Incremental Materialized View ​

Overview ​

Fast-refresh materialized views can be incrementally refreshed. You need to manually execute statements to incrementally refresh materialized views in a period of time. The difference between the incremental and the complete-refresh materialized views is that the fast-refresh materialized view supports only a small number of scenarios. Currently, only base table scanning statements or UNION ALL can be used to create materialized views.

Usage ​

Syntax ​

• Create a fast-refresh materialized view.

  CREATE INCREMENTAL MATERIALIZED VIEW [ view_name ] AS { query_block };

• Fullly refresh a materialized view.

  REFRESH MATERIALIZED VIEW [ view_name ];

• Incrementally refresh a materialized view.

  REFRESH INCREMENTAL MATERIALIZED VIEW [ view_name ];

• Delete a materialized view.

  DROP MATERIALIZED VIEW [ view_name ];

• Query a materialized view.

  SELECT * FROM [ view_name ];

Examples ​

-- Prepare data.
openGauss=# CREATE TABLE t1(c1 int, c2 int);
openGauss=# INSERT INTO t1 VALUES(1, 1);
openGauss=# INSERT INTO t1 VALUES(2, 2);

-- Create an fast-refresh materialized view.
openGauss=# CREATE INCREMENTAL MATERIALIZED VIEW mv AS SELECT * FROM t1;
CREATE MATERIALIZED VIEW

-- Insert data.
openGauss=# INSERT INTO t1 VALUES(3, 3);
INSERT 0 1

-- Incrementally refresh a materialized view.
openGauss=# REFRESH INCREMENTAL MATERIALIZED VIEW mv;
REFRESH MATERIALIZED VIEW

-- Query the materialized view result.
openGauss=# SELECT * FROM mv;
 c1 | c2 
----+----
  1 |  1
  2 |  2
  3 |  3
(3 rows)

-- Insert data.
openGauss=# INSERT INTO t1 VALUES(4, 4);
INSERT 0 1

-- Fullly refresh a materialized view.
openGauss=# REFRESH MATERIALIZED VIEW mv;
REFRESH MATERIALIZED VIEW

-- Query the materialized view result.
openGauss=# select * from mv;
 c1 | c2 
----+----
  1 |  1
  2 |  2
  3 |  3
  4 |  4
(4 rows)

-- Delete a materialized view.
openGauss=# DROP MATERIALIZED VIEW mv;
DROP MATERIALIZED VIEW

Support and Constraints ​

Supported Scenarios ​

• Supports statements for querying a single table.
• Supports UNION ALL for querying multiple single tables.
• Supports index creation in materialized views.
• Supports the Analyze operation in materialized views.

Unsupported Scenarios ​

• Multi-table join plans and subquery plans are not supported in materialized views.
• Except for a few ALTER operations, most DDL operations cannot be performed on base tables in materialized views.
• Materialized views cannot be added, deleted, or modified. They support only query statements.
• The temporary table, hashbucket, unlog, or partitioned table cannot be used to create materialized views.
• Materialized views cannot be created in nested mode (that is, a materialized view cannot be created in another materialized view).
• The column-store tables are not supported. Only row-store tables are supported.
• Materialized views of the UNLOGGED type are not supported, and the WITH syntax is not supported.

Constraints ​

If the materialized view definition is UNION ALL, each subquery needs to use a different base table.