From 2c82a0f77ff676634e27782b147fce9c0089fb78 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Wed, 6 May 2020 16:25:54 +0200 Subject: [PATCH] Fix several DDL issues of generated columns versus inheritance 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 --- doc/src/sgml/ddl.sgml | 26 +++++++++++ src/backend/commands/tablecmds.c | 61 +++++++++++++++++++++++-- src/test/regress/expected/generated.out | 44 +++++++++++++++++- src/test/regress/sql/generated.sql | 22 ++++++++- 4 files changed, 146 insertions(+), 7 deletions(-) diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index a20e5fb366..bf9f0181ea 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -324,6 +324,32 @@ Generated Columns linkend="sql-createforeigntable"/> for details. + + For inheritance: + + + + 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 GENERATED clause, + as it will be copied from the parent. + + + + + 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. + + + + + If a parent column is not a generated column, a child column may be + defined to be a generated column or not. + + + + diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 1a6ccff8f1..673166bca5 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -2577,12 +2577,55 @@ 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("Leave off 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 { @@ -2668,11 +2711,19 @@ 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."))); + } } } diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out index f87c86a8ce..0436773628 100644 --- a/src/test/regress/expected/generated.out +++ b/src/test/regress/expected/generated.out @@ -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: Leave off 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); diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql index bdcedbb991..f089f9a74d 100644 --- a/src/test/regress/sql/generated.sql +++ b/src/test/regress/sql/generated.sql @@ -89,11 +89,31 @@ CREATE TABLE gtest1_1 () INHERITS (gtest1); 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); base-commit: 987717d7c7007055ff7fc2ecf3d40e9bdb00e071 -- 2.26.2