From 61feb8670824c8dfb66094f2a87df2395be0665c Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 21 May 2021 15:12:08 -0400 Subject: [PATCH] Disallow whole-row variables in GENERATED expressions. This was previously allowed, but I think that was just an oversight. It's a clear violation of the rule that a generated column cannot depend on itself or other generated columns. Moreover, because the code was relying on the assumption that no such cross-references exist, it was pretty easy to crash ALTER TABLE and perhaps other places. Even if you managed not to crash, you got quite unstable, implementation-dependent results. Per report from Vitaly Ustinov. Back-patch to v12 where GENERATED came in. Discussion: https://postgr.es/m/CAM_DEiWR2DPT6U4xb-Ehigozzd3n3G37ZB1+867zbsEVtYoJww@mail.gmail.com --- src/backend/catalog/heap.c | 15 +++++++++++++-- src/test/regress/expected/generated.out | 7 +++++++ src/test/regress/sql/generated.sql | 3 +++ 3 files changed, 23 insertions(+), 2 deletions(-) diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c index 46a383294e..7ac0edd669 100644 --- a/src/backend/catalog/heap.c +++ b/src/backend/catalog/heap.c @@ -2977,15 +2977,26 @@ check_nested_generated_walker(Node *node, void *context) AttrNumber attnum; relid = rt_fetch(var->varno, pstate->p_rtable)->relid; + if (!OidIsValid(relid)) + return false; /* XXX shouldn't we raise an error? */ + attnum = var->varattno; - if (OidIsValid(relid) && AttributeNumberIsValid(attnum) && get_attgenerated(relid, attnum)) + if (attnum > 0 && get_attgenerated(relid, attnum)) ereport(ERROR, - (errcode(ERRCODE_SYNTAX_ERROR), + (errcode(ERRCODE_INVALID_OBJECT_DEFINITION), errmsg("cannot use generated column \"%s\" in column generation expression", get_attname(relid, attnum, false)), errdetail("A generated column cannot reference another generated column."), parser_errposition(pstate, var->location))); + /* A whole-row Var is necessarily self-referential, so forbid it */ + if (attnum == 0) + ereport(ERROR, + (errcode(ERRCODE_INVALID_OBJECT_DEFINITION), + errmsg("cannot use whole-row variable in column generation expression"), + errdetail("This would cause the generated column to depend on its own value."), + parser_errposition(pstate, var->location))); + /* System columns were already checked in the parser */ return false; } diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out index 13414ed3b8..9eec3f3716 100644 --- a/src/test/regress/expected/generated.out +++ b/src/test/regress/expected/generated.out @@ -46,6 +46,13 @@ ERROR: cannot use generated column "b" in column generation expression LINE 1: ...AYS AS (a * 2) STORED, c int GENERATED ALWAYS AS (b * 3) STO... ^ DETAIL: A generated column cannot reference another generated column. +-- a whole-row var is a self-reference on steroids, so disallow that too +CREATE TABLE gtest_err_2c (a int PRIMARY KEY, + b int GENERATED ALWAYS AS (num_nulls(gtest_err_2c)) STORED); +ERROR: cannot use whole-row variable in column generation expression +LINE 2: b int GENERATED ALWAYS AS (num_nulls(gtest_err_2c)) STOR... + ^ +DETAIL: This would cause the generated column to depend on its own value. -- invalid reference CREATE TABLE gtest_err_3 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (c * 2) STORED); ERROR: column "c" does not exist diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql index ece4f66db3..9bc4f76606 100644 --- a/src/test/regress/sql/generated.sql +++ b/src/test/regress/sql/generated.sql @@ -17,6 +17,9 @@ CREATE TABLE gtest_err_1 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a * 2) S -- references to other generated columns, including self-references CREATE TABLE gtest_err_2a (a int PRIMARY KEY, b int GENERATED ALWAYS AS (b * 2) STORED); CREATE TABLE gtest_err_2b (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a * 2) STORED, c int GENERATED ALWAYS AS (b * 3) STORED); +-- a whole-row var is a self-reference on steroids, so disallow that too +CREATE TABLE gtest_err_2c (a int PRIMARY KEY, + b int GENERATED ALWAYS AS (num_nulls(gtest_err_2c)) STORED); -- invalid reference CREATE TABLE gtest_err_3 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (c * 2) STORED);