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Reduce lock level for ALTER DOMAIN ... VALIDATE CONSTRAINT

author Peter Eisentraut <peter@eisentraut.org>

2025年8月22日 06:51:29 +0000 (08:51 +0200)

committer Peter Eisentraut <peter@eisentraut.org>

2025年8月22日 06:56:11 +0000 (08:56 +0200)

Reduce from ShareLock to ShareUpdateExclusivelock. Validation during
ALTER DOMAIN ... ADD CONSTRAINT keeps using ShareLock.

Example:

create domain d1 as int;
create table t (a d1);
alter domain d1 add constraint cc10 check (value > 10) not valid;

begin;
alter domain d1 validate constraint cc10;

-- another session
insert into t values (8);

Now we should still be able to perform DML operations on table t while
the domain constraint is being validated. The equivalent works
already on table constraints.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CACJufxHz92A88NLRTA2msgE2dpXpE-EoZ2QO61od76-6bfqurA%40mail.gmail.com

src/backend/commands/typecmds.c patch | blob | blame | history

diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c

index 26d985193aea42888c250b977cdc2f0d5e91fd75..c6de04819f1747aa987097ac52ea9515550cae75 100644 (file)

--- a/src/backend/commands/typecmds.c

+++ b/src/backend/commands/typecmds.c

@@ -126,7 +126,7 @@ static Oid findTypeSubscriptingFunction(List *procname, Oid typeOid);

static Oid findRangeSubOpclass(List *opcname, Oid subtype);

static Oid findRangeCanonicalFunction(List *procname, Oid typeOid);

static Oid findRangeSubtypeDiffFunction(List *procname, Oid subtype);

-static void validateDomainCheckConstraint(Oid domainoid, const char *ccbin);

+static void validateDomainCheckConstraint(Oid domainoid, const char *ccbin, LOCKMODE lockmode);

static void validateDomainNotNullConstraint(Oid domainoid);

static List *get_rels_with_domain(Oid domainOid, LOCKMODE lockmode);

static void checkEnumOwner(HeapTuple tup);

@@ -2986,7 +2986,7 @@ AlterDomainAddConstraint(List *names, Node *newConstraint,

* to.

if (!constr->skip_validation)

- validateDomainCheckConstraint(domainoid, ccbin);

+ validateDomainCheckConstraint(domainoid, ccbin, ShareLock);

* We must send out an sinval message for the domain, to ensure that

@@ -3098,7 +3098,12 @@ AlterDomainValidateConstraint(List *names, const char *constrName)

val = SysCacheGetAttrNotNull(CONSTROID, tuple, Anum_pg_constraint_conbin);

conbin = TextDatumGetCString(val);

- validateDomainCheckConstraint(domainoid, conbin);

+ /*

+ * Locking related relations with ShareUpdateExclusiveLock is ok because

+ * not-yet-valid constraints are still enforced against concurrent inserts

+ * or updates.

+ */

+ validateDomainCheckConstraint(domainoid, conbin, ShareUpdateExclusiveLock);

* Now update the catalog, while we have the door open.

@@ -3191,9 +3196,16 @@ validateDomainNotNullConstraint(Oid domainoid)

* Verify that all columns currently using the domain satisfy the given check

* constraint expression.

+ *

+ * It is used to validate existing constraints and to add newly created check

+ * constraints to a domain.

+ *

+ * The lockmode is used for relations using the domain. It should be

+ * ShareLock when adding a new constraint to domain. It can be

+ * ShareUpdateExclusiveLock when validating an existing constraint.

static void

-validateDomainCheckConstraint(Oid domainoid, const char *ccbin)

+validateDomainCheckConstraint(Oid domainoid, const char *ccbin, LOCKMODE lockmode)

{

Expr *expr = (Expr *) stringToNode(ccbin);

List *rels;

@@ -3210,9 +3222,7 @@ validateDomainCheckConstraint(Oid domainoid, const char *ccbin)

exprstate = ExecPrepareExpr(expr, estate);

/* Fetch relation list with attributes based on this domain */

- /* ShareLock is sufficient to prevent concurrent data changes */

- rels = get_rels_with_domain(domainoid, ShareLock);

+ rels = get_rels_with_domain(domainoid, lockmode);

foreach(rt, rels)

{

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