SHRINK ​

Function ​

Shrinks chunks in a specified compressed table to facilitate page read and write.

Precautions ​

• The shrink operation is performed only on the primary node and cannot be manually performed on the standby node.
• The shrink operation time is related to the current CPU usage and table size.
• Shrink is an optimization operation. If the database is abnormal during optimization, the optimization will not continue after the database is restarted.

Syntax ​

SHRINK TABLE table_name [nowait];
SHRINK INDEX index_name [nowait];

Parameter Description ​

• nowait

  Indicates that a task is returned immediately after being initiated without waiting for the sorting result. The daemon thread periodically wakes up to sort the tasks added by shrink.

Example ​

The following uses SHRINK TABLE as an example. The operation of SHRINK INDEX is the same as that of SHRINK TABLE.

--Create the row_compression table.
openGauss=# CREATE TABLE row_compression
(
    id int
) with (compresstype=2, compress_chunk_size = 512, compress_level = 1);

--Insert data.
openGauss=# Insert into row_compression select generate_series(1,1000);

--View data.
openGauss=# SELECT * FROM row_compression;

--Shrink the table.
openGauss=# SHRINK TABLE row_compression;

--Delete the table.
openGauss=# DROP TABLE row_compression;