/* we store the string name because RTE_CTE RTEs need it */
APP_JUMB_STRING(cte->ctename);
+ APP_JUMB(cte->ctematerialized);
JumbleQuery(jstate, castNode(Query, cte->ctequery));
}
break;
-- join in CTE
EXPLAIN (VERBOSE, COSTS OFF)
-WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
+WITH t (c1_1, c1_3, c2_1) AS MATERIALIZED (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------
Limit
Output: t.c1_1, t.c2_1, t.c1_3
(12 rows)
-WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
+WITH t (c1_1, c1_3, c2_1) AS MATERIALIZED (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
c1_1 | c2_1
------+------
101 | 101
SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10 FOR SHARE;
-- join in CTE
EXPLAIN (VERBOSE, COSTS OFF)
-WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
-WITH t (c1_1, c1_3, c2_1) AS (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
+WITH t (c1_1, c1_3, c2_1) AS MATERIALIZED (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
+WITH t (c1_1, c1_3, c2_1) AS MATERIALIZED (SELECT t1.c1, t1.c3, t2.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1)) SELECT c1_1, c2_1 FROM t ORDER BY c1_3, c1_1 OFFSET 100 LIMIT 10;
-- ctid with whole-row reference
EXPLAIN (VERBOSE, COSTS OFF)
SELECT t1.ctid, t1, t2, t1.c1 FROM ft1 t1 JOIN ft2 t2 ON (t1.c1 = t2.c1) ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
</para>
<para>
- A useful property of <literal>WITH</literal> queries is that they are evaluated
- only once per execution of the parent query, even if they are referred to
- more than once by the parent query or sibling <literal>WITH</literal> queries.
+ A useful property of <literal>WITH</literal> queries is that they are
+ normally evaluated only once per execution of the parent query, even if
+ they are referred to more than once by the parent query or
+ sibling <literal>WITH</literal> queries.
Thus, expensive calculations that are needed in multiple places can be
placed within a <literal>WITH</literal> query to avoid redundant work. Another
possible application is to prevent unwanted multiple evaluations of
functions with side-effects.
- However, the other side of this coin is that the optimizer is less able to
- push restrictions from the parent query down into a <literal>WITH</literal> query
- than an ordinary subquery. The <literal>WITH</literal> query will generally be
+ However, the other side of this coin is that the optimizer is not able to
+ push restrictions from the parent query down into a multiply-referenced
+ <literal>WITH</literal> query, since that might affect all uses of the
+ <literal>WITH</literal> query's output when it should affect only one.
+ The multiply-referenced <literal>WITH</literal> query will be
evaluated as written, without suppression of rows that the parent query
might discard afterwards. (But, as mentioned above, evaluation might stop
early if the reference(s) to the query demand only a limited number of
rows.)
</para>
+ <para>
+ However, if a <literal>WITH</literal> query is non-recursive and
+ side-effect-free (that is, it is a <literal>SELECT</literal> containing
+ no volatile functions) then it can be folded into the parent query,
+ allowing joint optimization of the two query levels. By default, this
+ happens if the parent query references the <literal>WITH</literal> query
+ just once, but not if it references the <literal>WITH</literal> query
+ more than once. You can override that decision by
+ specifying <literal>MATERIALIZED</literal> to force separate calculation
+ of the <literal>WITH</literal> query, or by specifying <literal>NOT
+ MATERIALIZED</literal> to force it to be merged into the parent query.
+ The latter choice risks duplicate computation of
+ the <literal>WITH</literal> query, but it can still give a net savings if
+ each usage of the <literal>WITH</literal> query needs only a small part
+ of the <literal>WITH</literal> query's full output.
+ </para>
+
+ <para>
+ A simple example of these rules is
+<programlisting>
+WITH w AS (
+ SELECT * FROM big_table
+)
+SELECT * FROM w WHERE key = 123;
+</programlisting>
+ This <literal>WITH</literal> query will be folded, producing the same
+ execution plan as
+<programlisting>
+SELECT * FROM big_table WHERE key = 123;
+</programlisting>
+ In particular, if there's an index on <structfield>key</structfield>,
+ it will probably be used to fetch just the rows having <literal>key =
+ 123</literal>. On the other hand, in
+<programlisting>
+WITH w AS (
+ SELECT * FROM big_table
+)
+SELECT * FROM w AS w1 JOIN w AS w2 ON w1.key = w2.ref
+WHERE w2.key = 123;
+</programlisting>
+ the <literal>WITH</literal> query will be materialized, producing a
+ temporary copy of <structname>big_table</structname> that is then
+ joined with itself — without benefit of any index. This query
+ will be executed much more efficiently if written as
+<programlisting>
+WITH w AS NOT MATERIALIZED (
+ SELECT * FROM big_table
+)
+SELECT * FROM w AS w1 JOIN w AS w2 ON w1.key = w2.ref
+WHERE w2.key = 123;
+</programlisting>
+ so that the parent query's restrictions can be applied directly
+ to scans of <structname>big_table</structname>.
+ </para>
+
+ <para>
+ An example where <literal>NOT MATERIALIZED</literal> could be
+ undesirable is
+<programlisting>
+WITH w AS (
+ SELECT key, very_expensive_function(val) as f FROM some_table
+)
+SELECT * FROM w AS w1 JOIN w AS w2 ON w1.f = w2.f;
+</programlisting>
+ Here, materialization of the <literal>WITH</literal> query ensures
+ that <function>very_expensive_function</function> is evaluated only
+ once per table row, not twice.
+ </para>
+
<para>
The examples above only show <literal>WITH</literal> being used with
<command>SELECT</command>, but it can be attached in the same way to
<phrase>and <replaceable class="parameter">with_query</replaceable> is:</phrase>
- <replaceable class="parameter">with_query_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ] AS ( <replaceable class="parameter">select</replaceable> | <replaceable class="parameter">values</replaceable> | <replaceable class="parameter">insert</replaceable> | <replaceable class="parameter">update</replaceable> | <replaceable class="parameter">delete</replaceable> )
+ <replaceable class="parameter">with_query_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ] AS [ [ NOT ] MATERIALIZED ] ( <replaceable class="parameter">select</replaceable> | <replaceable class="parameter">values</replaceable> | <replaceable class="parameter">insert</replaceable> | <replaceable class="parameter">update</replaceable> | <replaceable class="parameter">delete</replaceable> )
TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
</synopsis>
These effectively serve as temporary tables that can be referenced
in the <literal>FROM</literal> list. A <literal>WITH</literal> query
that is referenced more than once in <literal>FROM</literal> is
- computed only once.
+ computed only once,
+ unless specified otherwise with <literal>NOT MATERIALIZED</literal>.
(See <xref linkend="sql-with" endterm="sql-with-title"/> below.)
</para>
</listitem>
that are earlier in the <literal>WITH</literal> list.
</para>
+ <para>
+ The primary query and the <literal>WITH</literal> queries are all
+ (notionally) executed at the same time. This implies that the effects of
+ a data-modifying statement in <literal>WITH</literal> cannot be seen from
+ other parts of the query, other than by reading its <literal>RETURNING</literal>
+ output. If two such data-modifying statements attempt to modify the same
+ row, the results are unspecified.
+ </para>
+
<para>
A key property of <literal>WITH</literal> queries is that they
- are evaluated only once per execution of the primary query,
+ are normally evaluated only once per execution of the primary query,
even if the primary query refers to them more than once.
In particular, data-modifying statements are guaranteed to be
executed once and only once, regardless of whether the primary query
</para>
<para>
- The primary query and the <literal>WITH</literal> queries are all
- (notionally) executed at the same time. This implies that the effects of
- a data-modifying statement in <literal>WITH</literal> cannot be seen from
- other parts of the query, other than by reading its <literal>RETURNING</literal>
- output. If two such data-modifying statements attempt to modify the same
- row, the results are unspecified.
+ However, a <literal>WITH</literal> query can be marked
+ <literal>NOT MATERIALIZED</literal> to remove this guarantee. In that
+ case, the <literal>WITH</literal> query can be folded into the primary
+ query much as though it were a simple sub-<literal>SELECT</literal> in
+ the primary query's <literal>FROM</literal> clause. This results in
+ duplicate computations if the primary query refers to
+ that <literal>WITH</literal> query more than once; but if each such use
+ requires only a few rows of the <literal>WITH</literal> query's total
+ output, <literal>NOT MATERIALIZED</literal> can provide a net savings by
+ allowing the queries to be optimized jointly.
+ <literal>NOT MATERIALIZED</literal> is ignored if it is attached to
+ a <literal>WITH</literal> query that is recursive or is not
+ side-effect-free (i.e., is not a plain <literal>SELECT</literal>
+ containing no volatile functions).
+ </para>
+
+ <para>
+ By default, a side-effect-free <literal>WITH</literal> query is folded
+ into the primary query if it is used exactly once in the primary
+ query's <literal>FROM</literal> clause. This allows joint optimization
+ of the two query levels in situations where that should be semantically
+ invisible. However, such folding can be prevented by marking the
+ <literal>WITH</literal> query as <literal>MATERIALIZED</literal>.
+ That might be useful, for example, if the <literal>WITH</literal> query
+ is being used as an optimization fence to prevent the planner from
+ choosing a bad plan.
+ <productname>PostgreSQL</productname> versions before v12 never did
+ such folding, so queries written for older versions might rely on
+ <literal>WITH</literal> to act as an optimization fence.
</para>
<para>
<para>
<literal>ROWS FROM( ... )</literal> is an extension of the SQL standard.
</para>
+
+ <para>
+ The <literal>MATERIALIZED</literal> and <literal>NOT
+ MATERIALIZED</literal> options of <literal>WITH</literal> are extensions
+ of the SQL standard.
+ </para>
</refsect2>
</refsect1>
COPY_STRING_FIELD(ctename);
COPY_NODE_FIELD(aliascolnames);
+ COPY_SCALAR_FIELD(ctematerialized);
COPY_NODE_FIELD(ctequery);
COPY_LOCATION_FIELD(location);
COPY_SCALAR_FIELD(cterecursive);
{
COMPARE_STRING_FIELD(ctename);
COMPARE_NODE_FIELD(aliascolnames);
+ COMPARE_SCALAR_FIELD(ctematerialized);
COMPARE_NODE_FIELD(ctequery);
COMPARE_LOCATION_FIELD(location);
COMPARE_SCALAR_FIELD(cterecursive);
WRITE_STRING_FIELD(ctename);
WRITE_NODE_FIELD(aliascolnames);
+ WRITE_ENUM_FIELD(ctematerialized, CTEMaterialize);
WRITE_NODE_FIELD(ctequery);
WRITE_LOCATION_FIELD(location);
WRITE_BOOL_FIELD(cterecursive);
READ_STRING_FIELD(ctename);
READ_NODE_FIELD(aliascolnames);
+ READ_ENUM_FIELD(ctematerialized, CTEMaterialize);
READ_NODE_FIELD(ctequery);
READ_LOCATION_FIELD(location);
READ_BOOL_FIELD(cterecursive);
root->partColsUpdated = false;
/*
- * If there is a WITH list, process each WITH query and build an initplan
- * SubPlan structure for it.
+ * If there is a WITH list, process each WITH query and either convert it
+ * to RTE_SUBQUERY RTE(s) or build an initplan SubPlan structure for it.
*/
if (parse->cteList)
SS_process_ctes(root);
Bitmapset *paramids; /* Non-local PARAM_EXEC paramids found */
} finalize_primnode_context;
+typedef struct inline_cte_walker_context
+{
+ const char *ctename; /* name and relative level of target CTE */
+ int levelsup;
+ int refcount; /* number of remaining references */
+ Query *ctequery; /* query to substitute */
+} inline_cte_walker_context;
+
static Node *build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
List *plan_params,
static bool subplan_is_hashable(Plan *plan);
static bool testexpr_is_hashable(Node *testexpr);
static bool hash_ok_operator(OpExpr *expr);
+static bool contain_dml(Node *node);
+static bool contain_dml_walker(Node *node, void *context);
+static void inline_cte(PlannerInfo *root, CommonTableExpr *cte);
+static bool inline_cte_walker(Node *node, inline_cte_walker_context *context);
static bool simplify_EXISTS_query(PlannerInfo *root, Query *query);
static Query *convert_EXISTS_to_ANY(PlannerInfo *root, Query *subselect,
Node **testexpr, List **paramIds);
/*
* SS_process_ctes: process a query's WITH list
*
- * We plan each interesting WITH item and convert it to an initplan.
+ * Consider each CTE in the WITH list and either ignore it (if it's an
+ * unreferenced SELECT), "inline" it to create a regular sub-SELECT-in-FROM,
+ * or convert it to an initplan.
+ *
* A side effect is to fill in root->cte_plan_ids with a list that
* parallels root->parse->cteList and provides the subplan ID for
- * each CTE's initplan.
+ * each CTE's initplan, or a dummy ID (-1) if we didn't make an initplan.
*/
void
SS_process_ctes(PlannerInfo *root)
continue;
}
+ /*
+ * Consider inlining the CTE (creating RTE_SUBQUERY RTE(s)) instead of
+ * implementing it as a separately-planned CTE.
+ *
+ * We cannot inline if any of these conditions hold:
+ *
+ * 1. The user said not to (the CTEMaterializeAlways option).
+ *
+ * 2. The CTE is recursive.
+ *
+ * 3. The CTE has side-effects; this includes either not being a plain
+ * SELECT, or containing volatile functions. Inlining might change
+ * the side-effects, which would be bad.
+ *
+ * Otherwise, we have an option whether to inline or not. That should
+ * always be a win if there's just a single reference, but if the CTE
+ * is multiply-referenced then it's unclear: inlining adds duplicate
+ * computations, but the ability to absorb restrictions from the outer
+ * query level could outweigh that. We do not have nearly enough
+ * information at this point to tell whether that's true, so we let
+ * the user express a preference. Our default behavior is to inline
+ * only singly-referenced CTEs, but a CTE marked CTEMaterializeNever
+ * will be inlined even if multiply referenced.
+ */
+ if ((cte->ctematerialized == CTEMaterializeNever ||
+ (cte->ctematerialized == CTEMaterializeDefault &&
+ cte->cterefcount == 1)) &&
+ !cte->cterecursive &&
+ cmdType == CMD_SELECT &&
+ !contain_dml(cte->ctequery) &&
+ !contain_volatile_functions(cte->ctequery))
+ {
+ inline_cte(root, cte);
+ /* Make a dummy entry in cte_plan_ids */
+ root->cte_plan_ids = lappend_int(root->cte_plan_ids, -1);
+ continue;
+ }
+
/*
* Copy the source Query node. Probably not necessary, but let's keep
* this similar to make_subplan.
}
}
+/*
+ * contain_dml: is any subquery not a plain SELECT?
+ *
+ * We reject SELECT FOR UPDATE/SHARE as well as INSERT etc.
+ */
+static bool
+contain_dml(Node *node)
+{
+ return contain_dml_walker(node, NULL);
+}
+
+static bool
+contain_dml_walker(Node *node, void *context)
+{
+ if (node == NULL)
+ return false;
+ if (IsA(node, Query))
+ {
+ Query *query = (Query *) node;
+
+ if (query->commandType != CMD_SELECT ||
+ query->rowMarks != NIL)
+ return true;
+
+ return query_tree_walker(query, contain_dml_walker, context, 0);
+ }
+ return expression_tree_walker(node, contain_dml_walker, context);
+}
+
+/*
+ * inline_cte: convert RTE_CTE references to given CTE into RTE_SUBQUERYs
+ */
+static void
+inline_cte(PlannerInfo *root, CommonTableExpr *cte)
+{
+ struct inline_cte_walker_context context;
+
+ context.ctename = cte->ctename;
+ /* Start at levelsup = -1 because we'll immediately increment it */
+ context.levelsup = -1;
+ context.refcount = cte->cterefcount;
+ context.ctequery = castNode(Query, cte->ctequery);
+
+ (void) inline_cte_walker((Node *) root->parse, &context);
+
+ /* Assert we replaced all references */
+ Assert(context.refcount == 0);
+}
+
+static bool
+inline_cte_walker(Node *node, inline_cte_walker_context *context)
+{
+ if (node == NULL)
+ return false;
+ if (IsA(node, Query))
+ {
+ Query *query = (Query *) node;
+
+ context->levelsup++;
+
+ /*
+ * Visit the query's RTE nodes after their contents; otherwise
+ * query_tree_walker would descend into the newly inlined CTE query,
+ * which we don't want.
+ */
+ (void) query_tree_walker(query, inline_cte_walker, context,
+ QTW_EXAMINE_RTES_AFTER);
+
+ context->levelsup--;
+
+ return false;
+ }
+ else if (IsA(node, RangeTblEntry))
+ {
+ RangeTblEntry *rte = (RangeTblEntry *) node;
+
+ if (rte->rtekind == RTE_CTE &&
+ strcmp(rte->ctename, context->ctename) == 0 &&
+ rte->ctelevelsup == context->levelsup)
+ {
+ /*
+ * Found a reference to replace. Generate a copy of the CTE query
+ * with appropriate level adjustment for outer references (e.g.,
+ * to other CTEs).
+ */
+ Query *newquery = copyObject(context->ctequery);
+
+ if (context->levelsup > 0)
+ IncrementVarSublevelsUp((Node *) newquery, context->levelsup, 1);
+
+ /*
+ * Convert the RTE_CTE RTE into a RTE_SUBQUERY.
+ *
+ * Historically, a FOR UPDATE clause has been treated as extending
+ * into views and subqueries, but not into CTEs. We preserve this
+ * distinction by not trying to push rowmarks into the new
+ * subquery.
+ */
+ rte->rtekind = RTE_SUBQUERY;
+ rte->subquery = newquery;
+ rte->security_barrier = false;
+
+ /* Zero out CTE-specific fields */
+ rte->ctename = NULL;
+ rte->ctelevelsup = 0;
+ rte->self_reference = false;
+ rte->coltypes = NIL;
+ rte->coltypmods = NIL;
+ rte->colcollations = NIL;
+
+ /* Count the number of replacements we've done */
+ context->refcount--;
+ }
+
+ return false;
+ }
+
+ return expression_tree_walker(node, inline_cte_walker, context);
+}
+
+
/*
* convert_ANY_sublink_to_join: try to convert an ANY SubLink to a join
*
%type <list> row explicit_row implicit_row type_list array_expr_list
%type <node> case_expr case_arg when_clause case_default
%type <list> when_clause_list
-%type <ival> sub_type
+%type <ival> sub_type opt_materialized
%type <value> NumericOnly
%type <list> NumericOnly_list
%type <alias> alias_clause opt_alias_clause
| cte_list ',' common_table_expr { $$ = lappend($1, $3); }
;
-common_table_expr: name opt_name_list AS '(' PreparableStmt ')'
+common_table_expr: name opt_name_list AS opt_materialized '(' PreparableStmt ')'
{
CommonTableExpr *n = makeNode(CommonTableExpr);
n->ctename = $1;
n->aliascolnames = $2;
- n->ctequery = $5;
+ n->ctematerialized = $4;
+ n->ctequery = $6;
n->location = @1;
$$ = (Node *) n;
}
;
+opt_materialized:
+ MATERIALIZED { $$ = CTEMaterializeAlways; }
+ | NOT MATERIALIZED { $$ = CTEMaterializeNever; }
+ | /*EMPTY*/ { $$ = CTEMaterializeDefault; }
+ ;
+
opt_with_clause:
with_clause { $$ = $1; }
| /*EMPTY*/ { $$ = NULL; }
/* create common table expression */
cte->ctename = relname;
cte->aliascolnames = aliases;
+ cte->ctematerialized = CTEMaterializeDefault;
cte->ctequery = query;
cte->location = -1;
}
appendStringInfoChar(buf, ')');
}
- appendStringInfoString(buf, " AS (");
+ appendStringInfoString(buf, " AS ");
+ switch (cte->ctematerialized)
+ {
+ case CTEMaterializeDefault:
+ break;
+ case CTEMaterializeAlways:
+ appendStringInfoString(buf, "MATERIALIZED ");
+ break;
+ case CTEMaterializeNever:
+ appendStringInfoString(buf, "NOT MATERIALIZED ");
+ break;
+ }
+ appendStringInfoChar(buf, '(');
if (PRETTY_INDENT(context))
appendContextKeyword(context, "", 0, 0, 0);
get_query_def((Query *) cte->ctequery, buf, context->namespaces, NULL,
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201902112
+#define CATALOG_VERSION_NO 201902161
#endif
*
* We don't currently support the SEARCH or CYCLE clause.
*/
+typedef enum CTEMaterialize
+{
+ CTEMaterializeDefault, /* no option specified */
+ CTEMaterializeAlways, /* MATERIALIZED */
+ CTEMaterializeNever /* NOT MATERIALIZED */
+} CTEMaterialize;
+
typedef struct CommonTableExpr
{
NodeTag type;
char *ctename; /* query name (never qualified) */
List *aliascolnames; /* optional list of column names */
+ CTEMaterialize ctematerialized; /* is this an optimization fence? */
/* SelectStmt/InsertStmt/etc before parse analysis, Query afterwards: */
Node *ctequery; /* the CTE's subquery */
int location; /* token location, or -1 if unknown */
Filter: (((a % 2) = 0) AND f_leak(b))
(2 rows)
-PREPARE plancache_test2 AS WITH q AS (SELECT * FROM z1 WHERE f_leak(b)) SELECT * FROM q,z2;
+PREPARE plancache_test2 AS WITH q AS MATERIALIZED (SELECT * FROM z1 WHERE f_leak(b)) SELECT * FROM q,z2;
EXPLAIN (COSTS OFF) EXECUTE plancache_test2;
QUERY PLAN
-------------------------------------------------
-> Seq Scan on z2
(7 rows)
-PREPARE plancache_test3 AS WITH q AS (SELECT * FROM z2) SELECT * FROM q,z1 WHERE f_leak(z1.b);
+PREPARE plancache_test3 AS WITH q AS MATERIALIZED (SELECT * FROM z2) SELECT * FROM q,z1 WHERE f_leak(z1.b);
EXPLAIN (COSTS OFF) EXECUTE plancache_test3;
QUERY PLAN
-----------------------------------------------------
GRANT ALL ON t1 TO regress_rls_bob;
INSERT INTO t1 (SELECT x, md5(x::text) FROM generate_series(0,20) x);
SET SESSION AUTHORIZATION regress_rls_bob;
-WITH cte1 AS (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
+WITH cte1 AS MATERIALIZED (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
NOTICE: f_leak => cfcd208495d565ef66e7dff9f98764da
NOTICE: f_leak => c81e728d9d4c2f636f067f89cc14862c
NOTICE: f_leak => a87ff679a2f3e71d9181a67b7542122c
20 | 98f13708210194c475687be6106a3b84
(11 rows)
-EXPLAIN (COSTS OFF) WITH cte1 AS (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
+EXPLAIN (COSTS OFF)
+WITH cte1 AS MATERIALIZED (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
QUERY PLAN
-------------------------------------------------
CTE Scan on cte1
(6 rows)
explain (verbose, costs off)
-with r(a,b) as
+with r(a,b) as materialized
(values (1,row(1,2)), (1,row(null,null)), (1,null),
(null,row(1,2)), (null,row(null,null)), (null,null) )
select r, r is null as isnull, r is not null as isnotnull from r;
Output: "*VALUES*".column1, "*VALUES*".column2
(5 rows)
-with r(a,b) as
+with r(a,b) as materialized
(values (1,row(1,2)), (1,row(null,null)), (1,null),
(null,row(1,2)), (null,row(null,null)), (null,null) )
select r, r is null as isnull, r is not null as isnotnull from r;
(5 rows)
-- ensure upserting into a rule, with a CTE (different offsets!) works
-WITH data(hat_name, hat_color) AS (
+WITH data(hat_name, hat_color) AS MATERIALIZED (
VALUES ('h8', 'green'),
('h9', 'blue'),
('h7', 'forbidden')
h9 | blue
(2 rows)
-EXPLAIN (costs off) WITH data(hat_name, hat_color) AS (
+EXPLAIN (costs off)
+WITH data(hat_name, hat_color) AS MATERIALIZED (
VALUES ('h8', 'green'),
('h9', 'blue'),
('h7', 'forbidden')
(2 rows)
commit;
+--
+-- Tests for CTE inlining behavior
+--
+-- Basic subquery that can be inlined
+explain (verbose, costs off)
+with x as (select * from (select f1 from subselect_tbl) ss)
+select * from x where f1 = 1;
+ QUERY PLAN
+----------------------------------
+ Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1
+ Filter: (subselect_tbl.f1 = 1)
+(3 rows)
+
+-- Explicitly request materialization
+explain (verbose, costs off)
+with x as materialized (select * from (select f1 from subselect_tbl) ss)
+select * from x where f1 = 1;
+ QUERY PLAN
+------------------------------------------
+ CTE Scan on x
+ Output: x.f1
+ Filter: (x.f1 = 1)
+ CTE x
+ -> Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1
+(6 rows)
+
+-- Stable functions are safe to inline
+explain (verbose, costs off)
+with x as (select * from (select f1, now() from subselect_tbl) ss)
+select * from x where f1 = 1;
+ QUERY PLAN
+-----------------------------------
+ Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, now()
+ Filter: (subselect_tbl.f1 = 1)
+(3 rows)
+
+-- Volatile functions prevent inlining
+explain (verbose, costs off)
+with x as (select * from (select f1, random() from subselect_tbl) ss)
+select * from x where f1 = 1;
+ QUERY PLAN
+----------------------------------------------
+ CTE Scan on x
+ Output: x.f1, x.random
+ Filter: (x.f1 = 1)
+ CTE x
+ -> Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, random()
+(6 rows)
+
+-- SELECT FOR UPDATE cannot be inlined
+explain (verbose, costs off)
+with x as (select * from (select f1 from subselect_tbl for update) ss)
+select * from x where f1 = 1;
+ QUERY PLAN
+--------------------------------------------------------------------
+ CTE Scan on x
+ Output: x.f1
+ Filter: (x.f1 = 1)
+ CTE x
+ -> Subquery Scan on ss
+ Output: ss.f1
+ -> LockRows
+ Output: subselect_tbl.f1, subselect_tbl.ctid
+ -> Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, subselect_tbl.ctid
+(10 rows)
+
+-- Multiply-referenced CTEs are inlined only when requested
+explain (verbose, costs off)
+with x as (select * from (select f1, now() as n from subselect_tbl) ss)
+select * from x, x x2 where x.n = x2.n;
+ QUERY PLAN
+-------------------------------------------
+ Merge Join
+ Output: x.f1, x.n, x2.f1, x2.n
+ Merge Cond: (x.n = x2.n)
+ CTE x
+ -> Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, now()
+ -> Sort
+ Output: x.f1, x.n
+ Sort Key: x.n
+ -> CTE Scan on x
+ Output: x.f1, x.n
+ -> Sort
+ Output: x2.f1, x2.n
+ Sort Key: x2.n
+ -> CTE Scan on x x2
+ Output: x2.f1, x2.n
+(16 rows)
+
+explain (verbose, costs off)
+with x as not materialized (select * from (select f1, now() as n from subselect_tbl) ss)
+select * from x, x x2 where x.n = x2.n;
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Result
+ Output: subselect_tbl.f1, now(), subselect_tbl_1.f1, now()
+ One-Time Filter: (now() = now())
+ -> Nested Loop
+ Output: subselect_tbl.f1, subselect_tbl_1.f1
+ -> Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, subselect_tbl.f2, subselect_tbl.f3
+ -> Materialize
+ Output: subselect_tbl_1.f1
+ -> Seq Scan on public.subselect_tbl subselect_tbl_1
+ Output: subselect_tbl_1.f1
+(11 rows)
+
+-- Check handling of outer references
+explain (verbose, costs off)
+with x as (select * from int4_tbl)
+select * from (with y as (select * from x) select * from y) ss;
+ QUERY PLAN
+-----------------------------
+ Seq Scan on public.int4_tbl
+ Output: int4_tbl.f1
+(2 rows)
+
+explain (verbose, costs off)
+with x as materialized (select * from int4_tbl)
+select * from (with y as (select * from x) select * from y) ss;
+ QUERY PLAN
+-------------------------------------
+ CTE Scan on x
+ Output: x.f1
+ CTE x
+ -> Seq Scan on public.int4_tbl
+ Output: int4_tbl.f1
+(5 rows)
+
+-- Ensure that we inline the currect CTE when there are
+-- multiple CTEs with the same name
+explain (verbose, costs off)
+with x as (select 1 as y)
+select * from (with x as (select 2 as y) select * from x) ss;
+ QUERY PLAN
+-------------
+ Result
+ Output: 2
+(2 rows)
+
+-- Row marks are not pushed into CTEs
+explain (verbose, costs off)
+with x as (select * from subselect_tbl)
+select * from x for update;
+ QUERY PLAN
+----------------------------------------------------------------
+ Seq Scan on public.subselect_tbl
+ Output: subselect_tbl.f1, subselect_tbl.f2, subselect_tbl.f3
+(2 rows)
+
PREPARE plancache_test AS SELECT * FROM z1 WHERE f_leak(b);
EXPLAIN (COSTS OFF) EXECUTE plancache_test;
-PREPARE plancache_test2 AS WITH q AS (SELECT * FROM z1 WHERE f_leak(b)) SELECT * FROM q,z2;
+PREPARE plancache_test2 AS WITH q AS MATERIALIZED (SELECT * FROM z1 WHERE f_leak(b)) SELECT * FROM q,z2;
EXPLAIN (COSTS OFF) EXECUTE plancache_test2;
-PREPARE plancache_test3 AS WITH q AS (SELECT * FROM z2) SELECT * FROM q,z1 WHERE f_leak(z1.b);
+PREPARE plancache_test3 AS WITH q AS MATERIALIZED (SELECT * FROM z2) SELECT * FROM q,z1 WHERE f_leak(z1.b);
EXPLAIN (COSTS OFF) EXECUTE plancache_test3;
SET ROLE regress_rls_group1;
SET SESSION AUTHORIZATION regress_rls_bob;
-WITH cte1 AS (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
-EXPLAIN (COSTS OFF) WITH cte1 AS (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
+WITH cte1 AS MATERIALIZED (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
+EXPLAIN (COSTS OFF)
+WITH cte1 AS MATERIALIZED (SELECT * FROM t1 WHERE f_leak(b)) SELECT * FROM cte1;
WITH cte1 AS (UPDATE t1 SET a = a + 1 RETURNING *) SELECT * FROM cte1; --fail
WITH cte1 AS (UPDATE t1 SET a = a RETURNING *) SELECT * FROM cte1; --ok
(null,row(1,2)), (null,row(null,null)), (null,null) ) r(a,b);
explain (verbose, costs off)
-with r(a,b) as
+with r(a,b) as materialized
(values (1,row(1,2)), (1,row(null,null)), (1,null),
(null,row(1,2)), (null,row(null,null)), (null,null) )
select r, r is null as isnull, r is not null as isnotnull from r;
-with r(a,b) as
+with r(a,b) as materialized
(values (1,row(1,2)), (1,row(null,null)), (1,null),
(null,row(1,2)), (null,row(null,null)), (null,null) )
select r, r is null as isnull, r is not null as isnotnull from r;
explain (costs off) INSERT INTO hats VALUES ('h8', 'forbidden') RETURNING *;
-- ensure upserting into a rule, with a CTE (different offsets!) works
-WITH data(hat_name, hat_color) AS (
+WITH data(hat_name, hat_color) AS MATERIALIZED (
VALUES ('h8', 'green'),
('h9', 'blue'),
('h7', 'forbidden')
INSERT INTO hats
SELECT * FROM data
RETURNING *;
-EXPLAIN (costs off) WITH data(hat_name, hat_color) AS (
+EXPLAIN (costs off)
+WITH data(hat_name, hat_color) AS MATERIALIZED (
VALUES ('h8', 'green'),
('h9', 'blue'),
('h7', 'forbidden')
fetch backward all in c1;
commit;
+
+--
+-- Tests for CTE inlining behavior
+--
+
+-- Basic subquery that can be inlined
+explain (verbose, costs off)
+with x as (select * from (select f1 from subselect_tbl) ss)
+select * from x where f1 = 1;
+
+-- Explicitly request materialization
+explain (verbose, costs off)
+with x as materialized (select * from (select f1 from subselect_tbl) ss)
+select * from x where f1 = 1;
+
+-- Stable functions are safe to inline
+explain (verbose, costs off)
+with x as (select * from (select f1, now() from subselect_tbl) ss)
+select * from x where f1 = 1;
+
+-- Volatile functions prevent inlining
+explain (verbose, costs off)
+with x as (select * from (select f1, random() from subselect_tbl) ss)
+select * from x where f1 = 1;
+
+-- SELECT FOR UPDATE cannot be inlined
+explain (verbose, costs off)
+with x as (select * from (select f1 from subselect_tbl for update) ss)
+select * from x where f1 = 1;
+
+-- Multiply-referenced CTEs are inlined only when requested
+explain (verbose, costs off)
+with x as (select * from (select f1, now() as n from subselect_tbl) ss)
+select * from x, x x2 where x.n = x2.n;
+
+explain (verbose, costs off)
+with x as not materialized (select * from (select f1, now() as n from subselect_tbl) ss)
+select * from x, x x2 where x.n = x2.n;
+
+-- Check handling of outer references
+explain (verbose, costs off)
+with x as (select * from int4_tbl)
+select * from (with y as (select * from x) select * from y) ss;
+
+explain (verbose, costs off)
+with x as materialized (select * from int4_tbl)
+select * from (with y as (select * from x) select * from y) ss;
+
+-- Ensure that we inline the currect CTE when there are
+-- multiple CTEs with the same name
+explain (verbose, costs off)
+with x as (select 1 as y)
+select * from (with x as (select 2 as y) select * from x) ss;
+
+-- Row marks are not pushed into CTEs
+explain (verbose, costs off)
+with x as (select * from subselect_tbl)
+select * from x for update;
projects / postgresql / commitdiff