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Fix several DDL issues of generated columns versus inheritance

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Several combinations of generated columns and inheritance in CREATE
TABLE were not handled correctly.  Specifically:

- Disallow a child column specifying a generation expression if the
  parent column is a generated column.  The child column definition
  must be unadorned and the parent column's generation expression will
  be copied.

- Prohibit a child column of a generated parent column specifying
  default values or identity.

- Allow a child column of a not-generated parent column specifying
  itself as a generated column.  This previously did not work, but it
  was possible to arrive at the state via other means (involving ALTER
  TABLE), so it seems sensible to support it.

Add tests for each case.  Also add documentation about the rules
involving generated columns and inheritance.

Discussion:
    https://www.postgresql.org/message-id/flat/15830.1575468847%40sss.pgh.pa.us
    https://www.postgresql.org/message-id/flat/2678bad1-048f-519a-ef24-b12962f41807%40enterprisedb.com
    https://www.postgresql.org/message-id/flat/CAJvUf_u4h0DxkCMCeEKAWCuzGUTnDP-G5iVmSwxLQSXn0_FWNQ%40mail.gmail.com
This commit is contained in:
Peter Eisentraut 2020-05-06 16:25:54 +02:00
parent 501e41dd3c
commit 086ffddf36
4 changed files with 146 additions and 7 deletions
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26
doc/src/sgml/ddl.sgml
View File

@ -324,6 +324,32 @@ CREATE TABLE people (
linkend="sql-createforeigntable"/> for details.
</para>
</listitem>
<listitem>
<para>For inheritance:</para>
<itemizedlist>
<listitem>
<para>
If a parent column is a generated column, a child column must also be
a generated column using the same expression. In the definition of
the child column, leave off the <literal>GENERATED</literal> clause,
as it will be copied from the parent.
</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
same expression.
</para>
</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>
</listitem>
</itemizedlist>
</para>

61
src/backend/commands/tablecmds.c
View File

@ -2618,12 +2618,55 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
def->is_local = true;
/* Merge of NOT NULL constraints = OR 'em together */
def->is_not_null |= newdef->is_not_null;
/*
* Check for conflicts related to generated columns.
*
* If the parent column is generated, the child column must be
* unadorned and will be made a generated column. (We could
* in theory allow the child column definition specifying the
* exact same generation expression, but that's a bit
* complicated to implement and doesn't seem very useful.) We
* also check that the child column doesn't specify a default
* value or identity, which matches the rules for a single
* column in parse_util.c.
*/
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),
errmsg("column \"%s\" inherits from generated column but specifies default",
def->colname)));
if (newdef->identity)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
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;
}
/* If new def has a default, override previous default */
if (newdef->raw_default != NULL)
{
def->raw_default = newdef->raw_default;
def->cooked_default = newdef->cooked_default;
}
}
else
{
@ -2709,11 +2752,19 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
ColumnDef *def = lfirst(entry);
if (def->cooked_default == &bogus_marker)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
errmsg("column \"%s\" inherits conflicting default values",
def->colname),
errhint("To resolve the conflict, specify a default explicitly.")));
{
if (def->generated)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
errmsg("column \"%s\" inherits conflicting generation expressions",
def->colname)));
else
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
errmsg("column \"%s\" inherits conflicting default values",
def->colname),
errhint("To resolve the conflict, specify a default explicitly.")));
}
}
}

44
src/test/regress/expected/generated.out
View File

@ -219,12 +219,54 @@ SELECT * FROM gtest1;
4 | 8
(2 rows)
-- test inheritance mismatch
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);
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)
-- 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.
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
-- test multiple inheritance mismatches
CREATE TABLE gtesty (x int, b int);
CREATE TABLE gtest1_2 () 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
NOTICE: merging multiple inherited definitions of column "b"
ERROR: column "b" inherits conflicting generation expressions
DROP TABLE gtesty;
CREATE TABLE gtesty (x int, b int DEFAULT 55);
CREATE TABLE gtest1_2 () INHERITS (gtest0, gtesty); -- error
NOTICE: merging multiple inherited definitions of column "b"
ERROR: inherited column "b" has a generation conflict
DROP TABLE gtesty;
-- test stored update
CREATE TABLE gtest3 (a int, b int GENERATED ALWAYS AS (a * 3) STORED);
INSERT INTO gtest3 (a) VALUES (1), (2), (3), (NULL);

22
src/test/regress/sql/generated.sql
View File

@ -89,11 +89,31 @@ INSERT INTO gtest1_1 VALUES (4);
SELECT * FROM gtest1_1;
SELECT * FROM gtest1;
-- test inheritance mismatch
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);
\d gtest_normal_child
INSERT INTO gtest_normal (a) VALUES (1);
INSERT INTO gtest_normal_child (a) VALUES (2);
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
-- test multiple inheritance mismatches
CREATE TABLE gtesty (x int, b int);
CREATE TABLE gtest1_2 () 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
DROP TABLE gtesty;
CREATE TABLE gtesty (x int, b int DEFAULT 55);
CREATE TABLE gtest1_2 () INHERITS (gtest0, gtesty); -- error
DROP TABLE gtesty;
-- test stored update
CREATE TABLE gtest3 (a int, b int GENERATED ALWAYS AS (a * 3) STORED);
INSERT INTO gtest3 (a) VALUES (1), (2), (3), (NULL);