Gbase 8C - SQL reference 6 SQL syntax (13)

1. NOTIFY

Function description

Generate a notification .

Grammar format

NOTIFY channel [ , payload ]

Parameter description

1. channel： Name of the channel to signal , Can be any identifier ;
2. payload： To communicate through notification “ load ” character string , It must be a simple string , By default , The string cannot exceed 8000 byte .

matters needing attention

NOTIFY The queue is used to keep the notification information that has been sent but has not been monitored , If the queue is full （ Default 8GB）, call NOTIFY The transaction will be submitted with errors .

It has been implemented NOTIFY The transaction of cannot be prepared for two-phase commit .

You can also use functions pg_notify(text, text) Sending notice , The first parameter of this function is the channel name , The second parameter is the load .

Example

LISTEN virtual;

LISTEN

NOTIFY virtual;

NOTIFY

Asynchronous notification "virtual" received from server process with PID 2302.

NOTIFY virtual, 'This is the payload';

NOTIFY

Asynchronous notification "virtual" with payload "This is the payload" received from server process with PID 2302.

LISTEN foo;

LISTEN

SELECT pg_notify('fo' || 'o', 'pay' || 'load');

 pg_notify

-----------

(1 row)

Asynchronous notification "foo" with payload "payload" received from server process with PID 2302.

Grammar compatible

stay SQL There is no in the standard NOTIFY sentence .

Related to the grammar

LISTEN, UNLISTEN

1. PAUSE CLUSTER

Function description

Pause the database cluster .

Grammar format

PAUSE CLUSTER

matters needing attention

The pause command will organize any new things to start and wait for the existing things to complete before returning . The existing session is still connected to CN node , Just new things will not be implemented .

Pause command is used for database maintenance 、 restart DN Node and manual failover . In the suspended state, the application will not receive an error , Unless the connection times out .

When the pause ends, you can execute UNPAUSE CLUSTER command .

Example

PAUSE CLUSTER;

PAUSE CLUSTER

Grammar compatible

stay SQL There is no in the standard PAUSE CLUSTER sentence .

1. PREPARE

Function description

Create a preliminary statement .

Grammar format

PREPARE name [ ( data_type [, ...] ) ] AS statement

Parameter description

1. name： Specify the name of the prepared statement , It must be unique in this session ;
2. data_type： Data type of parameter ;
3. statement： yes SELECT INSERT、UPDATE、DELETE or VALUES One of the statements .

matters needing attention

To check PostgreSQL Query plan for a prepared statement , have access to EXPLAIN, for example EXPLAIN EXECUTE.

By querying pg_prepared_statements System view to see all available prepared statements in the session .

Example

PREPARE insert_customer(int,varchar(200),date,varchar(50)) AS INSERT INTO customer VALUES($1,$2,$3,$4);

PREPARE

EXECUTE insert_customer(11, ' d ','20200618',15974236);

INSERT 0 1

Grammar compatible

SQL The standard includes a PREPARE sentence , But it is only used for embedded SQL.

Related to the grammar

DEALLOCATE, EXECUTE

1. PREPARE TRANSACTION

Function description

Prepare for the two-phase commit of the current transaction .

Grammar format

PREPARE TRANSACTION transaction_id

Parameter description

1. transaction_id： Identifier of the transaction to be committed , Used later in COMMIT PREPARED or ROLLBACK PREPARED When identifying this transaction . The identifier must be less than 200 Byte string , And it cannot have the same name as any identifier that has been used by the current preparatory transaction .

matters needing attention

The transaction function is automatically maintained by the database , Transaction functions should not be used explicitly .

This command must be used in transactions .

All currently available ready transactions are listed in pg_prepared_xacts In the system view .

Grammar compatible

PREPARE TRANSACTION It's a kind of PostgreSQL Expand .

Related to the grammar

COMMIT PREPARED, ROLLBACK PREPARED

1. REASSIGN OWNED

Function description

Modify the owner of the database object .

REASSIGN OWNED The system is required to integrate all old_roles The owner of the owned database object is changed to new_role.

Grammar format

REASSIGN OWNED BY { old_role | CURRENT_USER | SESSION_USER } [, ...]

               TO { new_role | CURRENT_USER | SESSION_USER }

Parameter description

1. old_role： The role name of the old owner ;
2. new_role： The name of the new role that will become the owner of these objects .

matters needing attention

REASSIGN OWNED It is often used to prepare before deleting roles .

perform REASSIGN OWNED You need permissions on the original role and the target role .

Grammar compatible

REASSIGN OWNED Command is a kind of PostgreSQL Expand .

Related to the grammar

DROP OWNED, DROP ROLE, ALTER DATABASE

1. REFRESH MATERIALIZED VIEW

Function description

Replace the contents of a materialized view .

Grammar format

REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] name

    [ WITH [ NO ] DATA ]

Parameter description

1. CONCURRENTLY： Refreshing the materialized view does not block the concurrent selection on the materialized view ;
2. name： The name of the materialized view to refresh , Can be modified by patterns .

matters needing attention

nothing

Example

REFRESH MATERIALIZED VIEW mv_customer;

REFRESH MATERIALIZED VIEW

Grammar compatible

REFRESH MATERIALIZED VIEW It's a kind of PostgreSQL Expand .

Related to the grammar

CREATE MATERIALIZED VIEW, ALTER MATERIALIZED VIEW, DROP MATERIALIZED VIEW

1. REINDEX

Function description

Rebuild index .

Grammar format

REINDEX [ ( VERBOSE ) ] { INDEX | TABLE | SCHEMA | DATABASE | SYSTEM } name

Parameter description

1. INDEX： Rebuild the specified index ;
2. TABLE： Rebuild all indexes of the specified table , If the table has dependent "TOAST" surface , The table will also be indexed ;
3. SCHEMA： Rebuild all indexes of the specified schema , If the table of the mode has dependent "TOAST" surface , Then the table will also be re indexed , Indexes on shared directories will also be processed , In this case REINDEX Cannot execute within a transaction ;
4. DATABASE： Rebuild all indexes in the current database , In this case REINDEX Cannot execute within a transaction ;
5. SYSTEM： Rebuild indexes on all system tables on the current database , The index on the user table will not be processed , In this case REINDEX Cannot execute within a transaction ;
6. name： The index that needs to be rebuilt 、 surface 、 Database name , Tables and indexes can be decorated with patterns ;
7. VERBOSE： Print a progress report when each index is rebuilt .

matters needing attention

You need to use REINDEX Rebuild index ：

1. Index crash , And no longer contain valid data .
2. The index becomes “ Overstaffed ”, Contains a large number of empty pages or near empty pages .
3. Storage parameters changed for index （ For example, fill factor ）, And I hope this change will take full effect .
4. Use CONCURRENTLY Option failed to create index , Left a “ illegal ” Indexes .

Example

REINDEX INDEX customer_idx;

REINDEX

Grammar compatible

stay SQL There is no in the standard REINDEX command .

1. RESET

Function description

Restore the specified runtime parameters to the default values .

Grammar format

RESET configuration_parameter

RESET ALL

Parameter description

1. configuration_parameter： Name of the runtime parameter , have access to SHOW ALL Command to view runtime parameters ;
2. ALL： All runtime parameters .

matters needing attention

RESET Transactional behavior and SET identical ： Its impact will be reversed by transaction rollback .

Example

RESET timezone;

RESET

Grammar compatible

ESET It's a kind of PostgreSQL Expand .

Related to the grammar

SET, SHOW

1. REVOKE

Function description

Used to revoke the permissions of one or more roles .

Grammar format

REVOKE [ GRANT OPTION FOR ]

    { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES | TRIGGER }

    [, ...] | ALL [ PRIVILEGES ] }

    ON { [ TABLE ] table_name [, ...]

         | ALL TABLES IN SCHEMA schema_name [, ...] }

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { { SELECT | INSERT | UPDATE | REFERENCES } ( column_name [, ...] )

    [, ...] | ALL [ PRIVILEGES ] ( column_name [, ...] ) }

    ON [ TABLE ] table_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { { USAGE | SELECT | UPDATE }

    [, ...] | ALL [ PRIVILEGES ] }

    ON { SEQUENCE sequence_name [, ...]

         | ALL SEQUENCES IN SCHEMA schema_name [, ...] }

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...] | ALL [ PRIVILEGES ] }

    ON DATABASE database_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { USAGE | ALL [ PRIVILEGES ] }

    ON DOMAIN domain_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { USAGE | ALL [ PRIVILEGES ] }

    ON FOREIGN DATA WRAPPER fdw_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { USAGE | ALL [ PRIVILEGES ] }

    ON FOREIGN SERVER server_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { EXECUTE | ALL [ PRIVILEGES ] }

    ON { FUNCTION function_name [ ( [ [ argmode ] [ arg_name ] arg_type [, ...] ] ) ] [, ...]

         | ALL FUNCTIONS IN SCHEMA schema_name [, ...] }

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { USAGE | ALL [ PRIVILEGES ] }

    ON LANGUAGE lang_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { { SELECT | UPDATE } [, ...] | ALL [ PRIVILEGES ] }

    ON LARGE OBJECT loid [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { { CREATE | USAGE } [, ...] | ALL [ PRIVILEGES ] }

    ON SCHEMA schema_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { CREATE | ALL [ PRIVILEGES ] }

    ON TABLESPACE tablespace_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ GRANT OPTION FOR ]

    { USAGE | ALL [ PRIVILEGES ] }

    ON TYPE type_name [, ...]

    FROM { [ GROUP ] role_name | PUBLIC } [, ...]

    [ CASCADE | RESTRICT ]

REVOKE [ ADMIN OPTION FOR ]

    role_name [, ...] FROM role_name [, ...]

    [ CASCADE | RESTRICT ]

Parameter description

Permission category and parameter description , Please see the GRANT.

matters needing attention

keyword PUBLIC Represents an implicitly defined group with all roles .

The privileges that any particular role has include those directly granted to that role 、 Permissions obtained from the role that this role is a member of and granted to PUBLIC Authority . therefore , from PUBLIC Take back SELECT Privileges don't necessarily mean that all characters will lose on the object SELECT Privilege , Those roles that are granted directly or through another role will still have it . Similarly , Withdraw from a user SELECT after , If PUBLIC There is still a SELECT jurisdiction , This user can still use SELECT.

Appoint GRANT OPTION FOR when , Only revoke the authority authorized for this authority , Without revoking the permission itself .

Such as user A Have a table UPDATE jurisdiction , And WITH GRANT OPTION Options , meanwhile A Give this permission to the user B, Then the user B The permissions held are called dependent permissions . When the user A When the permission or authorization option held is revoked , Dependent permissions still exist , But if it's stated CASCADE, Then all dependent permissions are revoked .

A user can only revoke the permissions directly granted by itself . for example , If the user A Be designated to authorize （WITHADMIN OPTION） Options , And give a permission to the user B, And then the user B It also gives users C, Then the user A Can't directly C Revocation of authority . however , user A Users can be revoked B Authorization options , And use CASCADE. such , user C Your permission will be automatically revoked . Another example ： If A and B It's all given to C Same permissions , be A Can revoke his own authorization options , But it cannot be revoked B Of , therefore C Still have this permission .

If you execute REVOKE The permissions held by the role of are obtained through multi-level membership , It is uncertain which included role executes the command . On this occasion , The best way is to use SET ROLE Become a specific role , And then execute REVOKE, Otherwise, permissions that you don't want to delete may be deleted , Or there is no permission to delete .

Example

REVOKE INSERT ON g_c1 FROM PUBLIC;

REVOKE

Grammar compatible

This command is partially compatible SQL.

Related to the grammar

GRANT

1. ROLLBACK

Function description

Rollback the current transaction and cancel all updates in the current transaction .

Grammar format

ROLLBACK [ WORK | TRANSACTION ]

Parameter description

1. WORK | TRANSACTION： Optional keywords , In addition to increasing readability , There's no other effect .

matters needing attention

If not issued within a transaction ROLLBACK There will be no problem , But a warning message will be thrown .

Example

BEGIN;

BEGIN

ROLLBACK;

ROLLBACK

Grammar compatible

SQL The standard only specifies ROLLBACK and ROLLBACK WORK Two forms . besides , This command is completely up to standard .

Related to the grammar

BEGIN, COMMIT, END, ROLLBACK TO SAVEPOINT