From 003e9b6b6e3429de0910d01ff6840f4bf0f362c8 Mon Sep 17 00:00:00 2001 From: jian he Date: Mon, 19 May 2025 14:14:28 +0800 Subject: [PATCH v5 3/3] fast default for domain with constraints MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is primarily done by evaluating CoerceToDomain with soft error support. If CoerceToDomain is evaluated as false in ATExecAddColumn, the defval node's value cannot be cast to the domain type. However, in some cases like when the table is empty, we cannot explicitly error out in ATExecAddColumn (Phase 2). For example, imagine add a new domain column to empty x, and the column domain specification is ``CHECK(value > 10) DEFAULT 8``.  In such situations, the ALTER TABLE ADD COLUMN should be success. Thanks to commit aaaf9449ec6be62cb0d30ed3588dc384f56274bf[1], ExprState.escontext (ErrorSaveContext) was added, and ExecEvalConstraintNotNull, ExecEvalConstraintCheck were changed to use errsave instead of hard error. Now we can evaluate CoerceToDomain in a soft error way. However we do table rewrite for domain with volatile check constraints. discussion: https://postgr.es/m/CACJufxE_+iZBR1i49k_AHigppPwLTJi6km8NOsC7FWvKdEmmXg@mail.gmail.com [1]: https://git.postgresql.org/cgit/postgresql.git/commit/?id=aaaf9449ec6be62cb0d30ed3588dc384f56274bf --- src/backend/commands/tablecmds.c | 45 +++++++++++------- src/test/regress/expected/fast_default.out | 55 ++++++++++++++++++++++ src/test/regress/sql/fast_default.sql | 44 +++++++++++++++++ 3 files changed, 128 insertions(+), 16 deletions(-) diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 54ad38247aa..dba2ea77cad 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -7429,15 +7429,6 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel, * NULL if so, so without any modification of the tuple data we will get * the effect of NULL values in the new column. * - * An exception occurs when the new column is of a domain type: the domain - * might have a not-null constraint, or a check constraint that indirectly - * rejects nulls. If there are any domain constraints then we construct - * an explicit NULL default value that will be passed through - * CoerceToDomain processing. (This is a tad inefficient, since it causes - * rewriting the table which we really wouldn't have to do; but we do it - * to preserve the historical behavior that such a failure will be raised - * only if the table currently contains some rows.) - * * Note: we use build_column_default, and not just the cooked default * returned by AddRelationNewConstraints, so that the right thing happens * when a datatype's default applies. @@ -7456,6 +7447,7 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel, { bool has_domain_constraints; bool has_missing = false; + bool has_volatile = false; /* * For an identity column, we can't use build_column_default(), @@ -7473,8 +7465,17 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel, else defval = (Expr *) build_column_default(rel, attribute->attnum); + has_domain_constraints = DomainHaveVolatileConstraints(attribute->atttypid, &has_volatile); + /* + * Adding column with volatile domain constraint requires table rewrite + */ + if (has_volatile) + { + Assert(has_domain_constraints); + tab->rewrite |= AT_REWRITE_DEFAULT_VAL; + } + /* Build CoerceToDomain(NULL) expression if needed */ - has_domain_constraints = DomainHasConstraints(attribute->atttypid); if (!defval && has_domain_constraints) { Oid baseTypeId; @@ -7516,14 +7517,18 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel, * Attempt to skip a complete table rewrite by storing the * specified DEFAULT value outside of the heap. This is only * allowed for plain relations and non-generated columns, and the - * default expression can't be volatile (stable is OK). Note that - * contain_volatile_functions deems CoerceToDomain immutable, but - * here we consider that coercion to a domain with constraints is - * volatile; else it might fail even when the table is empty. + * default expression can't be volatile (stable is OK), and the + * domain constraint can't be volatile (stable is OK). + * + * Note that contain_volatile_functions deems CoerceToDomain + * immutable. However we have computed CoerceToDomain is volatile + * or not via DomainHaveVolatileConstraints. We use soft error + * evaluation of CoerceToDomain, if evaluation failed, then set + * table rewrite to true. */ if (rel->rd_rel->relkind == RELKIND_RELATION && !colDef->generated && - !has_domain_constraints && + !has_volatile && !contain_volatile_functions((Node *) defval)) { EState *estate; @@ -7533,10 +7538,18 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel, /* Evaluate the default expression */ estate = CreateExecutorState(); - exprState = ExecPrepareExpr(defval, estate); + exprState = ExecPrepareExprSafe(defval, estate); + missingval = ExecEvalExpr(exprState, GetPerTupleExprContext(estate), &missingIsNull); + + if (SOFT_ERROR_OCCURRED(exprState->escontext)) + { + missingIsNull = true; + tab->rewrite |= AT_REWRITE_DEFAULT_VAL; + } + /* If it turns out NULL, nothing to do; else store it */ if (!missingIsNull) { diff --git a/src/test/regress/expected/fast_default.out b/src/test/regress/expected/fast_default.out index ccbcdf8403f..861208a269a 100644 --- a/src/test/regress/expected/fast_default.out +++ b/src/test/regress/expected/fast_default.out @@ -317,11 +317,66 @@ SELECT a, b, length(c) = 3 as c_ok, d, e >= 10 as e_ok FROM t2; 2 | 3 | t | {This,is,abcd,the,real,world} | t (2 rows) +---test fast default over domains with constraints +CREATE DOMAIN domain5 AS int check(value > 10) default 8; +CREATE DOMAIN domain6 as int not null; +CREATE DOMAIN domain7 as int check(value > 10) DEFAULT random(min=>10, max=>100); +CREATE DOMAIN domain8 as int check((value + random(min=>11::int, max=>11)) > 12); +--tests with empty table. +CREATE TABLE t3(a int); +ALTER TABLE t3 ADD COLUMN b domain5 default 1; --ok, table rewrite +NOTICE: rewriting table t3 for reason 2 +ALTER TABLE t3 ADD COLUMN c domain6 default 11 + NULL; --ok, table rewrite +NOTICE: rewriting table t3 for reason 2 +ALTER TABLE t3 ADD COLUMN d domain7 default 2; --ok, table rewrite +NOTICE: rewriting table t3 for reason 2 +ALTER TABLE t3 ADD COLUMN e domain8 default 3; --ok, table rewrite +NOTICE: rewriting table t3 for reason 2 +DROP TABLE t3; +--tests with non-empty table. +CREATE TABLE t3(a int); +INSERT INTO t3 VALUES(1),(2); +ALTER TABLE t3 ADD COLUMN b domain5; --table rewrite, then fail +NOTICE: rewriting table t3 for reason 2 +ERROR: value for domain domain5 violates check constraint "domain5_check" +ALTER TABLE t3 ADD COLUMN b domain6; --table rewrite, then fail +NOTICE: rewriting table t3 for reason 2 +ERROR: domain domain6 does not allow null values +ALTER TABLE t3 ADD COLUMN b domain5 default 12; --no table rewrite +ALTER TABLE t3 ADD COLUMN c domain6 default 13; --no table rewrite +--no table rewrite. explicit column default expression override domain default +--expression +ALTER TABLE t3 ADD COLUMN d domain7 default 15; +SELECT attnum, attname, atthasmissing, atthasdef, attmissingval +FROM pg_attribute +WHERE attnum > 0 AND attrelid = 't3'::regclass AND attisdropped is false +AND atthasmissing +ORDER BY attnum; + attnum | attname | atthasmissing | atthasdef | attmissingval +--------+---------+---------------+-----------+--------------- + 2 | b | t | t | {12} + 3 | c | t | t | {13} + 4 | d | t | t | {15} +(3 rows) + +--table rewrite. we are applying domain volatile default expresion +ALTER TABLE t3 ADD COLUMN e domain7; +NOTICE: rewriting table t3 for reason 2 +--table rewrite for volatile domain constraints. +ALTER TABLE t3 ADD COLUMN f domain8 default 14; --table rewrite +NOTICE: rewriting table t3 for reason 2 +ALTER TABLE t3 ADD COLUMN f1 domain8; --table rewrite +NOTICE: rewriting table t3 for reason 2 DROP TABLE t2; +DROP TABLE t3; DROP DOMAIN domain1; DROP DOMAIN domain2; DROP DOMAIN domain3; DROP DOMAIN domain4; +DROP DOMAIN domain5; +DROP DOMAIN domain6; +DROP DOMAIN domain7; +DROP DOMAIN domain8; DROP FUNCTION foo(INT); -- Fall back to full rewrite for volatile expressions CREATE TABLE T(pk INT NOT NULL PRIMARY KEY); diff --git a/src/test/regress/sql/fast_default.sql b/src/test/regress/sql/fast_default.sql index 068dd0bc8aa..a98d86a6204 100644 --- a/src/test/regress/sql/fast_default.sql +++ b/src/test/regress/sql/fast_default.sql @@ -287,11 +287,55 @@ ORDER BY attnum; SELECT a, b, length(c) = 3 as c_ok, d, e >= 10 as e_ok FROM t2; +---test fast default over domains with constraints +CREATE DOMAIN domain5 AS int check(value > 10) default 8; +CREATE DOMAIN domain6 as int not null; +CREATE DOMAIN domain7 as int check(value > 10) DEFAULT random(min=>10, max=>100); +CREATE DOMAIN domain8 as int check((value + random(min=>11::int, max=>11)) > 12); + +--tests with empty table. +CREATE TABLE t3(a int); +ALTER TABLE t3 ADD COLUMN b domain5 default 1; --ok, table rewrite +ALTER TABLE t3 ADD COLUMN c domain6 default 11 + NULL; --ok, table rewrite +ALTER TABLE t3 ADD COLUMN d domain7 default 2; --ok, table rewrite +ALTER TABLE t3 ADD COLUMN e domain8 default 3; --ok, table rewrite +DROP TABLE t3; + +--tests with non-empty table. +CREATE TABLE t3(a int); +INSERT INTO t3 VALUES(1),(2); + +ALTER TABLE t3 ADD COLUMN b domain5; --table rewrite, then fail +ALTER TABLE t3 ADD COLUMN b domain6; --table rewrite, then fail +ALTER TABLE t3 ADD COLUMN b domain5 default 12; --no table rewrite +ALTER TABLE t3 ADD COLUMN c domain6 default 13; --no table rewrite +--no table rewrite. explicit column default expression override domain default +--expression +ALTER TABLE t3 ADD COLUMN d domain7 default 15; + +SELECT attnum, attname, atthasmissing, atthasdef, attmissingval +FROM pg_attribute +WHERE attnum > 0 AND attrelid = 't3'::regclass AND attisdropped is false +AND atthasmissing +ORDER BY attnum; + +--table rewrite. we are applying domain volatile default expresion +ALTER TABLE t3 ADD COLUMN e domain7; + +--table rewrite for volatile domain constraints. +ALTER TABLE t3 ADD COLUMN f domain8 default 14; --table rewrite +ALTER TABLE t3 ADD COLUMN f1 domain8; --table rewrite + DROP TABLE t2; +DROP TABLE t3; DROP DOMAIN domain1; DROP DOMAIN domain2; DROP DOMAIN domain3; DROP DOMAIN domain4; +DROP DOMAIN domain5; +DROP DOMAIN domain6; +DROP DOMAIN domain7; +DROP DOMAIN domain8; DROP FUNCTION foo(INT); -- Fall back to full rewrite for volatile expressions -- 2.34.1