* reduce_outer_joins
*
*
- * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
PlannerInfo *root;
List *targetlist; /* tlist of subquery being pulled up */
RangeTblEntry *target_rte; /* RTE of subquery */
+ Relids relids; /* relids within subquery, as numbered after
+ * pullup (set only if target_rte->lateral) */
bool *outer_hasSubLinks; /* -> outer query's hasSubLinks */
int varno; /* varno of subquery */
bool need_phvs; /* do we need PlaceHolderVars? */
static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
- AppendRelInfo *containing_appendrel);
+ AppendRelInfo *containing_appendrel,
+ bool deletion_ok);
static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
- AppendRelInfo *containing_appendrel);
+ AppendRelInfo *containing_appendrel,
+ bool deletion_ok);
static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
RangeTblEntry *rte);
static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
static void make_setop_translation_list(Query *query, Index newvarno,
List **translated_vars);
static bool is_simple_subquery(Query *subquery, RangeTblEntry *rte,
- JoinExpr *lowest_outer_join);
+ JoinExpr *lowest_outer_join,
+ bool deletion_ok);
+static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
+ RangeTblEntry *rte);
+static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte,
+ bool deletion_ok);
static bool is_simple_union_all(Query *subquery);
static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
List *colTypes);
static bool is_safe_append_member(Query *subquery);
+static bool jointree_contains_lateral_outer_refs(Node *jtnode, bool restricted,
+ Relids safe_upper_varnos);
static void replace_vars_in_jointree(Node *jtnode,
pullup_replace_vars_context *context,
JoinExpr *lowest_nulling_outer_join);
replace_rte_variables_context *context);
static Query *pullup_replace_vars_subquery(Query *query,
pullup_replace_vars_context *context);
+static Node *pull_up_subqueries_cleanup(Node *jtnode);
static reduce_outer_joins_state *reduce_outer_joins_pass1(Node *jtnode);
static void reduce_outer_joins_pass2(Node *jtnode,
reduce_outer_joins_state *state,
*
* A clause "foo op ANY (sub-SELECT)" can be processed by pulling the
* sub-SELECT up to become a rangetable entry and treating the implied
- * comparisons as quals of a semijoin. However, this optimization *only*
+ * comparisons as quals of a semijoin. However, this optimization *only*
* works at the top level of WHERE or a JOIN/ON clause, because we cannot
* distinguish whether the ANY ought to return FALSE or NULL in cases
* involving NULL inputs. Also, in an outer join's ON clause we can only
* transformations if any are found.
*
* This routine has to run before preprocess_expression(), so the quals
- * clauses are not yet reduced to implicit-AND format. That means we need
- * to recursively search through explicit AND clauses, which are
- * probably only binary ANDs. We stop as soon as we hit a non-AND item.
+ * clauses are not yet reduced to implicit-AND format, and are not guaranteed
+ * to be AND/OR-flat either. That means we need to recursively search through
+ * explicit AND clauses. We stop as soon as we hit a non-AND item.
*/
void
pull_up_sublinks(PlannerInfo *root)
/*
* Although we could include the pulled-up subqueries in the returned
* relids, there's no need since upper quals couldn't refer to their
- * outputs anyway. But we *do* need to include the join's own rtindex
+ * outputs anyway. But we *do* need to include the join's own rtindex
* because we haven't yet collapsed join alias variables, so upper
* levels would mistakenly think they couldn't use references to this
* join.
/* Successful expansion, replace the rtable entry */
rte->rtekind = RTE_SUBQUERY;
rte->subquery = funcquery;
- rte->funcexpr = NULL;
- rte->funccoltypes = NIL;
- rte->funccoltypmods = NIL;
- rte->funccolcollations = NIL;
+ rte->functions = NIL;
}
}
}
* grouping/aggregation then we can merge it into the parent's jointree.
* Also, subqueries that are simple UNION ALL structures can be
* converted into "append relations".
- *
- * This recursively processes the jointree and returns a modified jointree.
*/
-Node *
-pull_up_subqueries(PlannerInfo *root, Node *jtnode)
+void
+pull_up_subqueries(PlannerInfo *root)
{
- /* Start off with no containing join nor appendrel */
- return pull_up_subqueries_recurse(root, jtnode, NULL, NULL, NULL);
+ /* Top level of jointree must always be a FromExpr */
+ Assert(IsA(root->parse->jointree, FromExpr));
+ /* Reset flag saying we need a deletion cleanup pass */
+ root->hasDeletedRTEs = false;
+ /* Recursion starts with no containing join nor appendrel */
+ root->parse->jointree = (FromExpr *)
+ pull_up_subqueries_recurse(root, (Node *) root->parse->jointree,
+ NULL, NULL, NULL, false);
+ /* Apply cleanup phase if necessary */
+ if (root->hasDeletedRTEs)
+ root->parse->jointree = (FromExpr *)
+ pull_up_subqueries_cleanup((Node *) root->parse->jointree);
+ Assert(IsA(root->parse->jointree, FromExpr));
}
/*
* pull_up_subqueries_recurse
* Recursive guts of pull_up_subqueries.
*
+ * This recursively processes the jointree and returns a modified jointree.
+ * Or, if it's valid to drop the current node from the jointree completely,
+ * it returns NULL.
+ *
* If this jointree node is within either side of an outer join, then
* lowest_outer_join references the lowest such JoinExpr node; otherwise
* it is NULL. We use this to constrain the effects of LATERAL subqueries.
* This forces use of the PlaceHolderVar mechanism for all non-Var targetlist
* items, and puts some additional restrictions on what can be pulled up.
*
+ * deletion_ok is TRUE if the caller can cope with us returning NULL for a
+ * deletable leaf node (for example, a VALUES RTE that could be pulled up).
+ * If it's FALSE, we'll avoid pullup in such cases.
+ *
* A tricky aspect of this code is that if we pull up a subquery we have
* to replace Vars that reference the subquery's outputs throughout the
* parent query, including quals attached to jointree nodes above the one
* we are currently processing! We handle this by being careful not to
- * change the jointree structure while recursing: no nodes other than
- * subquery RangeTblRef entries will be replaced. Also, we can't turn
- * pullup_replace_vars loose on the whole jointree, because it'll return a
- * mutated copy of the tree; we have to invoke it just on the quals, instead.
- * This behavior is what makes it reasonable to pass lowest_outer_join and
- * lowest_nulling_outer_join as pointers rather than some more-indirect way
- * of identifying the lowest OJs. Likewise, we don't replace append_rel_list
- * members but only their substructure, so the containing_appendrel reference
- * is safe to use.
+ * change the jointree structure while recursing: no nodes other than leaf
+ * RangeTblRef entries and entirely-empty FromExprs will be replaced or
+ * deleted. Also, we can't turn pullup_replace_vars loose on the whole
+ * jointree, because it'll return a mutated copy of the tree; we have to
+ * invoke it just on the quals, instead. This behavior is what makes it
+ * reasonable to pass lowest_outer_join and lowest_nulling_outer_join as
+ * pointers rather than some more-indirect way of identifying the lowest
+ * OJs. Likewise, we don't replace append_rel_list members but only their
+ * substructure, so the containing_appendrel reference is safe to use.
+ *
+ * Because of the rule that no jointree nodes with substructure can be
+ * replaced, we cannot fully handle the case of deleting nodes from the tree:
+ * when we delete one child of a JoinExpr, we need to replace the JoinExpr
+ * with a FromExpr, and that can't happen here. Instead, we set the
+ * root->hasDeletedRTEs flag, which tells pull_up_subqueries() that an
+ * additional pass over the tree is needed to clean up.
*/
static Node *
pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
- AppendRelInfo *containing_appendrel)
+ AppendRelInfo *containing_appendrel,
+ bool deletion_ok)
{
- if (jtnode == NULL)
- return NULL;
+ Assert(jtnode != NULL);
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
* unless is_safe_append_member says so.
*/
if (rte->rtekind == RTE_SUBQUERY &&
- is_simple_subquery(rte->subquery, rte, lowest_outer_join) &&
+ is_simple_subquery(rte->subquery, rte,
+ lowest_outer_join, deletion_ok) &&
(containing_appendrel == NULL ||
is_safe_append_member(rte->subquery)))
return pull_up_simple_subquery(root, jtnode, rte,
lowest_outer_join,
lowest_nulling_outer_join,
- containing_appendrel);
+ containing_appendrel,
+ deletion_ok);
/*
* Alternatively, is it a simple UNION ALL subquery? If so, flatten
is_simple_union_all(rte->subquery))
return pull_up_simple_union_all(root, jtnode, rte);
+ /*
+ * Or perhaps it's a simple VALUES RTE?
+ *
+ * We don't allow VALUES pullup below an outer join nor into an
+ * appendrel (such cases are impossible anyway at the moment).
+ */
+ if (rte->rtekind == RTE_VALUES &&
+ lowest_outer_join == NULL &&
+ containing_appendrel == NULL &&
+ is_simple_values(root, rte, deletion_ok))
+ return pull_up_simple_values(root, jtnode, rte);
+
/* Otherwise, do nothing at this node. */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
+ bool have_undeleted_child = false;
ListCell *l;
Assert(containing_appendrel == NULL);
+
+ /*
+ * If the FromExpr has quals, it's not deletable even if its parent
+ * would allow deletion.
+ */
+ if (f->quals)
+ deletion_ok = false;
+
foreach(l, f->fromlist)
+ {
+ /*
+ * In a non-deletable FromExpr, we can allow deletion of child
+ * nodes so long as at least one child remains; so it's okay
+ * either if any previous child survives, or if there's more to
+ * come. If all children are deletable in themselves, we'll force
+ * the last one to remain unflattened.
+ *
+ * As a separate matter, we can allow deletion of all children of
+ * the top-level FromExpr in a query, since that's a special case
+ * anyway.
+ */
+ bool sub_deletion_ok = (deletion_ok ||
+ have_undeleted_child ||
+ lnext(l) != NULL ||
+ f == root->parse->jointree);
+
lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
lowest_outer_join,
lowest_nulling_outer_join,
- NULL);
+ NULL,
+ sub_deletion_ok);
+ if (lfirst(l) != NULL)
+ have_undeleted_child = true;
+ }
+
+ if (deletion_ok && !have_undeleted_child)
+ {
+ /* OK to delete this FromExpr entirely */
+ root->hasDeletedRTEs = true; /* probably is set already */
+ return NULL;
+ }
}
else if (IsA(jtnode, JoinExpr))
{
switch (j->jointype)
{
case JOIN_INNER:
+
+ /*
+ * INNER JOIN can allow deletion of either child node, but not
+ * both. So right child gets permission to delete only if
+ * left child didn't get removed.
+ */
j->larg = pull_up_subqueries_recurse(root, j->larg,
lowest_outer_join,
- lowest_nulling_outer_join,
- NULL);
+ lowest_nulling_outer_join,
+ NULL,
+ true);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
lowest_outer_join,
- lowest_nulling_outer_join,
- NULL);
+ lowest_nulling_outer_join,
+ NULL,
+ j->larg != NULL);
break;
case JOIN_LEFT:
case JOIN_SEMI:
case JOIN_ANTI:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
- lowest_nulling_outer_join,
- NULL);
+ lowest_nulling_outer_join,
+ NULL,
+ false);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
j,
- NULL);
+ NULL,
+ false);
break;
case JOIN_FULL:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
j,
- NULL);
+ NULL,
+ false);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
j,
- NULL);
+ NULL,
+ false);
break;
case JOIN_RIGHT:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
j,
- NULL);
+ NULL,
+ false);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
j,
- lowest_nulling_outer_join,
- NULL);
+ lowest_nulling_outer_join,
+ NULL,
+ false);
break;
default:
elog(ERROR, "unrecognized join type: %d",
* Attempt to pull up a single simple subquery.
*
* jtnode is a RangeTblRef that has been tentatively identified as a simple
- * subquery by pull_up_subqueries. We return the replacement jointree node,
- * or jtnode itself if we determine that the subquery can't be pulled up after
- * all.
+ * subquery by pull_up_subqueries. We return the replacement jointree node,
+ * or NULL if the subquery can be deleted entirely, or jtnode itself if we
+ * determine that the subquery can't be pulled up after all.
*
* rte is the RangeTblEntry referenced by jtnode. Remaining parameters are
* as for pull_up_subqueries_recurse.
pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
JoinExpr *lowest_outer_join,
JoinExpr *lowest_nulling_outer_join,
- AppendRelInfo *containing_appendrel)
+ AppendRelInfo *containing_appendrel,
+ bool deletion_ok)
{
Query *parse = root->parse;
int varno = ((RangeTblRef *) jtnode)->rtindex;
* Create a PlannerInfo data structure for this subquery.
*
* NOTE: the next few steps should match the first processing in
- * subquery_planner(). Can we refactor to avoid code duplication, or
+ * subquery_planner(). Can we refactor to avoid code duplication, or
* would that just make things uglier?
*/
subroot = makeNode(PlannerInfo);
subroot->glob = root->glob;
subroot->query_level = root->query_level;
subroot->parent_root = root->parent_root;
+ subroot->plan_params = NIL;
+ subroot->outer_params = NULL;
subroot->planner_cxt = CurrentMemoryContext;
subroot->init_plans = NIL;
subroot->cte_plan_ids = NIL;
+ subroot->multiexpr_params = NIL;
subroot->eq_classes = NIL;
subroot->append_rel_list = NIL;
subroot->rowMarks = NIL;
* pull_up_subqueries' processing is complete for its jointree and
* rangetable.
*
- * Note: we should pass NULL for containing-join info even if we are
- * within an outer join in the upper query; the lower query starts with a
- * clean slate for outer-join semantics. Likewise, we say we aren't
- * handling an appendrel member.
+ * Note: it's okay that the subquery's recursion starts with NULL for
+ * containing-join info, even if we are within an outer join in the upper
+ * query; the lower query starts with a clean slate for outer-join
+ * semantics. Likewise, we needn't pass down appendrel state.
*/
- subquery->jointree = (FromExpr *)
- pull_up_subqueries_recurse(subroot, (Node *) subquery->jointree,
- NULL, NULL, NULL);
+ pull_up_subqueries(subroot);
/*
* Now we must recheck whether the subquery is still simple enough to pull
- * up. If not, abandon processing it.
+ * up. If not, abandon processing it.
*
* We don't really need to recheck all the conditions involved, but it's
* easier just to keep this "if" looking the same as the one in
* pull_up_subqueries_recurse.
*/
- if (is_simple_subquery(subquery, rte, lowest_outer_join) &&
+ if (is_simple_subquery(subquery, rte,
+ lowest_outer_join, deletion_ok) &&
(containing_appendrel == NULL || is_safe_append_member(subquery)))
{
/* good to go */
* Give up, return unmodified RangeTblRef.
*
* Note: The work we just did will be redone when the subquery gets
- * planned on its own. Perhaps we could avoid that by storing the
+ * planned on its own. Perhaps we could avoid that by storing the
* modified subquery back into the rangetable, but I'm not gonna risk
* it now.
*/
return jtnode;
}
+ /*
+ * We must flatten any join alias Vars in the subquery's targetlist,
+ * because pulling up the subquery's subqueries might have changed their
+ * expansions into arbitrary expressions, which could affect
+ * pullup_replace_vars' decisions about whether PlaceHolderVar wrappers
+ * are needed for tlist entries. (Likely it'd be better to do
+ * flatten_join_alias_vars on the whole query tree at some earlier stage,
+ * maybe even in the rewriter; but for now let's just fix this case here.)
+ */
+ subquery->targetList = (List *)
+ flatten_join_alias_vars(subroot, (Node *) subquery->targetList);
+
/*
* Adjust level-0 varnos in subquery so that we can append its rangetable
* to upper query's. We have to fix the subquery's append_rel_list as
/*
* The subquery's targetlist items are now in the appropriate form to
* insert into the top query, but if we are under an outer join then
- * non-nullable items may have to be turned into PlaceHolderVars. If we
- * are dealing with an appendrel member then anything that's not a simple
- * Var has to be turned into a PlaceHolderVar. Set up appropriate context
- * data for pullup_replace_vars.
+ * non-nullable items and lateral references may have to be turned into
+ * PlaceHolderVars. If we are dealing with an appendrel member then
+ * anything that's not a simple Var has to be turned into a
+ * PlaceHolderVar. Set up required context data for pullup_replace_vars.
*/
rvcontext.root = root;
rvcontext.targetlist = subquery->targetList;
rvcontext.target_rte = rte;
+ if (rte->lateral)
+ rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree,
+ true);
+ else /* won't need relids */
+ rvcontext.relids = NULL;
rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
rvcontext.varno = varno;
rvcontext.need_phvs = (lowest_nulling_outer_join != NULL ||
* replace any of the jointree structure. (This'd be a lot cleaner if we
* could use query_tree_mutator.) We have to use PHVs in the targetList,
* returningList, and havingQual, since those are certainly above any
- * outer join. replace_vars_in_jointree tracks its location in the
+ * outer join. replace_vars_in_jointree tracks its location in the
* jointree and uses PHVs or not appropriately.
*/
parse->targetList = (List *)
pullup_replace_vars((Node *) parse->targetList, &rvcontext);
parse->returningList = (List *)
pullup_replace_vars((Node *) parse->returningList, &rvcontext);
+ if (parse->onConflict)
+ parse->onConflict->onConflictSet = (List *)
+ pullup_replace_vars((Node *) parse->onConflict->onConflictSet, &rvcontext);
replace_vars_in_jointree((Node *) parse->jointree, &rvcontext,
lowest_nulling_outer_join);
Assert(parse->setOperations == NULL);
switch (child_rte->rtekind)
{
+ case RTE_RELATION:
+ if (child_rte->tablesample)
+ child_rte->lateral = true;
+ break;
case RTE_SUBQUERY:
case RTE_FUNCTION:
case RTE_VALUES:
child_rte->lateral = true;
break;
- case RTE_RELATION:
case RTE_JOIN:
case RTE_CTE:
/* these can't contain any lateral references */
/*
* Return the adjusted subquery jointree to replace the RangeTblRef entry
- * in parent's jointree.
+ * in parent's jointree; or, if we're flattening a subquery with empty
+ * FROM list, return NULL to signal deletion of the subquery from the
+ * parent jointree (and set hasDeletedRTEs to ensure cleanup later).
*/
+ if (subquery->jointree->fromlist == NIL)
+ {
+ Assert(deletion_ok);
+ Assert(subquery->jointree->quals == NULL);
+ root->hasDeletedRTEs = true;
+ return NULL;
+ }
+
return (Node *) subquery->jointree;
}
* Pull up a single simple UNION ALL subquery.
*
* jtnode is a RangeTblRef that has been identified as a simple UNION ALL
- * subquery by pull_up_subqueries. We pull up the leaf subqueries and
+ * subquery by pull_up_subqueries. We pull up the leaf subqueries and
* build an "append relation" for the union set. The result value is just
* jtnode, since we don't actually need to change the query jointree.
*/
* must build the AppendRelInfo first, because this will modify it.)
* Note that we can pass NULL for containing-join info even if we're
* actually under an outer join, because the child's expressions
- * aren't going to propagate up to the join.
+ * aren't going to propagate up to the join. Also, we ignore the
+ * possibility that pull_up_subqueries_recurse() returns a different
+ * jointree node than what we pass it; if it does, the important thing
+ * is that it replaced the child relid in the AppendRelInfo node.
*/
rtr = makeNode(RangeTblRef);
rtr->rtindex = childRTindex;
(void) pull_up_subqueries_recurse(root, (Node *) rtr,
- NULL, NULL, appinfo);
+ NULL, NULL, appinfo, false);
}
else if (IsA(setOp, SetOperationStmt))
{
* (Note subquery is not necessarily equal to rte->subquery; it could be a
* processed copy of that.)
* lowest_outer_join is the lowest outer join above the subquery, or NULL.
+ * deletion_ok is TRUE if it'd be okay to delete the subquery entirely.
*/
static bool
is_simple_subquery(Query *subquery, RangeTblEntry *rte,
- JoinExpr *lowest_outer_join)
+ JoinExpr *lowest_outer_join,
+ bool deletion_ok)
{
/*
* Let's just make sure it's a valid subselect ...
if (subquery->hasAggs ||
subquery->hasWindowFuncs ||
subquery->groupClause ||
+ subquery->groupingSets ||
subquery->havingQual ||
subquery->sortClause ||
subquery->distinctClause ||
return false;
/*
- * Don't pull up if the RTE represents a security-barrier view; we couldn't
- * prevent information leakage once the RTE's Vars are scattered about in
- * the upper query.
+ * Don't pull up if the RTE represents a security-barrier view; we
+ * couldn't prevent information leakage once the RTE's Vars are scattered
+ * about in the upper query.
*/
if (rte->security_barrier)
return false;
/*
- * If the subquery is LATERAL, and we're below any outer join, and the
- * subquery contains lateral references to rels outside the outer join,
- * don't pull up. Doing so would risk creating outer-join quals that
- * contain references to rels outside the outer join, which is a semantic
- * mess that doesn't seem worth addressing at the moment.
+ * Don't pull up a subquery with an empty jointree, unless it has no quals
+ * and deletion_ok is TRUE and we're not underneath an outer join.
+ *
+ * query_planner() will correctly generate a Result plan for a jointree
+ * that's totally empty, but we can't cope with an empty FromExpr
+ * appearing lower down in a jointree: we identify join rels via baserelid
+ * sets, so we couldn't distinguish a join containing such a FromExpr from
+ * one without it. We can only handle such cases if the place where the
+ * subquery is linked is a FromExpr or inner JOIN that would still be
+ * nonempty after removal of the subquery, so that it's still identifiable
+ * via its contained baserelids. Safe contexts are signaled by
+ * deletion_ok.
+ *
+ * But even in a safe context, we must keep the subquery if it has any
+ * quals, because it's unclear where to put them in the upper query.
+ *
+ * Also, we must forbid pullup if such a subquery is underneath an outer
+ * join, because then we might need to wrap its output columns with
+ * PlaceHolderVars, and the PHVs would then have empty relid sets meaning
+ * we couldn't tell where to evaluate them. (This test is separate from
+ * the deletion_ok flag for possible future expansion: deletion_ok tells
+ * whether the immediate parent site in the jointree could cope, not
+ * whether we'd have PHV issues. It's possible this restriction could be
+ * fixed by letting the PHVs use the relids of the parent jointree item,
+ * but that complication is for another day.)
+ *
+ * Note that deletion of a subquery is also dependent on the check below
+ * that its targetlist contains no set-returning functions. Deletion from
+ * a FROM list or inner JOIN is okay only if the subquery must return
+ * exactly one row.
+ */
+ if (subquery->jointree->fromlist == NIL &&
+ (subquery->jointree->quals != NULL ||
+ !deletion_ok ||
+ lowest_outer_join != NULL))
+ return false;
+
+ /*
+ * If the subquery is LATERAL, check for pullup restrictions from that.
*/
- if (rte->lateral && lowest_outer_join != NULL)
+ if (rte->lateral)
{
- Relids lvarnos = pull_varnos_of_level((Node *) subquery, 1);
- Relids jvarnos = get_relids_in_jointree((Node *) lowest_outer_join,
- true);
+ bool restricted;
+ Relids safe_upper_varnos;
- if (!bms_is_subset(lvarnos, jvarnos))
+ /*
+ * The subquery's WHERE and JOIN/ON quals mustn't contain any lateral
+ * references to rels outside a higher outer join (including the case
+ * where the outer join is within the subquery itself). In such a
+ * case, pulling up would result in a situation where we need to
+ * postpone quals from below an outer join to above it, which is
+ * probably completely wrong and in any case is a complication that
+ * doesn't seem worth addressing at the moment.
+ */
+ if (lowest_outer_join != NULL)
+ {
+ restricted = true;
+ safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join,
+ true);
+ }
+ else
+ {
+ restricted = false;
+ safe_upper_varnos = NULL; /* doesn't matter */
+ }
+
+ if (jointree_contains_lateral_outer_refs((Node *) subquery->jointree,
+ restricted, safe_upper_varnos))
return false;
+
+ /*
+ * If there's an outer join above the LATERAL subquery, also disallow
+ * pullup if the subquery's targetlist has any references to rels
+ * outside the outer join, since these might get pulled into quals
+ * above the subquery (but in or below the outer join) and then lead
+ * to qual-postponement issues similar to the case checked for above.
+ * (We wouldn't need to prevent pullup if no such references appear in
+ * outer-query quals, but we don't have enough info here to check
+ * that. Also, maybe this restriction could be removed if we forced
+ * such refs to be wrapped in PlaceHolderVars, even when they're below
+ * the nearest outer join? But it's a pretty hokey usage, so not
+ * clear this is worth sweating over.)
+ */
+ if (lowest_outer_join != NULL)
+ {
+ Relids lvarnos = pull_varnos_of_level((Node *) subquery->targetList, 1);
+
+ if (!bms_is_subset(lvarnos, safe_upper_varnos))
+ return false;
+ }
}
/*
* Don't pull up a subquery that has any set-returning functions in its
- * targetlist. Otherwise we might well wind up inserting set-returning
+ * targetlist. Otherwise we might well wind up inserting set-returning
* functions into places where they mustn't go, such as quals of higher
- * queries.
+ * queries. This also ensures deletion of an empty jointree is valid.
*/
if (expression_returns_set((Node *) subquery->targetList))
return false;
/*
* Don't pull up a subquery that has any volatile functions in its
- * targetlist. Otherwise we might introduce multiple evaluations of these
+ * targetlist. Otherwise we might introduce multiple evaluations of these
* functions, if they get copied to multiple places in the upper query,
* leading to surprising results. (Note: the PlaceHolderVar mechanism
* doesn't quite guarantee single evaluation; else we could pull up anyway
if (contain_volatile_functions((Node *) subquery->targetList))
return false;
+ return true;
+}
+
+/*
+ * pull_up_simple_values
+ * Pull up a single simple VALUES RTE.
+ *
+ * jtnode is a RangeTblRef that has been identified as a simple VALUES RTE
+ * by pull_up_subqueries. We always return NULL indicating that the RTE
+ * can be deleted entirely (all failure cases should have been detected by
+ * is_simple_values()).
+ *
+ * rte is the RangeTblEntry referenced by jtnode. Because of the limited
+ * possible usage of VALUES RTEs, we do not need the remaining parameters
+ * of pull_up_subqueries_recurse.
+ */
+static Node *
+pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
+{
+ Query *parse = root->parse;
+ int varno = ((RangeTblRef *) jtnode)->rtindex;
+ List *values_list;
+ List *tlist;
+ AttrNumber attrno;
+ pullup_replace_vars_context rvcontext;
+ ListCell *lc;
+
+ Assert(rte->rtekind == RTE_VALUES);
+ Assert(list_length(rte->values_lists) == 1);
+
/*
- * Hack: don't try to pull up a subquery with an empty jointree.
- * query_planner() will correctly generate a Result plan for a jointree
- * that's totally empty, but I don't think the right things happen if an
- * empty FromExpr appears lower down in a jointree. It would pose a
- * problem for the PlaceHolderVar mechanism too, since we'd have no way to
- * identify where to evaluate a PHV coming out of the subquery. Not worth
- * working hard on this, just to collapse SubqueryScan/Result into Result;
- * especially since the SubqueryScan can often be optimized away by
- * setrefs.c anyway.
+ * Need a modifiable copy of the VALUES list to hack on, just in case it's
+ * multiply referenced.
*/
- if (subquery->jointree->fromlist == NIL)
+ values_list = (List *) copyObject(linitial(rte->values_lists));
+
+ /*
+ * The VALUES RTE can't contain any Vars of level zero, let alone any that
+ * are join aliases, so no need to flatten join alias Vars.
+ */
+ Assert(!contain_vars_of_level((Node *) values_list, 0));
+
+ /*
+ * Set up required context data for pullup_replace_vars. In particular,
+ * we have to make the VALUES list look like a subquery targetlist.
+ */
+ tlist = NIL;
+ attrno = 1;
+ foreach(lc, values_list)
+ {
+ tlist = lappend(tlist,
+ makeTargetEntry((Expr *) lfirst(lc),
+ attrno,
+ NULL,
+ false));
+ attrno++;
+ }
+ rvcontext.root = root;
+ rvcontext.targetlist = tlist;
+ rvcontext.target_rte = rte;
+ rvcontext.relids = NULL;
+ rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
+ rvcontext.varno = varno;
+ rvcontext.need_phvs = false;
+ rvcontext.wrap_non_vars = false;
+ /* initialize cache array with indexes 0 .. length(tlist) */
+ rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
+ sizeof(Node *));
+
+ /*
+ * Replace all of the top query's references to the RTE's outputs with
+ * copies of the adjusted VALUES expressions, being careful not to replace
+ * any of the jointree structure. (This'd be a lot cleaner if we could use
+ * query_tree_mutator.) Much of this should be no-ops in the dummy Query
+ * that surrounds a VALUES RTE, but it's not enough code to be worth
+ * removing.
+ */
+ parse->targetList = (List *)
+ pullup_replace_vars((Node *) parse->targetList, &rvcontext);
+ parse->returningList = (List *)
+ pullup_replace_vars((Node *) parse->returningList, &rvcontext);
+ if (parse->onConflict)
+ parse->onConflict->onConflictSet = (List *)
+ pullup_replace_vars((Node *) parse->onConflict->onConflictSet, &rvcontext);
+ replace_vars_in_jointree((Node *) parse->jointree, &rvcontext, NULL);
+ Assert(parse->setOperations == NULL);
+ parse->havingQual = pullup_replace_vars(parse->havingQual, &rvcontext);
+
+ /*
+ * There should be no appendrels to fix, nor any join alias Vars, nor any
+ * outer joins and hence no PlaceHolderVars.
+ */
+ Assert(root->append_rel_list == NIL);
+ Assert(list_length(parse->rtable) == 1);
+ Assert(root->join_info_list == NIL);
+ Assert(root->placeholder_list == NIL);
+
+ /*
+ * Return NULL to signal deletion of the VALUES RTE from the parent
+ * jointree (and set hasDeletedRTEs to ensure cleanup later).
+ */
+ root->hasDeletedRTEs = true;
+ return NULL;
+}
+
+/*
+ * is_simple_values
+ * Check a VALUES RTE in the range table to see if it's simple enough
+ * to pull up into the parent query.
+ *
+ * rte is the RTE_VALUES RangeTblEntry to check.
+ * deletion_ok is TRUE if it'd be okay to delete the VALUES RTE entirely.
+ */
+static bool
+is_simple_values(PlannerInfo *root, RangeTblEntry *rte, bool deletion_ok)
+{
+ Assert(rte->rtekind == RTE_VALUES);
+
+ /*
+ * We can only pull up a VALUES RTE if deletion_ok is TRUE. It's
+ * basically the same case as a sub-select with empty FROM list; see
+ * comments in is_simple_subquery().
+ */
+ if (!deletion_ok)
+ return false;
+
+ /*
+ * Also, there must be exactly one VALUES list, else it's not semantically
+ * correct to delete the VALUES RTE.
+ */
+ if (list_length(rte->values_lists) != 1)
+ return false;
+
+ /*
+ * Because VALUES can't appear under an outer join (or at least, we won't
+ * try to pull it up if it does), we need not worry about LATERAL, nor
+ * about validity of PHVs for the VALUES' outputs.
+ */
+
+ /*
+ * Don't pull up a VALUES that contains any set-returning or volatile
+ * functions. Again, the considerations here are basically identical to
+ * restrictions on a subquery's targetlist.
+ */
+ if (expression_returns_set((Node *) rte->values_lists) ||
+ contain_volatile_functions((Node *) rte->values_lists))
+ return false;
+
+ /*
+ * Do not pull up a VALUES that's not the only RTE in its parent query.
+ * This is actually the only case that the parser will generate at the
+ * moment, and assuming this is true greatly simplifies
+ * pull_up_simple_values().
+ */
+ if (list_length(root->parse->rtable) != 1 ||
+ rte != (RangeTblEntry *) linitial(root->parse->rtable))
return false;
return true;
return true;
}
+/*
+ * jointree_contains_lateral_outer_refs
+ * Check for disallowed lateral references in a jointree's quals
+ *
+ * If restricted is false, all level-1 Vars are allowed (but we still must
+ * search the jointree, since it might contain outer joins below which there
+ * will be restrictions). If restricted is true, return TRUE when any qual
+ * in the jointree contains level-1 Vars coming from outside the rels listed
+ * in safe_upper_varnos.
+ */
+static bool
+jointree_contains_lateral_outer_refs(Node *jtnode, bool restricted,
+ Relids safe_upper_varnos)
+{
+ if (jtnode == NULL)
+ return false;
+ if (IsA(jtnode, RangeTblRef))
+ return false;
+ else if (IsA(jtnode, FromExpr))
+ {
+ FromExpr *f = (FromExpr *) jtnode;
+ ListCell *l;
+
+ /* First, recurse to check child joins */
+ foreach(l, f->fromlist)
+ {
+ if (jointree_contains_lateral_outer_refs(lfirst(l),
+ restricted,
+ safe_upper_varnos))
+ return true;
+ }
+
+ /* Then check the top-level quals */
+ if (restricted &&
+ !bms_is_subset(pull_varnos_of_level(f->quals, 1),
+ safe_upper_varnos))
+ return true;
+ }
+ else if (IsA(jtnode, JoinExpr))
+ {
+ JoinExpr *j = (JoinExpr *) jtnode;
+
+ /*
+ * If this is an outer join, we mustn't allow any upper lateral
+ * references in or below it.
+ */
+ if (j->jointype != JOIN_INNER)
+ {
+ restricted = true;
+ safe_upper_varnos = NULL;
+ }
+
+ /* Check the child joins */
+ if (jointree_contains_lateral_outer_refs(j->larg,
+ restricted,
+ safe_upper_varnos))
+ return true;
+ if (jointree_contains_lateral_outer_refs(j->rarg,
+ restricted,
+ safe_upper_varnos))
+ return true;
+
+ /* Check the JOIN's qual clauses */
+ if (restricted &&
+ !bms_is_subset(pull_varnos_of_level(j->quals, 1),
+ safe_upper_varnos))
+ return true;
+ }
+ else
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
+ return false;
+}
+
/*
* Helper routine for pull_up_subqueries: do pullup_replace_vars on every
* expression in the jointree, without changing the jointree structure itself.
{
switch (rte->rtekind)
{
+ case RTE_RELATION:
+ /* shouldn't be marked LATERAL unless tablesample */
+ Assert(rte->tablesample);
+ rte->tablesample = (TableSampleClause *)
+ pullup_replace_vars((Node *) rte->tablesample,
+ context);
+ break;
case RTE_SUBQUERY:
rte->subquery =
pullup_replace_vars_subquery(rte->subquery,
context);
break;
case RTE_FUNCTION:
- rte->funcexpr =
- pullup_replace_vars(rte->funcexpr,
+ rte->functions = (List *)
+ pullup_replace_vars((Node *) rte->functions,
context);
break;
case RTE_VALUES:
pullup_replace_vars((Node *) rte->values_lists,
context);
break;
- case RTE_RELATION:
case RTE_JOIN:
case RTE_CTE:
/* these shouldn't be marked LATERAL */
/*
* Insert PlaceHolderVar if needed. Notice that we are wrapping one
* PlaceHolderVar around the whole RowExpr, rather than putting one
- * around each element of the row. This is because we need the
+ * around each element of the row. This is because we need the
* expression to yield NULL, not ROW(NULL,NULL,...) when it is forced
* to null by an outer join.
*/
if (newnode && IsA(newnode, Var) &&
((Var *) newnode)->varlevelsup == 0)
{
- /* Simple Vars always escape being wrapped */
- wrap = false;
+ /*
+ * Simple Vars always escape being wrapped, unless they are
+ * lateral references to something outside the subquery being
+ * pulled up. (Even then, we could omit the PlaceHolderVar if
+ * the referenced rel is under the same lowest outer join, but
+ * it doesn't seem worth the trouble to check that.)
+ */
+ if (rcon->target_rte->lateral &&
+ !bms_is_member(((Var *) newnode)->varno, rcon->relids))
+ wrap = true;
+ else
+ wrap = false;
}
else if (newnode && IsA(newnode, PlaceHolderVar) &&
((PlaceHolderVar *) newnode)->phlevelsup == 0)
else
{
/*
- * If it contains a Var of current level, and does not contain
- * any non-strict constructs, then it's certainly nullable so
- * we don't need to insert a PlaceHolderVar.
+ * If it contains a Var of the subquery being pulled up, and
+ * does not contain any non-strict constructs, then it's
+ * certainly nullable so we don't need to insert a
+ * PlaceHolderVar.
*
* This analysis could be tighter: in particular, a non-strict
* construct hidden within a lower-level PlaceHolderVar is not
*
* Note: in future maybe we should insert a PlaceHolderVar
* anyway, if the tlist item is expensive to evaluate?
+ *
+ * For a LATERAL subquery, we have to check the actual var
+ * membership of the node, but if it's non-lateral then any
+ * level-zero var must belong to the subquery.
*/
- if (contain_vars_of_level((Node *) newnode, 0) &&
+ if ((rcon->target_rte->lateral ?
+ bms_overlap(pull_varnos((Node *) newnode), rcon->relids) :
+ contain_vars_of_level((Node *) newnode, 0)) &&
!contain_nonstrict_functions((Node *) newnode))
{
/* No wrap needed */
/*
* Cache it if possible (ie, if the attno is in range, which it
- * probably always should be). We can cache the value even if we
+ * probably always should be). We can cache the value even if we
* decided we didn't need a PHV, since this result will be
* suitable for any request that has need_phvs.
*/
NULL);
}
+/*
+ * pull_up_subqueries_cleanup
+ * Recursively fix up jointree after deletion of some subqueries.
+ *
+ * The jointree now contains some NULL subtrees, which we need to get rid of.
+ * In a FromExpr, just rebuild the child-node list with null entries deleted.
+ * In an inner JOIN, replace the JoinExpr node with a one-child FromExpr.
+ */
+static Node *
+pull_up_subqueries_cleanup(Node *jtnode)
+{
+ Assert(jtnode != NULL);
+ if (IsA(jtnode, RangeTblRef))
+ {
+ /* Nothing to do at leaf nodes. */
+ }
+ else if (IsA(jtnode, FromExpr))
+ {
+ FromExpr *f = (FromExpr *) jtnode;
+ List *newfrom = NIL;
+ ListCell *l;
+
+ foreach(l, f->fromlist)
+ {
+ Node *child = (Node *) lfirst(l);
+
+ if (child == NULL)
+ continue;
+ child = pull_up_subqueries_cleanup(child);
+ newfrom = lappend(newfrom, child);
+ }
+ f->fromlist = newfrom;
+ }
+ else if (IsA(jtnode, JoinExpr))
+ {
+ JoinExpr *j = (JoinExpr *) jtnode;
+
+ if (j->larg)
+ j->larg = pull_up_subqueries_cleanup(j->larg);
+ if (j->rarg)
+ j->rarg = pull_up_subqueries_cleanup(j->rarg);
+ if (j->larg == NULL)
+ {
+ Assert(j->jointype == JOIN_INNER);
+ Assert(j->rarg != NULL);
+ return (Node *) makeFromExpr(list_make1(j->rarg), j->quals);
+ }
+ else if (j->rarg == NULL)
+ {
+ Assert(j->jointype == JOIN_INNER);
+ return (Node *) makeFromExpr(list_make1(j->larg), j->quals);
+ }
+ }
+ else
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
+ return jtnode;
+}
+
/*
* flatten_simple_union_all
*
* If a query's setOperations tree consists entirely of simple UNION ALL
* operations, flatten it into an append relation, which we can process more
- * intelligently than the general setops case. Otherwise, do nothing.
+ * intelligently than the general setops case. Otherwise, do nothing.
*
* In most cases, this can succeed only for a top-level query, because for a
* subquery in FROM, the parent query's invocation of pull_up_subqueries would
* SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL;
* If the join clause is strict for b.y, then only null-extended rows could
* pass the upper WHERE, and we can conclude that what the query is really
- * specifying is an anti-semijoin. We change the join type from JOIN_LEFT
+ * specifying is an anti-semijoin. We change the join type from JOIN_LEFT
* to JOIN_ANTI. The IS NULL clause then becomes redundant, and must be
* removed to prevent bogus selectivity calculations, but we leave it to
* distribute_qual_to_rels to get rid of such clauses.
/*
* See if we can reduce JOIN_LEFT to JOIN_ANTI. This is the case if
* the join's own quals are strict for any var that was forced null by
- * higher qual levels. NOTE: there are other ways that we could
+ * higher qual levels. NOTE: there are other ways that we could
* detect an anti-join, in particular if we were to check whether Vars
* coming from the RHS must be non-null because of table constraints.
* That seems complicated and expensive though (in particular, one
* pulled-up relid, and change them to reference the replacement relid(s).
*
* NOTE: although this has the form of a walker, we cheat and modify the
- * nodes in-place. This should be OK since the tree was copied by
+ * nodes in-place. This should be OK since the tree was copied by
* pullup_replace_vars earlier. Avoid scribbling on the original values of
* the bitmapsets, though, because expression_tree_mutator doesn't copy those.
*/