savepoint(7) - BetterMan

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NAME

SAVEPOINT - define a new savepoint within the current transaction

SYNOPSIS

bash

SAVEPOINT \nsavepoint_name

DESCRIPTION

SAVEPOINT establishes a new savepoint within the current transaction.

A savepoint is a special mark inside a transaction that allows all commands that are executed after it was established to be rolled back, restoring the transaction state to what it was at the time of the savepoint.

PARAMETERS

savepoint_name

NOTES

Use ROLLBACK TO to rollback to a savepoint. Use RELEASE SAVEPOINT to destroy a savepoint, keeping the effects of commands executed after it was established.

Savepoints can only be established when inside a transaction block. There can be multiple savepoints defined within a transaction.

EXAMPLES

To establish a savepoint and later undo the effects of all commands executed after it was established:

bash

BEGIN;
\n
    INSERT INTO table1 VALUES (1);
\n
    SAVEPOINT my_savepoint;
\n
    INSERT INTO table1 VALUES (2);
\n
    ROLLBACK TO SAVEPOINT my_savepoint;
\n
    INSERT INTO table1 VALUES (3);
COMMIT;

The above transaction will insert the values 1 and 3, but not 2.

To establish and later destroy a savepoint:

bash

BEGIN;
\n
    INSERT INTO table1 VALUES (3);
\n
    SAVEPOINT my_savepoint;
\n
    INSERT INTO table1 VALUES (4);
\n
    RELEASE SAVEPOINT my_savepoint;
COMMIT;

The above transaction will insert both 3 and 4.

To use a single savepoint name:

bash

BEGIN;
\n
    INSERT INTO table1 VALUES (1);
\n
    SAVEPOINT my_savepoint;
\n
    INSERT INTO table1 VALUES (2);
\n
    SAVEPOINT my_savepoint;
\n
    INSERT INTO table1 VALUES (3);
\n
    -- rollback to the second savepoint
\n
    ROLLBACK TO SAVEPOINT my_savepoint;
\n
    SELECT * FROM table1;               -- shows rows 1 and 2
\n
    -- release the second savepoint
\n
    RELEASE SAVEPOINT my_savepoint;
\n
    -- rollback to the first savepoint
\n
    ROLLBACK TO SAVEPOINT my_savepoint;
\n
    SELECT * FROM table1;               -- shows only row 1
COMMIT;

The above transaction shows row 3 being rolled back first, then row 2.

COMPATIBILITY

SQL requires a savepoint to be destroyed automatically when another savepoint with the same name is established. In PostgreSQL, the old savepoint is kept, though only the more recent one will be used when rolling back or releasing. (Releasing the newer savepoint with RELEASE SAVEPOINT will cause the older one to again become accessible to ROLLBACK TO SAVEPOINT and RELEASE SAVEPOINT.) Otherwise, SAVEPOINT is fully SQL conforming.