diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1da7dfb..33a6009 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -6048,6 +6048,23 @@ SET XML OPTION { DOCUMENT | CONTENT };
+
+ max_recursion_depth (integer)
+
+ max_recursion_depth configuration parameter
+
+
+
+
+ Sets the maximum recursion depth in WITH Queries (Common Table Expressions).
+ The default value is 0 and it means no limit for recursion depth (infinite loop is possible).
+ When max_recursion_depth > 0 and the recursion level of query exceeds specified value
+ then execution of query interrupts with error message.
+ See for more information.
+
+
+
+
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml
index ab49bd7..80a63c8 100644
--- a/doc/src/sgml/queries.sgml
+++ b/doc/src/sgml/queries.sgml
@@ -2216,6 +2216,46 @@ SELECT n FROM t LIMIT 100;
In each case it effectively provides temporary table(s) that can
be referred to in the main command.
+
+
+
+ Also it is possible to limit the number of returning rows by setting parameter
+ max_recursion_depth in the postgresql.conf file.
+ See for more information.
+
+
+
+
+ Another way to set max_recursion_depth is SET max_recursion_depth command in psql.
+
+
+postgres=# show max_recursion_depth;
+LOG: statement: show max_recursion_depth;
+ max_recursion_depth
+---------------------
+ 0
+(1 row)
+
+postgres=# set max_recursion_depth = 5;
+LOG: statement: set max_recursion_depth = 5;
+SET
+postgres=# show max_recursion_depth;
+LOG: statement: show max_recursion_depth;
+ max_recursion_depth
+---------------------
+ 5
+(1 row)
+
+ When max_recursion_depth > 0 and the recursion level of query exceeds specified value
+ then execution of query interrupts with error message like this:
+
+
+ ERROR: The statement terminated. The maximum recursion depth 5 has been exhausted before statement completion.
+
+
+
+
+
diff --git a/src/backend/executor/nodeRecursiveunion.c b/src/backend/executor/nodeRecursiveunion.c
index 8df1639..c616250 100644
--- a/src/backend/executor/nodeRecursiveunion.c
+++ b/src/backend/executor/nodeRecursiveunion.c
@@ -110,6 +110,13 @@ ExecRecursiveUnion(RecursiveUnionState *node)
/* 2. Execute recursive term */
for (;;)
{
+ if ((with_recursive_limit > 0) && (node->ps.recursion_cnt >= with_recursive_limit))
+ {
+ ereport(ERROR,
+ (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+ errmsg("The statement terminated. The maximum recursion depth %d has been exhausted before statement completion.", with_recursive_limit)));
+ break;
+ }
slot = ExecProcNode(innerPlan);
if (TupIsNull(slot))
{
@@ -132,6 +139,9 @@ ExecRecursiveUnion(RecursiveUnionState *node)
innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
plan->wtParam);
+ /* go to the next recursion level */
+ node->ps.recursion_cnt++;
+
/* and continue fetching from recursive term */
continue;
}
@@ -261,6 +271,11 @@ ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
build_hash_table(rustate);
}
+ /*
+ * Init recursion depth counter.
+ */
+ rustate->ps.recursion_cnt=0;
+
return rustate;
}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 230c5cc..c39e8ca 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -112,6 +112,9 @@ extern char *temp_tablespaces;
extern bool ignore_checksum_failure;
extern bool synchronize_seqscans;
+/* Parameters for controlling recursive depth */
+int with_recursive_limit;
+
#ifdef TRACE_SYNCSCAN
extern bool trace_syncscan;
#endif
@@ -2669,6 +2672,18 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {
+ {"max_recursion_depth", PGC_USERSET, CUSTOM_OPTIONS,
+ gettext_noop("Sets the maximum recursion depth in WITH RECURSIVE "
+ "and other CTE operations."),
+ gettext_noop("Sets the maximum recursion depth in WITH RECURSIVE "
+ "and other CTE operations.")
+ },
+ &with_recursive_limit,
+ 0, 0, INT_MAX,
+ NULL, NULL, NULL
+ },
+
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 06dfc06..e5e8e53 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -527,6 +527,7 @@
#xmlbinary = 'base64'
#xmloption = 'content'
#gin_pending_list_limit = 4MB
+#max_recursion_depth = 0 # max depth for CTE range 0-INT_MAX, 0 means infinite
# - Locale and Formatting -
diff --git a/src/include/executor/nodeRecursiveunion.h b/src/include/executor/nodeRecursiveunion.h
index 52cacd8..036857f 100644
--- a/src/include/executor/nodeRecursiveunion.h
+++ b/src/include/executor/nodeRecursiveunion.h
@@ -20,5 +20,7 @@ extern RecursiveUnionState *ExecInitRecursiveUnion(RecursiveUnion *node, EState
extern TupleTableSlot *ExecRecursiveUnion(RecursiveUnionState *node);
extern void ExecEndRecursiveUnion(RecursiveUnionState *node);
extern void ExecReScanRecursiveUnion(RecursiveUnionState *node);
+/* Parameters for controlling recursive depth */
+extern int with_recursive_limit;
#endif /* NODERECURSIVEUNION_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index db5bd7f..eb82c5d 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1059,6 +1059,7 @@ typedef struct PlanState
ProjectionInfo *ps_ProjInfo; /* info for doing tuple projection */
bool ps_TupFromTlist;/* state flag for processing set-valued
* functions in targetlist */
+ int recursion_cnt; /* counter for recursion depth */
} PlanState;
/* ----------------
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 2c9226c..d42ce09 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -2256,3 +2256,66 @@ with ordinality as (select 1 as x) select * from ordinality;
1
(1 row)
+--
+-- RECURSION DEPTH
+-- Check the max_recursion_depth parameter
+--
+CREATE TABLE test_max_recurs ( parent integer, child integer);
+INSERT INTO test_max_recurs (parent, child) VALUES
+-- infinite recursion
+(1,2), (2,1),
+--just too deep path
+(100,101), (101,102), (102,103), (103,104), (104,105), (105,0),
+--good
+(200,201), (201,202), (202,203), (203,204), (204,0),
+-- tree-like too much number of nodes
+(300,311), (311,312), (312,0), (300,321), (321,322), (322,0),
+-- tree-like good
+(400,411), (411,412), (412,0), (400,421), (421,0);
+SET max_recursion_depth to 5;
+SHOW max_recursion_depth;
+ max_recursion_depth
+---------------------
+ 5
+(1 row)
+
+-- Stress test for max_recursion_depth parameter
+WITH RECURSIVE g(id)
+AS (SELECT 1::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+ERROR: The statement terminated. The maximum recursion depth 5 has been exhausted before statement completion.
+WITH RECURSIVE g(id)
+AS (SELECT 100::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+ERROR: The statement terminated. The maximum recursion depth 5 has been exhausted before statement completion.
+WITH RECURSIVE g(id)
+AS (SELECT 200::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+ERROR: The statement terminated. The maximum recursion depth 5 has been exhausted before statement completion.
+WITH RECURSIVE g(id)
+AS (SELECT 300::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+ id
+-----
+ 300
+ 311
+ 321
+ 312
+ 322
+ 0
+ 0
+(7 rows)
+
+WITH RECURSIVE g(id)
+AS (SELECT 400::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+ id
+-----
+ 400
+ 411
+ 421
+ 412
+ 0
+ 0
+(6 rows)
+
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index 3fd55f9..cede610 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -1018,3 +1018,45 @@ DROP RULE y_rule ON y;
create table foo (with baz); -- fail, WITH is a reserved word
create table foo (with ordinality); -- fail, WITH is a reserved word
with ordinality as (select 1 as x) select * from ordinality;
+
+--
+-- RECURSION DEPTH
+-- Check the max_recursion_depth parameter
+--
+CREATE TABLE test_max_recurs ( parent integer, child integer);
+
+INSERT INTO test_max_recurs (parent, child) VALUES
+-- infinite recursion
+(1,2), (2,1),
+--just too deep path
+(100,101), (101,102), (102,103), (103,104), (104,105), (105,0),
+--good
+(200,201), (201,202), (202,203), (203,204), (204,0),
+-- tree-like too much number of nodes
+(300,311), (311,312), (312,0), (300,321), (321,322), (322,0),
+-- tree-like good
+(400,411), (411,412), (412,0), (400,421), (421,0);
+
+SET max_recursion_depth to 5;
+SHOW max_recursion_depth;
+
+-- Stress test for max_recursion_depth parameter
+WITH RECURSIVE g(id)
+AS (SELECT 1::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+
+WITH RECURSIVE g(id)
+AS (SELECT 100::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+
+WITH RECURSIVE g(id)
+AS (SELECT 200::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+
+WITH RECURSIVE g(id)
+AS (SELECT 300::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;
+
+WITH RECURSIVE g(id)
+AS (SELECT 400::int UNION ALL SELECT child AS id from test_max_recurs tt, g where tt.parent=g.id)
+SELECT * FROM g;