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);
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,
* 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);
+ NULL,
+ true);
j->rarg = pull_up_subqueries_recurse(root, j->rarg,
lowest_outer_join,
lowest_nulling_outer_join,
- NULL);
+ NULL,
+ j->larg != NULL);
break;
case JOIN_LEFT:
case JOIN_SEMI:
j->larg = pull_up_subqueries_recurse(root, j->larg,
j,
lowest_nulling_outer_join,
- NULL);
+ 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);
+ NULL,
+ false);
break;
default:
elog(ERROR, "unrecognized join type: %d",
*
* 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.
+ * 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;
* 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
* 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 */
/*
* 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;
}
* 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 (rte->security_barrier)
return false;
+ /*
+ * Don't pull up a subquery with an empty jointree, unless it has no quals
+ * and deletion_ok is TRUE. 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. This would for example break the
+ * PlaceHolderVar mechanism, since we'd have no way to identify where to
+ * evaluate a PHV coming out of the subquery. 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. (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 || !deletion_ok))
+ return false;
+
/*
* If the subquery is LATERAL, check for pullup restrictions from that.
*/
* Don't pull up a subquery that has any set-returning functions in its
* 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;
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);
+
/*
- * Don't pull up a subquery with an empty jointree. 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. This
- * would for example break the PlaceHolderVar mechanism, 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);
+ 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->lateral_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.
+ */
+
+ /*
+ * 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;
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
projects / postgresql / commitdiff