Subject: [PATCH v8] Add assorted partition reporting functions

From: amit <[email-masked]>
Date: Tue, 16 Jan 2018 19:02:13 +0900

---
 doc/src/sgml/func.sgml                       |  89 ++++++++++
 src/backend/catalog/partition.c              | 244 ++++++++++++++++++++++++++-
 src/backend/utils/cache/lsyscache.c          |  22 +++
 src/include/catalog/pg_proc.dat              |  48 ++++++
 src/include/utils/lsyscache.h                |   1 +
 src/test/regress/expected/partition_info.out | 204 ++++++++++++++++++++++
 src/test/regress/parallel_schedule           |   2 +-
 src/test/regress/serial_schedule             |   1 +
 src/test/regress/sql/partition_info.sql      |  91 ++++++++++
 9 files changed, 697 insertions(+), 5 deletions(-)
 create mode 100644 src/test/regress/expected/partition_info.out
 create mode 100644 src/test/regress/sql/partition_info.sql

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index edc9be92a6..326f4dbe58 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -19995,6 +19995,95 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
     The function returns the number of new collation objects it created.
    </para>
 
+   <table id="functions-info-partition">
+    <title>Partitioning Information Functions</title>
+    <tgroup cols="3">
+     <thead>
+      <row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row>
+     </thead>
+
+     <tbody> 
+      <row>
+       <entry><literal><function>pg_partition_parent(<type>regclass</type>)</function></literal></entry>
+       <entry><type>regclass</type></entry>
+       <entry>get parent if table is a partition, <literal>NULL</literal> otherwise</entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_root_parent(<type>regclass</type>)</function></literal></entry>
+       <entry><type>regclass</type></entry>
+       <entry>get topmost parent of a partition within partition tree</entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_level(<type>regclass</type>, <type>regclass</type>)</function></literal></entry>
+       <entry><type>regclass</type></entry>
+       <entry>get level of a partition within partition tree with respect to given parent</entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_level(<type>regclass</type>)</function></literal></entry>
+       <entry><type>regclass</type></entry>
+       <entry>get level of a partition within partition tree with respect to topmost root parent</entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_children(<type>regclass</type>, <type>bool</type>)</function></literal></entry>
+       <entry><type>setof regclass</type></entry>
+       <entry>
+        get partitions of a table; only immediate partitions are returned,
+        unless all tables in the partition tree, including itself and
+        partitions of lower levels, are requested by passing
+        <literal>true</literal> for second argument
+       </entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_children(<type>regclass</type>)</function></literal></entry>
+       <entry><type>setof regclass</type></entry>
+       <entry>Shorthand for <literal>pg_partition_children(..., false)</literal></entry>
+      </row>
+      <row>
+       <entry><literal><function>pg_partition_leaf_children(<type>regclass</type>)</function></literal></entry>
+       <entry><type>setof regclass</type></entry>
+       <entry>get all leaf partitions of a given table</entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+   <para>
+    If the table passed to <function>pg_partition_root_parent</function> is not
+    a partition, it is returned as the its own root parent.  If the table
+    passed for the second argument of <function>pg_partition_level</function>
+    is not same as the first argument or not an ancestor of the table in the
+    first argument, -1 is returned as the result.
+   </para>
+
+   <para>
+    To check the total size of the data contained in
+    <structname>measurement</structname> table described in
+    <xref linkend="ddl-partitioning-declarative-example"/>, use the following
+    query:
+   </para>
+
+<programlisting>
+select pg_size_pretty(sum(pg_relation_size(p))) as total_size from pg_partition_children('measurement', true) p;
+ total_size 
+------------
+ 24 kB
+(1 row)
+</programlisting>
+
+   <para>
+    One could have used <function>pg_partition_leaf_children</function> in
+    this case and got the same result as shown below:
+   </para>
+
+<programlisting>
+select pg_size_pretty(sum(pg_relation_size(p))) as total_size from pg_partition_leaf_children('measurement') p;
+ total_size 
+------------
+ 24 kB
+(1 row)
+</programlisting>
+
+
   </sect2>
 
   <sect2 id="functions-admin-index">
diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 558022647c..d90aaf8bb8 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -23,13 +23,16 @@
 #include "catalog/partition.h"
 #include "catalog/pg_inherits.h"
 #include "catalog/pg_partitioned_table.h"
+#include "funcapi.h"
 #include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
 #include "optimizer/prep.h"
 #include "optimizer/var.h"
 #include "partitioning/partbounds.h"
 #include "rewrite/rewriteManip.h"
+#include "utils/builtins.h"
 #include "utils/fmgroids.h"
+#include "utils/lsyscache.h"
 #include "utils/partcache.h"
 #include "utils/rel.h"
 #include "utils/syscache.h"
@@ -38,16 +41,14 @@
 static Oid	get_partition_parent_worker(Relation inhRel, Oid relid);
 static void get_partition_ancestors_worker(Relation inhRel, Oid relid,
 							   List **ancestors);
+static Oid	get_partition_root_parent(Oid relid);
+static List *get_partition_tree_leaf_tables(Oid relid);
 
 /*
  * get_partition_parent
  *		Obtain direct parent of given relation
  *
  * Returns inheritance parent of a partition by scanning pg_inherits
- *
- * Note: Because this function assumes that the relation whose OID is passed
- * as an argument will have precisely one parent, it should only be called
- * when it is known that the relation is a partition.
  */
 Oid
 get_partition_parent(Oid relid)
@@ -55,6 +56,9 @@ get_partition_parent(Oid relid)
 	Relation	catalogRelation;
 	Oid			result;
 
+	if (!get_rel_relispartition(relid))
+		return InvalidOid;
+
 	catalogRelation = heap_open(InheritsRelationId, AccessShareLock);
 
 	result = get_partition_parent_worker(catalogRelation, relid);
@@ -71,6 +75,10 @@ get_partition_parent(Oid relid)
  * get_partition_parent_worker
  *		Scan the pg_inherits relation to return the OID of the parent of the
  *		given relation
+ *
+ * Note: Because this function assumes that the relation whose OID is passed
+ * as an argument will have precisely one parent, it should only be called
+ * when it is known that the relation is a partition.
  */
 static Oid
 get_partition_parent_worker(Relation inhRel, Oid relid)
@@ -148,6 +156,28 @@ get_partition_ancestors_worker(Relation inhRel, Oid relid, List **ancestors)
 }
 
 /*
+ * get_partition_root_parent
+ *
+ * Returns root inheritance ancestor of a partition.
+ */
+Oid
+get_partition_root_parent(Oid relid)
+{
+	List	   *ancestors;
+	Oid			result;
+
+	if (!get_rel_relispartition(relid))
+		return InvalidOid;
+
+	ancestors = get_partition_ancestors(relid);
+	result = llast_oid(ancestors);
+	Assert(!get_rel_relispartition(result));
+	list_free(ancestors);
+
+	return result;
+}
+
+/*
  * map_partition_varattnos - maps varattno of any Vars in expr from the
  * attno's of 'from_rel' to the attno's of 'to_rel' partition, each of which
  * may be either a leaf partition or a partitioned table, but both of which
@@ -357,3 +387,209 @@ get_proposed_default_constraint(List *new_part_constraints)
 
 	return make_ands_implicit(defPartConstraint);
 }
+
+/*
+ * SQL wrapper around get_partition_root_parent().
+ */
+Datum
+pg_partition_root_parent(PG_FUNCTION_ARGS)
+{
+	Oid		reloid = PG_GETARG_OID(0);
+	Oid		rootoid;
+
+	rootoid = get_partition_root_parent(reloid);
+
+	/*
+	 * If the relation is actually a partition, 'rootoid' has been set to the
+	 * OID of the root table in the partition tree.
+	 */
+	if (OidIsValid(rootoid))
+		PG_RETURN_OID(rootoid);
+
+	/*
+	 * Otherwise, the table's not a partition.  That is, it's either the root
+	 * table in a partition tree or a standalone table that's not part of any
+	 * partition tree.  In any case, return the table OID itself as the
+	 * result.
+	 */
+	PG_RETURN_OID(reloid);
+}
+
+/*
+ * SQL wrapper around get_partition_parent().
+ */
+Datum
+pg_partition_parent(PG_FUNCTION_ARGS)
+{
+	Oid		reloid = PG_GETARG_OID(0);
+	Oid		parentoid;
+
+	parentoid = get_partition_parent(reloid);
+
+	/*
+	 * If the relation is actually a partition, 'parentoid' has been set to
+	 * the OID of the immediate parent.
+	 */
+	if (OidIsValid(parentoid))
+		PG_RETURN_OID(parentoid);
+
+	/* Not a partition, return NULL. */
+	PG_RETURN_NULL();
+}
+
+/*
+ * Returns an integer representing the level a given partition is at in the
+ * partition tree that it's part of.
+ */
+Datum
+pg_partition_level(PG_FUNCTION_ARGS)
+{
+	Oid		reloid = PG_GETARG_OID(0);
+	Oid		rootoid = PG_GETARG_OID(1);
+	List   *ancestors = get_partition_ancestors(reloid);
+	int		level;
+
+	/* If root is specified, find reloid's distance from it. */
+	if (OidIsValid(rootoid))
+	{
+		ListCell *lc;
+
+		if (reloid == rootoid)
+			return 0;
+
+		if (!list_member_oid(ancestors, rootoid))
+			return -1;
+
+		level = 0;
+		foreach(lc, ancestors)
+		{
+			level++;
+			if (lfirst_oid(lc) == rootoid)
+				break;
+		}
+	}
+	else
+		/* Distance from the root of the whole tree. */
+		level = list_length(ancestors);
+
+	list_free(ancestors);
+	PG_RETURN_INT32(level);
+}
+
+/*
+ * Returns OIDs of tables in a partition tree.
+ */
+Datum
+pg_partition_children(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	Oid		reloid = PG_GETARG_OID(0);
+	bool	include_all = PG_GETARG_BOOL(1);
+	List   *partoids;
+	ListCell  **lc;
+
+	/* stuff done only on the first call of the function */
+	if (SRF_IS_FIRSTCALL())
+	{
+		MemoryContext oldcontext;
+
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		if (include_all)
+			partoids = find_all_inheritors(reloid, NoLock, NULL);
+		else
+			partoids = find_inheritance_children(reloid, NoLock);
+		lc = (ListCell **) palloc(sizeof(ListCell *));
+		*lc = list_head(partoids);
+
+		funcctx->user_fctx = (void *) lc;
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	/* stuff done on every call of the function */
+	funcctx = SRF_PERCALL_SETUP();
+	lc = (ListCell **) funcctx->user_fctx;
+
+	while (*lc != NULL)
+	{
+		Oid		partoid = lfirst_oid(*lc);
+
+		*lc = lnext(*lc);
+		SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(partoid));
+	}
+
+	SRF_RETURN_DONE(funcctx);
+}
+
+/*
+ * Returns OIDs of leaf tables in a partition tree.
+ */
+Datum
+pg_partition_leaf_children(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	Oid		reloid = PG_GETARG_OID(0);
+	List   *leafoids;
+	ListCell  **lc;
+
+	/* stuff done only on the first call of the function */
+	if (SRF_IS_FIRSTCALL())
+	{
+		MemoryContext oldcontext;
+
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		leafoids = get_partition_tree_leaf_tables(reloid);
+		lc = (ListCell **) palloc(sizeof(ListCell *));
+		*lc = list_head(leafoids);
+
+		funcctx->user_fctx = (void *) lc;
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	/* stuff done on every call of the function */
+	funcctx = SRF_PERCALL_SETUP();
+	lc = (ListCell **) funcctx->user_fctx;
+
+	while (*lc != NULL)
+	{
+		Oid		partoid = lfirst_oid(*lc);
+
+		*lc = lnext(*lc);
+		SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(partoid));
+	}
+
+	SRF_RETURN_DONE(funcctx);
+}
+
+/*
+ * Returns number of leaf partitions tables in a partition tree
+ */
+static List *
+get_partition_tree_leaf_tables(Oid relid)
+{
+	List   *partitions = find_all_inheritors(relid, NoLock, NULL);
+	ListCell *lc;
+	List   *result = NIL;
+
+	foreach(lc, partitions)
+	{
+		Oid		partoid = lfirst_oid(lc);
+
+		if (get_rel_relkind(partoid) != RELKIND_PARTITIONED_TABLE)
+			result = lappend_oid(result, partoid);
+	}
+
+	list_free(partitions);
+	return result;
+}
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index bba595ad1d..19262c6c4d 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -1821,6 +1821,28 @@ get_rel_relkind(Oid relid)
 }
 
 /*
+ * get_rel_relispartition
+ *
+ *		Returns the value of pg_class.relispartition for a given relation.
+ */
+char
+get_rel_relispartition(Oid relid)
+{
+	HeapTuple	tp;
+	Form_pg_class reltup;
+	bool	result;
+
+	tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
+	if (!HeapTupleIsValid(tp))
+		elog(ERROR, "cache lookup failed for relation %u", relid);
+	reltup = (Form_pg_class) GETSTRUCT(tp);
+	result = reltup->relispartition;
+	ReleaseSysCache(tp);
+
+	return result;
+}
+
+/*
  * get_rel_tablespace
  *
  *		Returns the pg_tablespace OID associated with a given relation.
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index a14651010f..e1d190f81a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10206,4 +10206,52 @@
   proisstrict => 'f', prorettype => 'bool', proargtypes => 'oid int4 int4 any',
   proargmodes => '{i,i,i,v}', prosrc => 'satisfies_hash_partition' },
 
+# function to get the root partition parent
+{ oid => '3423', descr => 'oid of the partition root parent',
+  proname => 'pg_partition_root_parent', prorettype => 'regclass',
+  proargtypes => 'regclass', prosrc => 'pg_partition_root_parent' },
+
+# function to get the partition parent
+{ oid => '3424', descr => 'oid of the partition immediate parent',
+  proname => 'pg_partition_parent', prorettype => 'regclass',
+  proargtypes => 'regclass', prosrc => 'pg_partition_parent' },
+
+# function to get the level of a partition in the partition tree of given root
+{ oid => '3425', descr => 'level of a partition in the partition tree for given root table',
+  proname => 'pg_partition_level', prorettype => 'int4',
+  proargtypes => 'regclass regclass', prosrc => 'pg_partition_level' },
+
+# function to get the level of a partition in the whole partition tree
+{ oid => '3426', descr => 'level of a partition in the partition tree',
+  proname => 'pg_partition_level', prolang => '14', prorettype => 'int4',
+  proargtypes => 'regclass',
+  prosrc => 'select pg_catalog.pg_partition_level($1, \'0\')' },
+
+# function to get OIDs of all tables in a given partition tree
+{ oid => '3427', descr => 'get OIDs of tables in a partition tree',
+  proname => 'pg_partition_children', prorettype => 'regclass',
+  prorows => '100', proretset => 't', proargtypes => 'regclass bool',
+  proallargtypes => '{regclass,bool,regclass}',
+  proargmodes => '{i,i,o}',
+  proargnames => '{relid,include_all,relid}',
+  prosrc => 'pg_partition_children' }
+
+# function to get OIDs of immediate
+{ oid => '3428', descr => 'get OIDs of tables in a partition tree',
+  proname => 'pg_partition_children', prolang => '14', prorettype => 'regclass',
+  prorows => '100', proretset => 't', proargtypes => 'regclass',
+  proallargtypes => '{regclass,regclass}',
+  proargmodes => '{i,o}',
+  proargnames => '{relid,relid}',
+  prosrc => 'select pg_catalog.pg_partition_children($1, \'false\')' }
+
+# function to get OIDs of all tables in a given partition tree
+{ oid => '3429', descr => 'get OIDs of leaf partitions in a partition tree',
+  proname => 'pg_partition_leaf_children', prorettype => 'regclass',
+  prorows => '100', proretset => 't', proargtypes => 'regclass',
+  proallargtypes => '{regclass,regclass}',
+  proargmodes => '{i,o}',
+  proargnames => '{relid,relid}',
+  prosrc => 'pg_partition_leaf_children' }
+
 ]
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index e55ea4035b..d396d17ff1 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -126,6 +126,7 @@ extern char *get_rel_name(Oid relid);
 extern Oid	get_rel_namespace(Oid relid);
 extern Oid	get_rel_type_id(Oid relid);
 extern char get_rel_relkind(Oid relid);
+extern char get_rel_relispartition(Oid relid);
 extern Oid	get_rel_tablespace(Oid relid);
 extern char get_rel_persistence(Oid relid);
 extern Oid	get_transform_fromsql(Oid typid, Oid langid, List *trftypes);
diff --git a/src/test/regress/expected/partition_info.out b/src/test/regress/expected/partition_info.out
new file mode 100644
index 0000000000..e93069913c
--- /dev/null
+++ b/src/test/regress/expected/partition_info.out
@@ -0,0 +1,204 @@
+--
+-- Tests to show partition tree inspection functions
+--
+create table ptif_test (a int, b int) partition by range (a);
+create table ptif_test0 partition of ptif_test for values from (minvalue) to (0) partition by list (b);
+create table ptif_test01 partition of ptif_test0 for values in (1);
+create table ptif_test1 partition of ptif_test for values from (0) to (100) partition by list (b);
+create table ptif_test11 partition of ptif_test1 for values in (1);
+create table ptif_test2 partition of ptif_test for values from (100) to (maxvalue);
+insert into ptif_test select i, 1 from generate_series(-500, 500) i;
+select pg_partition_parent('ptif_test0') as parent;
+  parent   
+-----------
+ ptif_test
+(1 row)
+
+select pg_partition_parent('ptif_test01') as parent;
+   parent   
+------------
+ ptif_test0
+(1 row)
+
+select pg_partition_root_parent('ptif_test01') as root_parent;
+ root_parent 
+-------------
+ ptif_test
+(1 row)
+
+-- pg_partition_level where partition level wrt whole-tree root is returned
+select pg_partition_level('ptif_test01') as level;	-- 2
+ level 
+-------
+     2
+(1 row)
+
+select pg_partition_level('ptif_test0') as level;	-- 1
+ level 
+-------
+     1
+(1 row)
+
+select pg_partition_level('ptif_test') as level;	-- 0
+ level 
+-------
+     0
+(1 row)
+
+select pg_partition_level('ptif_test01', 'ptif_test') as level;	-- 2
+ level 
+-------
+     2
+(1 row)
+
+select pg_partition_level('ptif_test0', 'ptif_test') as level;	-- 1
+ level 
+-------
+     1
+(1 row)
+
+select pg_partition_level('ptif_test', 'ptif_test') as level;	-- 0
+ level 
+-------
+     0
+(1 row)
+
+select pg_partition_level('ptif_test01', 'ptif_test0') as level;	-- 1
+ level 
+-------
+     1
+(1 row)
+
+select pg_partition_level('ptif_test01', 'ptif_test01') as level;	-- 0
+ level 
+-------
+     0
+(1 row)
+
+select pg_partition_level('ptif_test0', 'ptif_test0') as level;		-- 0
+ level 
+-------
+     0
+(1 row)
+
+select pg_partition_level('ptif_test0', 'ptif_test01') as level;	-- -1
+ level 
+-------
+    -1
+(1 row)
+
+-- all tables in the tree
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test', true) p;
+   relname   | level |   parent   | root_parent | size  
+-------------+-------+------------+-------------+-------
+ ptif_test   |     0 |            | ptif_test   |     0
+ ptif_test0  |     1 | ptif_test  | ptif_test   |     0
+ ptif_test1  |     1 | ptif_test  | ptif_test   |     0
+ ptif_test2  |     1 | ptif_test  | ptif_test   | 16384
+ ptif_test01 |     2 | ptif_test0 | ptif_test   | 24576
+ ptif_test11 |     2 | ptif_test1 | ptif_test   |  8192
+(6 rows)
+
+-- only leaf partitions in the tree
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_leaf_children('ptif_test') p;
+   relname   | level |   parent   | root_parent | size  
+-------------+-------+------------+-------------+-------
+ ptif_test2  |     1 | ptif_test  | ptif_test   | 16384
+ ptif_test01 |     2 | ptif_test0 | ptif_test   | 24576
+ ptif_test11 |     2 | ptif_test1 | ptif_test   |  8192
+(3 rows)
+
+-- total relation size grouped by level
+select	pg_partition_level(p) as level,
+		sum(pg_relation_size(p)) as level_size
+from	pg_partition_children('ptif_test', true) p
+group by level order by level;
+ level | level_size 
+-------+------------
+     0 |          0
+     1 |      16384
+     2 |      32768
+(3 rows)
+
+-- total relation size of the whole tree
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_children('ptif_test', true) p;
+ total_size 
+------------
+      49152
+(1 row)
+
+-- total relation size of the leaf partitions; should be same as above
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_leaf_children('ptif_test') p;
+ total_size 
+------------
+      49152
+(1 row)
+
+-- immediate partitions only
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test', false) p;
+  relname   | level |  parent   | root_parent | size  
+------------+-------+-----------+-------------+-------
+ ptif_test0 |     1 | ptif_test | ptif_test   |     0
+ ptif_test1 |     1 | ptif_test | ptif_test   |     0
+ ptif_test2 |     1 | ptif_test | ptif_test   | 16384
+(3 rows)
+
+-- could also be written as
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test') p;
+  relname   | level |  parent   | root_parent | size  
+------------+-------+-----------+-------------+-------
+ ptif_test0 |     1 | ptif_test | ptif_test   |     0
+ ptif_test1 |     1 | ptif_test | ptif_test   |     0
+ ptif_test2 |     1 | ptif_test | ptif_test   | 16384
+(3 rows)
+
+-- immedidate partitions of ptif_test0, which is a non-root partitioned table
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test0') p;
+   relname   | level |   parent   | root_parent | size  
+-------------+-------+------------+-------------+-------
+ ptif_test01 |     2 | ptif_test0 | ptif_test   | 24576
+(1 row)
+
+-- total size of first level partitions
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_children('ptif_test') p;
+ total_size 
+------------
+      16384
+(1 row)
+
+-- number of leaf partitions in the tree
+select count(*) from pg_partition_leaf_children('ptif_test') as num_tables;
+ count 
+-------
+     3
+(1 row)
+
+drop table ptif_test;
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 16f979c8d9..6cb820bbc4 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -116,7 +116,7 @@ test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid c
 # ----------
 # Another group of parallel tests
 # ----------
-test: identity partition_join partition_prune reloptions hash_part indexing partition_aggregate
+test: identity partition_join partition_prune reloptions hash_part indexing partition_aggregate partition_info
 
 # event triggers cannot run concurrently with any test that runs DDL
 test: event_trigger
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 42632be675..7e374c2daa 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -188,6 +188,7 @@ test: reloptions
 test: hash_part
 test: indexing
 test: partition_aggregate
+test: partition_info
 test: event_trigger
 test: fast_default
 test: stats
diff --git a/src/test/regress/sql/partition_info.sql b/src/test/regress/sql/partition_info.sql
new file mode 100644
index 0000000000..5675e8c526
--- /dev/null
+++ b/src/test/regress/sql/partition_info.sql
@@ -0,0 +1,91 @@
+--
+-- Tests to show partition tree inspection functions
+--
+create table ptif_test (a int, b int) partition by range (a);
+create table ptif_test0 partition of ptif_test for values from (minvalue) to (0) partition by list (b);
+create table ptif_test01 partition of ptif_test0 for values in (1);
+create table ptif_test1 partition of ptif_test for values from (0) to (100) partition by list (b);
+create table ptif_test11 partition of ptif_test1 for values in (1);
+create table ptif_test2 partition of ptif_test for values from (100) to (maxvalue);
+insert into ptif_test select i, 1 from generate_series(-500, 500) i;
+
+select pg_partition_parent('ptif_test0') as parent;
+select pg_partition_parent('ptif_test01') as parent;
+select pg_partition_root_parent('ptif_test01') as root_parent;
+
+-- pg_partition_level where partition level wrt whole-tree root is returned
+select pg_partition_level('ptif_test01') as level;	-- 2
+select pg_partition_level('ptif_test0') as level;	-- 1
+select pg_partition_level('ptif_test') as level;	-- 0
+
+select pg_partition_level('ptif_test01', 'ptif_test') as level;	-- 2
+select pg_partition_level('ptif_test0', 'ptif_test') as level;	-- 1
+select pg_partition_level('ptif_test', 'ptif_test') as level;	-- 0
+
+select pg_partition_level('ptif_test01', 'ptif_test0') as level;	-- 1
+select pg_partition_level('ptif_test01', 'ptif_test01') as level;	-- 0
+select pg_partition_level('ptif_test0', 'ptif_test0') as level;		-- 0
+select pg_partition_level('ptif_test0', 'ptif_test01') as level;	-- -1
+
+-- all tables in the tree
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test', true) p;
+
+-- only leaf partitions in the tree
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_leaf_children('ptif_test') p;
+
+-- total relation size grouped by level
+select	pg_partition_level(p) as level,
+		sum(pg_relation_size(p)) as level_size
+from	pg_partition_children('ptif_test', true) p
+group by level order by level;
+
+-- total relation size of the whole tree
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_children('ptif_test', true) p;
+
+-- total relation size of the leaf partitions; should be same as above
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_leaf_children('ptif_test') p;
+
+-- immediate partitions only
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test', false) p;
+
+-- could also be written as
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test') p;
+
+-- immedidate partitions of ptif_test0, which is a non-root partitioned table
+select	p as relname,
+		pg_partition_level(p) as level,
+		pg_partition_parent(p) as parent,
+		pg_partition_root_parent(p) as root_parent,
+		pg_relation_size(p) as size
+from	pg_partition_children('ptif_test0') p;
+
+-- total size of first level partitions
+select	sum(pg_relation_size(p)) as total_size
+from	pg_partition_children('ptif_test') p;
+
+-- number of leaf partitions in the tree
+select count(*) from pg_partition_leaf_children('ptif_test') as num_tables;
+
+drop table ptif_test;
-- 
2.11.0

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