Improve handling of inherited GENERATED expressions.

In both partitioning and traditional inheritance, require child
columns to be GENERATED if and only if their parent(s) are.
Formerly we allowed the case of an inherited column being
GENERATED when its parent isn't, but that results in inconsistent
behavior: the column can be directly updated through an UPDATE
on the parent table, leading to it containing a user-supplied
value that might not match the generation expression.  This also
fixes an oversight that we enforced partition-key-columns-can't-
be-GENERATED against parent tables, but not against child tables
that were dynamically attached to them.

Also, remove the restriction that the child's generation expression
be equivalent to the parent's.  In the wake of commit 3f7836ff6,
there doesn't seem to be any reason that we need that restriction,
since generation expressions are always computed per-table anyway.
By removing this, we can also allow a child to merge multiple
inheritance parents with inconsistent generation expressions, by
overriding them with its own expression, much as we've long allowed
for DEFAULT expressions.

Since we're rejecting a case that we used to accept, this doesn't
seem like a back-patchable change.  Given the lack of field
complaints about the inconsistent behavior, it's likely that no
one is doing this anyway, but we won't change it in minor releases.

Amit Langote and Tom Lane

Discussion: https://postgr.es/m/2793383.1672944799@sss.pgh.pa.us

doc/src/sgml/ddl.sgml

@@ -325,27 +325,54 @@ CREATE TABLE people (
      </para>
     </listitem>
     <listitem>
-     <para>For inheritance:</para>
+     <para>For inheritance and partitioning:</para>
      <itemizedlist>
       <listitem>
        <para>
-        If a parent column is a generated column, a child column must also be
+        If a parent column is a generated column, its child column must also
-        a generated column using the same expression.  In the definition of
+        be a generated column; however, the child column can have a
-        the child column, leave off the <literal>GENERATED</literal> clause,
+        different generation expression.  The generation expression that is
-        as it will be copied from the parent.
+        actually applied during insert or update of a row is the one
+        associated with the table that the row is physically in.
+        (This is unlike the behavior for column defaults: for those, the
+        default value associated with the table named in the query applies.)
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        If a parent column is not a generated column, its child column must
+        not be generated either.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        For inherited tables, if you write a child column definition without
+        any <literal>GENERATED</literal> clause in <command>CREATE TABLE
+        ... INHERITS</command>, then its <literal>GENERATED</literal> clause
+        will automatically be copied from the parent.  <command>ALTER TABLE
+        ... INHERIT</command> will insist that parent and child columns
+        already match as to generation status, but it will not require their
+        generation expressions to match.
+       </para>
+      </listitem>
+      <listitem>
+       <para>
+        Similarly for partitioned tables, if you write a child column
+        definition without any <literal>GENERATED</literal> clause
+        in <command>CREATE TABLE ... PARTITION OF</command>, then
+        its <literal>GENERATED</literal> clause will automatically be copied
+        from the parent.  <command>ALTER TABLE ... ADD PARTITION</command>
+        will insist that parent and child columns already match as to
+        generation status, but it will not require their generation
+        expressions to match.
        </para>
       </listitem>
       <listitem>
        <para>
         In case of multiple inheritance, if one parent column is a generated
-        column, then all parent columns must be generated columns and with the
+        column, then all parent columns must be generated columns.  If they
-        same expression.
+        do not all have the same generation expression, then the desired
-       </para>
+        expression for the child must be specified explicitly.
-      </listitem>
-      <listitem>
-       <para>
-        If a parent column is not a generated column, a child column may be
-        defined to be a generated column or not.
        </para>
       </listitem>
      </itemizedlist>

src/backend/commands/tablecmds.c

@@ -2320,8 +2320,12 @@ storage_name(char c)
  *		(3) If conflicting defaults are inherited from different parents
  *			(and not overridden by the child), an error is raised.
  *		(4) Otherwise the inherited default is used.
- *		Rule (3) is new in Postgres 7.1; in earlier releases you got a
+ *
- *		rather arbitrary choice of which parent default to use.
+ *		Note that the default-value infrastructure is used for generated
+ *		columns' expressions too, so most of the preceding paragraph applies
+ *		to generation expressions too.  We insist that a child column be
+ *		generated if and only if its parent(s) are, but it need not have
+ *		the same generation expression.
  *----------
  */
 static List *
@@ -2659,7 +2663,7 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 			}
 
 			/*
-			 * Locate default if any
+			 * Locate default/generation expression if any
 			 */
 			if (attribute->atthasdef)
 			{
@@ -2923,23 +2927,20 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 				/*
 				 * Check for conflicts related to generated columns.
 				 *
-				 * If the parent column is generated, the child column must be
+				 * If the parent column is generated, the child column will be
-				 * unadorned and will be made a generated column.  (We could
+				 * made a generated column if it isn't already.  If it is a
-				 * in theory allow the child column definition specifying the
+				 * generated column, we'll take its generation expression in
-				 * exact same generation expression, but that's a bit
+				 * preference to the parent's.  We must check that the child
-				 * complicated to implement and doesn't seem very useful.)  We
+				 * column doesn't specify a default value or identity, which
-				 * also check that the child column doesn't specify a default
+				 * matches the rules for a single column in parse_util.c.
-				 * value or identity, which matches the rules for a single
+				 *
-				 * column in parse_util.c.
+				 * Conversely, if the parent column is not generated, the
+				 * child column can't be either.  (We used to allow that, but
+				 * it results in being able to override the generation
+				 * expression via UPDATEs through the parent.)
 				 */
 				if (def->generated)
 				{
-					if (newdef->generated)
-						ereport(ERROR,
-								(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
-								 errmsg("child column \"%s\" specifies generation expression",
-										def->colname),
-								 errhint("Omit the generation expression in the definition of the child table column to inherit the generation expression from the parent table.")));
 					if (newdef->raw_default && !newdef->generated)
 						ereport(ERROR,
 								(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
@@ -2951,15 +2952,14 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 								 errmsg("column \"%s\" inherits from generated column but specifies identity",
 										def->colname)));
 				}
-
-				/*
-				 * If the parent column is not generated, then take whatever
-				 * the child column definition says.
-				 */
 				else
 				{
 					if (newdef->generated)
-						def->generated = newdef->generated;
+						ereport(ERROR,
+								(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
+								 errmsg("child column \"%s\" specifies generation expression",
+										def->colname),
+								 errhint("A child table column cannot be generated unless its parent column is.")));
 				}
 
 				/* If new def has a default, override previous default */
@@ -2994,8 +2994,8 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 	/*
 	 * Now that we have the column definition list for a partition, we can
 	 * check whether the columns referenced in the column constraint specs
-	 * actually exist.  Also, we merge NOT NULL and defaults into each
+	 * actually exist.  Also, we merge parent's NOT NULL constraints and
-	 * corresponding column definition.
+	 * defaults into each corresponding column definition.
 	 */
 	if (is_partition)
 	{
@@ -3014,6 +3014,19 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 					found = true;
 					coldef->is_not_null |= restdef->is_not_null;
 
+					/*
+					 * As above, reject generated columns in partitions that
+					 * are not generated in the parent.
+					 */
+					if (restdef->generated && !coldef->generated)
+						ereport(ERROR,
+								(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
+								 errmsg("child column \"%s\" specifies generation expression",
+										restdef->colname),
+								 errhint("A child table column cannot be generated unless its parent column is.")));
+					/* Other way around should have been dealt with above */
+					Assert(!(coldef->generated && !restdef->generated));
+
 					/*
 					 * Override the parent's default value for this column
 					 * (coldef->cooked_default) with the partition's local
@@ -3058,7 +3071,8 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
 					ereport(ERROR,
 							(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
 							 errmsg("column \"%s\" inherits conflicting generation expressions",
-									def->colname)));
+									def->colname),
+							 errhint("To resolve the conflict, specify a generation expression explicitly.")));
 				else
 					ereport(ERROR,
 							(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
@@ -15038,64 +15052,18 @@ MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel)
 								attributeName)));
 
 			/*
-			 * If parent column is generated, child column must be, too.
+			 * Child column must be generated if and only if parent column is.
 			 */
 			if (attribute->attgenerated && !childatt->attgenerated)
 				ereport(ERROR,
 						(errcode(ERRCODE_DATATYPE_MISMATCH),
 						 errmsg("column \"%s\" in child table must be a generated column",
 								attributeName)));
-
+			if (childatt->attgenerated && !attribute->attgenerated)
-			/*
+				ereport(ERROR,
-			 * Check that both generation expressions match.
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
-			 *
+						 errmsg("column \"%s\" in child table must not be a generated column",
-			 * The test we apply is to see whether they reverse-compile to the
+								attributeName)));
-			 * same source string.  This insulates us from issues like whether
-			 * attributes have the same physical column numbers in parent and
-			 * child relations.  (See also constraints_equivalent().)
-			 */
-			if (attribute->attgenerated && childatt->attgenerated)
-			{
-				TupleConstr *child_constr = child_rel->rd_att->constr;
-				TupleConstr *parent_constr = parent_rel->rd_att->constr;
-				char	   *child_expr = NULL;
-				char	   *parent_expr = NULL;
-
-				Assert(child_constr != NULL);
-				Assert(parent_constr != NULL);
-
-				for (int i = 0; i < child_constr->num_defval; i++)
-				{
-					if (child_constr->defval[i].adnum == childatt->attnum)
-					{
-						child_expr =
-							TextDatumGetCString(DirectFunctionCall2(pg_get_expr,
-																	CStringGetTextDatum(child_constr->defval[i].adbin),
-																	ObjectIdGetDatum(child_rel->rd_id)));
-						break;
-					}
-				}
-				Assert(child_expr != NULL);
-
-				for (int i = 0; i < parent_constr->num_defval; i++)
-				{
-					if (parent_constr->defval[i].adnum == attribute->attnum)
-					{
-						parent_expr =
-							TextDatumGetCString(DirectFunctionCall2(pg_get_expr,
-																	CStringGetTextDatum(parent_constr->defval[i].adbin),
-																	ObjectIdGetDatum(parent_rel->rd_id)));
-						break;
-					}
-				}
-				Assert(parent_expr != NULL);
-
-				if (strcmp(child_expr, parent_expr) != 0)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATATYPE_MISMATCH),
-							 errmsg("column \"%s\" in child table has a conflicting generation expression",
-									attributeName)));
-			}
 
 			/*
 			 * OK, bump the child column's inheritance count.  (If we fail

src/backend/parser/parse_utilcmd.c

@@ -740,11 +740,6 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							 errmsg("generated columns are not supported on typed tables")));
-				if (cxt->partbound)
-					ereport(ERROR,
-							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("generated columns are not supported on partitions")));
-
 				if (saw_generated)
 					ereport(ERROR,
 							(errcode(ERRCODE_SYNTAX_ERROR),

src/bin/pg_dump/common.c

@@ -452,14 +452,15 @@ flagInhIndexes(Archive *fout, TableInfo tblinfo[], int numTables)
  *   that we'll correctly emit the necessary DEFAULT NULL clause; otherwise
  *   the backend will apply an inherited default to the column.
  *
- * - Detect child columns that have a generation expression when their parents
+ * - Detect child columns that have a generation expression and all their
- *   also have one.  Generation expressions are always inherited, so there is
+ *   parents also have the same generation expression, and if so suppress the
- *   no need to set them again in child tables, and there is no syntax for it
+ *   child's expression.  The child will inherit the generation expression
- *   either.  Exceptions: If it's a partition or we are in binary upgrade
+ *   automatically, so there's no need to dump it.  This improves the dump's
- *   mode, we dump them because in those cases inherited tables are recreated
+ *   compatibility with pre-v16 servers, which didn't allow the child's
- *   standalone first and then reattached to the parent.  (See also the logic
+ *   expression to be given explicitly.  Exceptions: If it's a partition or
- *   in dumpTableSchema().)  In that situation, the generation expressions
+ *   we are in binary upgrade mode, we dump such expressions anyway because
- *   must match the parent, enforced by ALTER TABLE.
+ *   in those cases inherited tables are recreated standalone first and then
+ *   reattached to the parent.  (See also the logic in dumpTableSchema().)
  *
  * modifies tblinfo
  */
@@ -497,7 +498,8 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 		{
 			bool		foundNotNull;	/* Attr was NOT NULL in a parent */
 			bool		foundDefault;	/* Found a default in a parent */
-			bool		foundGenerated; /* Found a generated in a parent */
+			bool		foundSameGenerated; /* Found matching GENERATED */
+			bool		foundDiffGenerated; /* Found non-matching GENERATED */
 
 			/* no point in examining dropped columns */
 			if (tbinfo->attisdropped[j])
@@ -505,7 +507,8 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 
 			foundNotNull = false;
 			foundDefault = false;
-			foundGenerated = false;
+			foundSameGenerated = false;
+			foundDiffGenerated = false;
 			for (k = 0; k < numParents; k++)
 			{
 				TableInfo  *parent = parents[k];
@@ -517,8 +520,19 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 				if (inhAttrInd >= 0)
 				{
 					foundNotNull |= parent->notnull[inhAttrInd];
-					foundDefault |= (parent->attrdefs[inhAttrInd] != NULL && !parent->attgenerated[inhAttrInd]);
+					foundDefault |= (parent->attrdefs[inhAttrInd] != NULL &&
-					foundGenerated |= parent->attgenerated[inhAttrInd];
+									 !parent->attgenerated[inhAttrInd]);
+					if (parent->attgenerated[inhAttrInd])
+					{
+						/* these pointer nullness checks are just paranoia */
+						if (parent->attrdefs[inhAttrInd] != NULL &&
+							tbinfo->attrdefs[j] != NULL &&
+							strcmp(parent->attrdefs[inhAttrInd]->adef_expr,
+								   tbinfo->attrdefs[j]->adef_expr) == 0)
+							foundSameGenerated = true;
+						else
+							foundDiffGenerated = true;
+					}
 				}
 			}
 
@@ -561,8 +575,9 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 				tbinfo->attrdefs[j] = attrDef;
 			}
 
-			/* Remove generation expression from child */
+			/* Remove generation expression from child if possible */
-			if (foundGenerated && !tbinfo->ispartition && !dopt->binary_upgrade)
+			if (foundSameGenerated && !foundDiffGenerated &&
+				!tbinfo->ispartition && !dopt->binary_upgrade)
 				tbinfo->attrdefs[j] = NULL;
 		}
 	}

src/bin/pg_dump/pg_dump.c

@@ -8529,17 +8529,11 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 			{
 				/*
 				 * Column generation expressions cannot be dumped separately,
-				 * because there is no syntax for it.  The !shouldPrintColumn
+				 * because there is no syntax for it.  By setting separate to
-				 * case below will be tempted to set them to separate if they
-				 * are attached to an inherited column without a local
-				 * definition, but that would be wrong and unnecessary,
-				 * because generation expressions are always inherited, so
-				 * there is no need to set them again in child tables, and
-				 * there is no syntax for it either.  By setting separate to
 				 * false here we prevent the "default" from being processed as
 				 * its own dumpable object, and flagInhAttrs() will remove it
-				 * from the table when it detects that it belongs to an
+				 * from the table if possible (that is, if it can be inherited
-				 * inherited column.
+				 * from a parent).
 				 */
 				attrdefs[j].separate = false;
 			}

src/test/regress/expected/generated.out

@@ -268,75 +268,72 @@ SELECT * FROM gtest1;
  4 | 8
 (2 rows)
 
+-- can't have generated column that is a child of normal column
 CREATE TABLE gtest_normal (a int, b int);
-CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED) INHERITS (gtest_normal);
+CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED) INHERITS (gtest_normal);  -- error
 NOTICE:  merging column "a" with inherited definition
 NOTICE:  merging column "b" with inherited definition
-\d gtest_normal_child
-                      Table "public.gtest_normal_child"
- Column |  Type   | Collation | Nullable |              Default               
---------+---------+-----------+----------+------------------------------------
- a      | integer |           |          | 
- b      | integer |           |          | generated always as (a * 2) stored
-Inherits: gtest_normal
-
-INSERT INTO gtest_normal (a) VALUES (1);
-INSERT INTO gtest_normal_child (a) VALUES (2);
-SELECT * FROM gtest_normal;
- a | b 
----+---
- 1 |  
- 2 | 4
-(2 rows)
-
-CREATE TABLE gtest_normal_child2 (a int, b int GENERATED ALWAYS AS (a * 3) STORED);
-ALTER TABLE gtest_normal_child2 INHERIT gtest_normal;
-INSERT INTO gtest_normal_child2 (a) VALUES (3);
-SELECT * FROM gtest_normal;
- a | b 
----+---
- 1 |  
- 2 | 4
- 3 | 9
-(3 rows)
-
--- test inheritance mismatches between parent and child
-CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS (a * 22) STORED) INHERITS (gtest1);  -- error
-NOTICE:  merging column "b" with inherited definition
 ERROR:  child column "b" specifies generation expression
-HINT:  Omit the generation expression in the definition of the child table column to inherit the generation expression from the parent table.
+HINT:  A child table column cannot be generated unless its parent column is.
+CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED);
+ALTER TABLE gtest_normal_child INHERIT gtest_normal;  -- error
+ERROR:  column "b" in child table must not be a generated column
+DROP TABLE gtest_normal, gtest_normal_child;
+-- test inheritance mismatches between parent and child
 CREATE TABLE gtestx (x int, b int DEFAULT 10) INHERITS (gtest1);  -- error
 NOTICE:  merging column "b" with inherited definition
 ERROR:  column "b" inherits from generated column but specifies default
 CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS IDENTITY) INHERITS (gtest1);  -- error
 NOTICE:  merging column "b" with inherited definition
 ERROR:  column "b" inherits from generated column but specifies identity
+CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS (a * 22) STORED) INHERITS (gtest1);  -- ok, overrides parent
+NOTICE:  merging column "b" with inherited definition
+\d+ gtestx
+                                                Table "public.gtestx"
+ Column |  Type   | Collation | Nullable |               Default               | Storage | Stats target | Description 
+--------+---------+-----------+----------+-------------------------------------+---------+--------------+-------------
+ a      | integer |           | not null |                                     | plain   |              | 
+ b      | integer |           |          | generated always as (a * 22) stored | plain   |              | 
+ x      | integer |           |          |                                     | plain   |              | 
+Inherits: gtest1
+
 CREATE TABLE gtestxx_1 (a int NOT NULL, b int);
 ALTER TABLE gtestxx_1 INHERIT gtest1;  -- error
 ERROR:  column "b" in child table must be a generated column
-CREATE TABLE gtestxx_2 (a int NOT NULL, b int GENERATED ALWAYS AS (a * 22) STORED);
-ALTER TABLE gtestxx_2 INHERIT gtest1;  -- error
-ERROR:  column "b" in child table has a conflicting generation expression
 CREATE TABLE gtestxx_3 (a int NOT NULL, b int GENERATED ALWAYS AS (a * 2) STORED);
 ALTER TABLE gtestxx_3 INHERIT gtest1;  -- ok
 CREATE TABLE gtestxx_4 (b int GENERATED ALWAYS AS (a * 2) STORED, a int NOT NULL);
 ALTER TABLE gtestxx_4 INHERIT gtest1;  -- ok
 -- test multiple inheritance mismatches
+CREATE TABLE gtesty (x int, b int DEFAULT 55);
+CREATE TABLE gtest1_y () INHERITS (gtest0, gtesty);  -- error
+NOTICE:  merging multiple inherited definitions of column "b"
+ERROR:  inherited column "b" has a generation conflict
+DROP TABLE gtesty;
 CREATE TABLE gtesty (x int, b int);
-CREATE TABLE gtest1_2 () INHERITS (gtest1, gtesty);  -- error
+CREATE TABLE gtest1_y () INHERITS (gtest1, gtesty);  -- error
 NOTICE:  merging multiple inherited definitions of column "b"
 ERROR:  inherited column "b" has a generation conflict
 DROP TABLE gtesty;
 CREATE TABLE gtesty (x int, b int GENERATED ALWAYS AS (x * 22) STORED);
-CREATE TABLE gtest1_2 () INHERITS (gtest1, gtesty);  -- error
+CREATE TABLE gtest1_y () INHERITS (gtest1, gtesty);  -- error
 NOTICE:  merging multiple inherited definitions of column "b"
 ERROR:  column "b" inherits conflicting generation expressions
-DROP TABLE gtesty;
+HINT:  To resolve the conflict, specify a generation expression explicitly.
-CREATE TABLE gtesty (x int, b int DEFAULT 55);
+CREATE TABLE gtest1_y (b int GENERATED ALWAYS AS (x + 1) STORED) INHERITS (gtest1, gtesty);  -- ok
-CREATE TABLE gtest1_2 () INHERITS (gtest0, gtesty);  -- error
 NOTICE:  merging multiple inherited definitions of column "b"
-ERROR:  inherited column "b" has a generation conflict
+NOTICE:  moving and merging column "b" with inherited definition
-DROP TABLE gtesty;
+DETAIL:  User-specified column moved to the position of the inherited column.
+\d gtest1_y
+                           Table "public.gtest1_y"
+ Column |  Type   | Collation | Nullable |              Default               
+--------+---------+-----------+----------+------------------------------------
+ a      | integer |           | not null | 
+ b      | integer |           |          | generated always as (x + 1) stored
+ x      | integer |           |          | 
+Inherits: gtest1,
+          gtesty
+
 -- test correct handling of GENERATED column that's only in child
 CREATE TABLE gtestp (f1 int);
 CREATE TABLE gtestc (f2 int GENERATED ALWAYS AS (f1+1) STORED) INHERITS(gtestp);
@@ -696,16 +693,56 @@ CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
 CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) STORED);
 ERROR:  generated columns are not supported on typed tables
 DROP TYPE gtest_type CASCADE;
--- table partitions (currently not supported)
+-- partitioning cases
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 text, f3 bigint) PARTITION BY RANGE (f1);
+CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint) PARTITION BY RANGE (f1);
 CREATE TABLE gtest_child PARTITION OF gtest_parent (
     f3 WITH OPTIONS GENERATED ALWAYS AS (f2 * 2) STORED
 ) FOR VALUES FROM ('2016-07-01') TO ('2016-08-01'); -- error
-ERROR:  generated columns are not supported on partitions
+ERROR:  child column "f3" specifies generation expression
-DROP TABLE gtest_parent;
+HINT:  A child table column cannot be generated unless its parent column is.
--- partitioned table
+CREATE TABLE gtest_child (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child FOR VALUES FROM ('2016-07-01') TO ('2016-08-01'); -- error
+ERROR:  column "f3" in child table must not be a generated column
+DROP TABLE gtest_parent, gtest_child;
 CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f1);
-CREATE TABLE gtest_child PARTITION OF gtest_parent FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
+CREATE TABLE gtest_child PARTITION OF gtest_parent
+  FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');  -- inherits gen expr
+CREATE TABLE gtest_child2 PARTITION OF gtest_parent (
+    f3 WITH OPTIONS GENERATED ALWAYS AS (f2 * 22) STORED  -- overrides gen expr
+) FOR VALUES FROM ('2016-08-01') TO ('2016-09-01');
+CREATE TABLE gtest_child3 (f1 date NOT NULL, f2 bigint, f3 bigint);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child3 FOR VALUES FROM ('2016-09-01') TO ('2016-10-01'); -- error
+ERROR:  column "f3" in child table must be a generated column
+DROP TABLE gtest_child3;
+CREATE TABLE gtest_child3 (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 33) STORED);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child3 FOR VALUES FROM ('2016-09-01') TO ('2016-10-01');
+\d gtest_child
+                          Table "public.gtest_child"
+ Column |  Type  | Collation | Nullable |               Default               
+--------+--------+-----------+----------+-------------------------------------
+ f1     | date   |           | not null | 
+ f2     | bigint |           |          | 
+ f3     | bigint |           |          | generated always as (f2 * 2) stored
+Partition of: gtest_parent FOR VALUES FROM ('07-01-2016') TO ('08-01-2016')
+
+\d gtest_child2
+                          Table "public.gtest_child2"
+ Column |  Type  | Collation | Nullable |               Default                
+--------+--------+-----------+----------+--------------------------------------
+ f1     | date   |           | not null | 
+ f2     | bigint |           |          | 
+ f3     | bigint |           |          | generated always as (f2 * 22) stored
+Partition of: gtest_parent FOR VALUES FROM ('08-01-2016') TO ('09-01-2016')
+
+\d gtest_child3
+                          Table "public.gtest_child3"
+ Column |  Type  | Collation | Nullable |               Default                
+--------+--------+-----------+----------+--------------------------------------
+ f1     | date   |           | not null | 
+ f2     | bigint |           |          | 
+ f3     | bigint |           |          | generated always as (f2 * 33) stored
+Partition of: gtest_parent FOR VALUES FROM ('09-01-2016') TO ('10-01-2016')
+
 INSERT INTO gtest_parent (f1, f2) VALUES ('2016-07-15', 1);
 SELECT * FROM gtest_parent;
      f1     | f2 | f3 
@@ -719,14 +756,14 @@ SELECT * FROM gtest_child;
  07-15-2016 |  1 |  2
 (1 row)
 
-DROP TABLE gtest_parent;
+-- we leave these tables around for purposes of testing dump/reload/upgrade
 -- generated columns in partition key (not allowed)
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f3);
+CREATE TABLE gtest_part_key (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f3);
 ERROR:  cannot use generated column in partition key
 LINE 1: ...ENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f3);
                                                                    ^
 DETAIL:  Column "f3" is a generated column.
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE ((f3 * 3));
+CREATE TABLE gtest_part_key (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE ((f3 * 3));
 ERROR:  cannot use generated column in partition key
 LINE 1: ...ED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE ((f3 * 3));
                                                              ^

src/test/regress/sql/generated.sql

@@ -110,44 +110,39 @@ INSERT INTO gtest1_1 VALUES (4);
 SELECT * FROM gtest1_1;
 SELECT * FROM gtest1;
 
+-- can't have generated column that is a child of normal column
 CREATE TABLE gtest_normal (a int, b int);
-CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED) INHERITS (gtest_normal);
+CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED) INHERITS (gtest_normal);  -- error
-\d gtest_normal_child
+CREATE TABLE gtest_normal_child (a int, b int GENERATED ALWAYS AS (a * 2) STORED);
-INSERT INTO gtest_normal (a) VALUES (1);
+ALTER TABLE gtest_normal_child INHERIT gtest_normal;  -- error
-INSERT INTO gtest_normal_child (a) VALUES (2);
+DROP TABLE gtest_normal, gtest_normal_child;
-SELECT * FROM gtest_normal;
-
-CREATE TABLE gtest_normal_child2 (a int, b int GENERATED ALWAYS AS (a * 3) STORED);
-ALTER TABLE gtest_normal_child2 INHERIT gtest_normal;
-INSERT INTO gtest_normal_child2 (a) VALUES (3);
-SELECT * FROM gtest_normal;
 
 -- test inheritance mismatches between parent and child
-CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS (a * 22) STORED) INHERITS (gtest1);  -- error
 CREATE TABLE gtestx (x int, b int DEFAULT 10) INHERITS (gtest1);  -- error
 CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS IDENTITY) INHERITS (gtest1);  -- error
+CREATE TABLE gtestx (x int, b int GENERATED ALWAYS AS (a * 22) STORED) INHERITS (gtest1);  -- ok, overrides parent
+\d+ gtestx
 
 CREATE TABLE gtestxx_1 (a int NOT NULL, b int);
 ALTER TABLE gtestxx_1 INHERIT gtest1;  -- error
-CREATE TABLE gtestxx_2 (a int NOT NULL, b int GENERATED ALWAYS AS (a * 22) STORED);
-ALTER TABLE gtestxx_2 INHERIT gtest1;  -- error
 CREATE TABLE gtestxx_3 (a int NOT NULL, b int GENERATED ALWAYS AS (a * 2) STORED);
 ALTER TABLE gtestxx_3 INHERIT gtest1;  -- ok
 CREATE TABLE gtestxx_4 (b int GENERATED ALWAYS AS (a * 2) STORED, a int NOT NULL);
 ALTER TABLE gtestxx_4 INHERIT gtest1;  -- ok
 
 -- test multiple inheritance mismatches
+CREATE TABLE gtesty (x int, b int DEFAULT 55);
+CREATE TABLE gtest1_y () INHERITS (gtest0, gtesty);  -- error
+DROP TABLE gtesty;
+
 CREATE TABLE gtesty (x int, b int);
-CREATE TABLE gtest1_2 () INHERITS (gtest1, gtesty);  -- error
+CREATE TABLE gtest1_y () INHERITS (gtest1, gtesty);  -- error
 DROP TABLE gtesty;
 
 CREATE TABLE gtesty (x int, b int GENERATED ALWAYS AS (x * 22) STORED);
-CREATE TABLE gtest1_2 () INHERITS (gtest1, gtesty);  -- error
+CREATE TABLE gtest1_y () INHERITS (gtest1, gtesty);  -- error
-DROP TABLE gtesty;
+CREATE TABLE gtest1_y (b int GENERATED ALWAYS AS (x + 1) STORED) INHERITS (gtest1, gtesty);  -- ok
-
+\d gtest1_y
-CREATE TABLE gtesty (x int, b int DEFAULT 55);
-CREATE TABLE gtest1_2 () INHERITS (gtest0, gtesty);  -- error
-DROP TABLE gtesty;
 
 -- test correct handling of GENERATED column that's only in child
 CREATE TABLE gtestp (f1 int);
@@ -365,24 +360,37 @@ CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
 CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) STORED);
 DROP TYPE gtest_type CASCADE;
 
--- table partitions (currently not supported)
+-- partitioning cases
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 text, f3 bigint) PARTITION BY RANGE (f1);
+CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint) PARTITION BY RANGE (f1);
 CREATE TABLE gtest_child PARTITION OF gtest_parent (
     f3 WITH OPTIONS GENERATED ALWAYS AS (f2 * 2) STORED
 ) FOR VALUES FROM ('2016-07-01') TO ('2016-08-01'); -- error
-DROP TABLE gtest_parent;
+CREATE TABLE gtest_child (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child FOR VALUES FROM ('2016-07-01') TO ('2016-08-01'); -- error
+DROP TABLE gtest_parent, gtest_child;
 
--- partitioned table
 CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f1);
-CREATE TABLE gtest_child PARTITION OF gtest_parent FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');
+CREATE TABLE gtest_child PARTITION OF gtest_parent
+  FOR VALUES FROM ('2016-07-01') TO ('2016-08-01');  -- inherits gen expr
+CREATE TABLE gtest_child2 PARTITION OF gtest_parent (
+    f3 WITH OPTIONS GENERATED ALWAYS AS (f2 * 22) STORED  -- overrides gen expr
+) FOR VALUES FROM ('2016-08-01') TO ('2016-09-01');
+CREATE TABLE gtest_child3 (f1 date NOT NULL, f2 bigint, f3 bigint);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child3 FOR VALUES FROM ('2016-09-01') TO ('2016-10-01'); -- error
+DROP TABLE gtest_child3;
+CREATE TABLE gtest_child3 (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 33) STORED);
+ALTER TABLE gtest_parent ATTACH PARTITION gtest_child3 FOR VALUES FROM ('2016-09-01') TO ('2016-10-01');
+\d gtest_child
+\d gtest_child2
+\d gtest_child3
 INSERT INTO gtest_parent (f1, f2) VALUES ('2016-07-15', 1);
 SELECT * FROM gtest_parent;
 SELECT * FROM gtest_child;
-DROP TABLE gtest_parent;
+-- we leave these tables around for purposes of testing dump/reload/upgrade
 
 -- generated columns in partition key (not allowed)
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f3);
+CREATE TABLE gtest_part_key (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE (f3);
-CREATE TABLE gtest_parent (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE ((f3 * 3));
+CREATE TABLE gtest_part_key (f1 date NOT NULL, f2 bigint, f3 bigint GENERATED ALWAYS AS (f2 * 2) STORED) PARTITION BY RANGE ((f3 * 3));
 
 -- ALTER TABLE ... ADD COLUMN
 CREATE TABLE gtest25 (a int PRIMARY KEY);