Locks

qb includes a few methods to help you lock certain rows when executing select statements.

Note: For locks to work properly, they must be nested inside a transaction. qb does not handle any of the transaction lifecycle for you.

sharedLock

Name

Type

Required

Default

Description

No arguments

A shared lock prevents the selected rows from being modified until your transaction is committed.

QueryBuilder
QueryBuilder
query.from( "users" )
.where( "id", 1 )
.sharedLock();
MySQL
SQL Server
Postgres
Oracle
MySQL
SELECT *
FROM `users`
WHERE `id` = ?
LOCK IN SHARE MODE
SQL Server
SELECT *
FROM [users] WITH (ROWLOCK,HOLDLOCK)
WHERE [id] = ?
Postgres
SELECT *
FROM "users"
WHERE "id" = ?
FOR SHARE
Oracle
LOCK TABLE "USERS"
IN SHARE MODE NOWAIT;
SELECT *
FROM "USERS"
WHERE "ID" = ?

lockForUpdate

Name

Type

Required

Default

Description

No arguments

A lock for update lock prevents the selected rows from being modified or selected with another shared lock until your transaction is committed.

The main difference between a sharedLock and lockForUpdate is that a lockForUpdate prevents other reads or selects as well as updates.

QueryBuilder
QueryBuilder
query.from( "users" )
.where( "id", 1 )
.lockForUpdate();
MySQL
SQL Server
Postgres
Oracle
MySQL
SELECT *
FROM `users`
WHERE `id` = ?
FOR UPDATE
SQL Server
SELECT *
FROM [users] WITH (ROWLOCK,UPDLOCK,HOLDLOCK)
WHERE [id] = ?
Postgres
SELECT *
FROM "users"
WHERE "id" = ?
FOR UPDATE
Oracle
LOCK TABLE "USERS"
IN ROW EXCLUSIVE MODE NOWAIT;
SELECT *
FROM "USERS"
WHERE "ID" = ?

noLock

Name

Type

Required

Default

Description

No arguments

noLock will instruct your grammar to ignore any shared locks when executing the query.

Currently this only makes a difference in SQL Server grammars.

QueryBuilder
QueryBuilder
query.from( "users" )
.where( "id", 1 )
.noLock();
SQL Server
SQL Server
SELECT *
FROM [users] WITH (NOLOCK)
WHERE [id] = ?

lock

Name

Type

Required

Default

Description

value

string

true

The custom lock directive to add to the query.

The lock method will allow you to add a custom lock directive to your query. Think of it as the raw method for lock directives.

These lock directives vary from grammar to grammar.

clearLock

Name

Type

Required

Default

Description

No arguments

Clears any lock directive on the query.