any direct correlation vars --- else we'd
- * have to recompute its output each time, so that the hashtable wouldn't
- * gain anything.
- */
- if (node->parParam != NIL)
- return false;
/*
* The estimated size of the subquery result must fit in work_mem. (Note:
if (subquery_size > work_mem * 1024L)
return false;
+ return true;
+}
+
+/*
+ * testexpr_is_hashable: is an ANY SubLink's test expression hashable?
+ */
+static bool
+testexpr_is_hashable(Node *testexpr)
+{
/*
+ * The testexpr must be a single OpExpr, or an AND-clause containing
+ * only OpExprs.
+ *
* The combining operators must be hashable and strict. The need for
* hashability is obvious, since we want to use hashing. Without
* strictness, behavior in the presence of nulls is too unpredictable. We
* NULL for non-null inputs, either (see nodeSubplan.c). However, hash
* indexes and hash joins assume that too.
*/
- if (IsA(slink->testexpr, OpExpr))
+ if (testexpr && IsA(testexpr, OpExpr))
{
- if (!hash_ok_operator((OpExpr *) slink->testexpr))
- return false;
+ if (hash_ok_operator((OpExpr *) testexpr))
+ return true;
}
- else
+ else if (and_clause(testexpr))
{
- foreach(l, ((BoolExpr *) slink->testexpr)->args)
+ ListCell *l;
+
+ foreach(l, ((BoolExpr *) testexpr)->args)
{
Node *andarg = (Node *) lfirst(l);
if (!IsA(andarg, OpExpr))
- return false; /* probably can't happen */
+ return false;
if (!hash_ok_operator((OpExpr *) andarg))
return false;
}
+ return true;
}
- return true;
+ return false;
}
static bool
HeapTuple tup;
Form_pg_operator optup;
+ /* quick out if not a binary operator */
+ if (list_length(expr->args) != 2)
+ return false;
+ /* else must look up the operator properties */
tup = SearchSysCache(OPEROID,
ObjectIdGetDatum(opid),
0, 0, 0);
return true;
}
-/*
- * simplify_EXISTS_query: remove any useless stuff in an EXISTS's subquery
- *
- * The only thing that matters about an EXISTS query is whether it returns
- * zero or more than zero rows. Therefore, we can remove certain SQL features
- * that won't affect that. The only part that is really likely to matter in
- * typical usage is simplifying the targetlist: it's a common habit to write
- * "SELECT * FROM" even though there is no need to evaluate any columns.
- *
- * Note: by suppressing the targetlist we could cause an observable behavioral
- * change, namely that any errors that might occur in evaluating the tlist
- * won't occur, nor will other side-effects of volatile functions. This seems
- * unlikely to bother anyone in practice.
- *
- * Returns TRUE if was able to discard the targetlist, else FALSE.
- */
-static bool
-simplify_EXISTS_query(Query *query)
-{
- /*
- * We don't try to simplify at all if the query uses set operations,
- * aggregates, HAVING, LIMIT/OFFSET, or FOR UPDATE/SHARE; none of these
- * seem likely in normal usage and their possible effects are complex.
- */
- if (query->commandType != CMD_SELECT ||
- query->intoClause ||
- query->setOperations ||
- query->hasAggs ||
- query->havingQual ||
- query->limitOffset ||
- query->limitCount ||
- query->rowMarks)
- return false;
-
- /*
- * Mustn't throw away the targetlist if it contains set-returning
- * functions; those could affect whether zero rows are returned!
- */
- if (expression_returns_set((Node *) query->targetList))
- return false;
-
- /*
- * Otherwise, we can throw away the targetlist, as well as any GROUP,
- * DISTINCT, and ORDER BY clauses; none of those clauses will change
- * a nonzero-rows result to zero rows or vice versa. (Furthermore,
- * since our parsetree representation of these clauses depends on the
- * targetlist, we'd better throw them away if we drop the targetlist.)
- */
- query->targetList = NIL;
- query->groupClause = NIL;
- query->distinctClause = NIL;
- query->sortClause = NIL;
- query->hasDistinctOn = false;
-
- return true;
-}
-
/*
* convert_EXISTS_sublink_to_join: can we convert an EXISTS SubLink to a join?
*
return true;
}
+/*
+ * simplify_EXISTS_query: remove any useless stuff in an EXISTS's subquery
+ *
+ * The only thing that matters about an EXISTS query is whether it returns
+ * zero or more than zero rows. Therefore, we can remove certain SQL features
+ * that won't affect that. The only part that is really likely to matter in
+ * typical usage is simplifying the targetlist: it's a common habit to write
+ * "SELECT * FROM" even though there is no need to evaluate any columns.
+ *
+ * Note: by suppressing the targetlist we could cause an observable behavioral
+ * change, namely that any errors that might occur in evaluating the tlist
+ * won't occur, nor will other side-effects of volatile functions. This seems
+ * unlikely to bother anyone in practice.
+ *
+ * Returns TRUE if was able to discard the targetlist, else FALSE.
+ */
+static bool
+simplify_EXISTS_query(Query *query)
+{
+ /*
+ * We don't try to simplify at all if the query uses set operations,
+ * aggregates, HAVING, LIMIT/OFFSET, or FOR UPDATE/SHARE; none of these
+ * seem likely in normal usage and their possible effects are complex.
+ */
+ if (query->commandType != CMD_SELECT ||
+ query->intoClause ||
+ query->setOperations ||
+ query->hasAggs ||
+ query->havingQual ||
+ query->limitOffset ||
+ query->limitCount ||
+ query->rowMarks)
+ return false;
+
+ /*
+ * Mustn't throw away the targetlist if it contains set-returning
+ * functions; those could affect whether zero rows are returned!
+ */
+ if (expression_returns_set((Node *) query->targetList))
+ return false;
+
+ /*
+ * Otherwise, we can throw away the targetlist, as well as any GROUP,
+ * DISTINCT, and ORDER BY clauses; none of those clauses will change
+ * a nonzero-rows result to zero rows or vice versa. (Furthermore,
+ * since our parsetree representation of these clauses depends on the
+ * targetlist, we'd better throw them away if we drop the targetlist.)
+ */
+ query->targetList = NIL;
+ query->groupClause = NIL;
+ query->distinctClause = NIL;
+ query->sortClause = NIL;
+ query->hasDistinctOn = false;
+
+ return true;
+}
+
+/*
+ * convert_EXISTS_to_ANY: try to convert EXISTS to a hashable ANY sublink
+ *
+ * The subselect is expected to be a fresh copy that we can munge up,
+ * and to have been successfully passed through simplify_EXISTS_query.
+ *
+ * On success, the modified subselect is returned, and we store a suitable
+ * upper-level test expression at *testexpr, plus a list of the subselect's
+ * output Params at *paramIds. (The test expression is already Param-ified
+ * and hence need not go through convert_testexpr, which is why we have to
+ * deal with the Param IDs specially.)
+ *
+ * On failure, returns NULL.
+ */
+static Query *
+convert_EXISTS_to_ANY(PlannerInfo *root, Query *subselect,
+ Node **testexpr, List **paramIds)
+{
+ Node *whereClause;
+ List *leftargs,
+ *rightargs,
+ *opids,
+ *newWhere,
+ *tlist,
+ *testlist,
+ *paramids;
+ ListCell *lc,
+ *rc,
+ *oc;
+ AttrNumber resno;
+
+ /*
+ * Query must not require a targetlist, since we have to insert a new one.
+ * Caller should have dealt with the case already.
+ */
+ Assert(subselect->targetList == NIL);
+
+ /*
+ * Separate out the WHERE clause. (We could theoretically also remove
+ * top-level plain JOIN/ON clauses, but it's probably not worth the
+ * trouble.)
+ */
+ whereClause = subselect->jointree->quals;
+ subselect->jointree->quals = NULL;
+
+ /*
+ * The rest of the sub-select must not refer to any Vars of the parent
+ * query. (Vars of higher levels should be okay, though.)
+ *
+ * Note: we need not check for Aggs separately because we know the
+ * sub-select is as yet unoptimized; any uplevel Agg must therefore
+ * contain an uplevel Var reference. This is not the case below ...
+ */
+ if (contain_vars_of_level((Node *) subselect, 1))
+ return NULL;
+
+ /*
+ * We don't risk optimizing if the WHERE clause is volatile, either.
+ */
+ if (contain_volatile_functions(whereClause))
+ return NULL;
+
+ /*
+ * Clean up the WHERE clause by doing const-simplification etc on it.
+ * Aside from simplifying the processing we're about to do, this is
+ * important for being able to pull chunks of the WHERE clause up into
+ * the parent query. Since we are invoked partway through the parent's
+ * preprocess_expression() work, earlier steps of preprocess_expression()
+ * wouldn't get applied to the pulled-up stuff unless we do them here.
+ * For the parts of the WHERE clause that get put back into the child
+ * query, this work is partially duplicative, but it shouldn't hurt.
+ *
+ * Note: we do not run flatten_join_alias_vars. This is OK because
+ * any parent aliases were flattened already, and we're not going to
+ * pull any child Vars (of any description) into the parent.
+ *
+ * Note: passing the parent's root to eval_const_expressions is technically
+ * wrong, but we can get away with it since only the boundParams (if any)
+ * are used, and those would be the same in a subroot.
+ */
+ whereClause = eval_const_expressions(root, whereClause);
+ whereClause = (Node *) canonicalize_qual((Expr *) whereClause);
+ whereClause = (Node *) make_ands_implicit((Expr *) whereClause);
+
+ /*
+ * We now have a flattened implicit-AND list of clauses, which we
+ * try to break apart into "outervar = innervar" hash clauses.
+ * Anything that can't be broken apart just goes back into the
+ * newWhere list. Note that we aren't trying hard yet to ensure
+ * that we have only outer or only inner on each side; we'll check
+ * that if we get to the end.
+ */
+ leftargs = rightargs = opids = newWhere = NIL;
+ foreach(lc, (List *) whereClause)
+ {
+ OpExpr *expr = (OpExpr *) lfirst(lc);
+
+ if (IsA(expr, OpExpr) &&
+ hash_ok_operator(expr))
+ {
+ Node *leftarg = (Node *) linitial(expr->args);
+ Node *rightarg = (Node *) lsecond(expr->args);
+
+ if (contain_vars_of_level(leftarg, 1))
+ {
+ leftargs = lappend(leftargs, leftarg);
+ rightargs = lappend(rightargs, rightarg);
+ opids = lappend_oid(opids, expr->opno);
+ continue;
+ }
+ if (contain_vars_of_level(rightarg, 1))
+ {
+ /*
+ * We must commute the clause to put the outer var on the
+ * left, because the hashing code in nodeSubplan.c expects
+ * that. This probably shouldn't ever fail, since hashable
+ * operators ought to have commutators, but be paranoid.
+ */
+ expr->opno = get_commutator(expr->opno);
+ if (OidIsValid(expr->opno) && hash_ok_operator(expr))
+ {
+ leftargs = lappend(leftargs, rightarg);
+ rightargs = lappend(rightargs, leftarg);
+ opids = lappend_oid(opids, expr->opno);
+ continue;
+ }
+ /* If no commutator, no chance to optimize the WHERE clause */
+ return NULL;
+ }
+ }
+ /* Couldn't handle it as a hash clause */
+ newWhere = lappend(newWhere, expr);
+ }
+
+ /*
+ * If we didn't find anything we could convert, fail.
+ */
+ if (leftargs == NIL)
+ return NULL;
+
+ /*
+ * There mustn't be any parent Vars or Aggs in the stuff that we intend to
+ * put back into the child query. Note: you might think we don't need to
+ * check for Aggs separately, because an uplevel Agg must contain an
+ * uplevel Var in its argument. But it is possible that the uplevel Var
+ * got optimized away by eval_const_expressions. Consider
+ *
+ * SUM(CASE WHEN false THEN uplevelvar ELSE 0 END)
+ */
+ if (contain_vars_of_level((Node *) newWhere, 1) ||
+ contain_vars_of_level((Node *) rightargs, 1))
+ return NULL;
+ if (root->parse->hasAggs &&
+ (contain_aggs_of_level((Node *) newWhere, 1) ||
+ contain_aggs_of_level((Node *) rightargs, 1)))
+ return NULL;
+
+ /*
+ * And there can't be any child Vars in the stuff we intend to pull up.
+ * (Note: we'd need to check for child Aggs too, except we know the
+ * child has no aggs at all because of simplify_EXISTS_query's check.)
+ */
+ if (contain_vars_of_level((Node *) leftargs, 0))
+ return NULL;
+
+ /*
+ * Also reject sublinks in the stuff we intend to pull up. (It might be
+ * possible to support this, but doesn't seem worth the complication.)
+ */
+ if (contain_subplans((Node *) leftargs))
+ return NULL;
+
+ /*
+ * Okay, adjust the sublevelsup in the stuff we're pulling up.
+ */
+ IncrementVarSublevelsUp((Node *) leftargs, -1, 1);
+
+ /*
+ * Put back any child-level-only WHERE clauses.
+ */
+ if (newWhere)
+ subselect->jointree->quals = (Node *) make_ands_explicit(newWhere);
+
+ /*
+ * Build a new targetlist for the child that emits the expressions
+ * we need. Concurrently, build a testexpr for the parent using
+ * Params to reference the child outputs. (Since we generate Params
+ * directly here, there will be no need to convert the testexpr in
+ * build_subplan.)
+ */
+ tlist = testlist = paramids = NIL;
+ resno = 1;
+ /* there's no "for3" so we have to chase one of the lists manually */
+ oc = list_head(opids);
+ forboth(lc, leftargs, rc, rightargs)
+ {
+ Node *leftarg = (Node *) lfirst(lc);
+ Node *rightarg = (Node *) lfirst(rc);
+ Oid opid = lfirst_oid(oc);
+ Param *param;
+
+ oc = lnext(oc);
+ param = generate_new_param(root,
+ exprType(rightarg),
+ exprTypmod(rightarg));
+ tlist = lappend(tlist,
+ makeTargetEntry((Expr *) rightarg,
+ resno++,
+ NULL,
+ false));
+ testlist = lappend(testlist,
+ make_opclause(opid, BOOLOID, false,
+ (Expr *) leftarg, (Expr *) param));
+ paramids = lappend_int(paramids, param->paramid);
+ }
+
+ /* Put everything where it should go, and we're done */
+ subselect->targetList = tlist;
+ *testexpr = (Node *) make_ands_explicit(testlist);
+ *paramIds = paramids;
+
+ return subselect;
+}
+
+
/*
* Replace correlation vars (uplevel vars) with Params.
*
* Now build the SubPlan node and make the expr to return.
*/
return make_subplan(context->root,
- sublink,
+ (Query *) sublink->subselect,
+ sublink->subLinkType,
testexpr,
context->isTopQual);
}
* the very routine that creates 'em to begin with). We shouldn't find
* ourselves invoked directly on a Query, either.
*/
- Assert(!is_subplan(node));
+ Assert(!IsA(node, SubPlan));
+ Assert(!IsA(node, AlternativeSubPlan));
Assert(!IsA(node, Query));
/*
{
initSetParam = bms_add_member(initSetParam, lfirst_int(l2));
}
- initplan_cost += get_initplan_cost(root, initsubplan);
+ initplan_cost += initsubplan->startup_cost + initsubplan->per_call_cost;
}
/*
}
return false; /* no more to do here */
}
- if (is_subplan(node))
+ if (IsA(node, SubPlan))
{
SubPlan *subplan = (SubPlan *) node;
Plan *plan = planner_subplan_get_plan(context->root, subplan);
* parParam and args lists remain empty.
*/
+ cost_subplan(root, node, plan);
+
/*
* Make a Param that will be the subplan's output.
*/
projects / users / simon / postgres.git / commitdiff