Partition Tid Scan

名称

Tid扫描算子

介绍

实现在分区表上的Tid扫描，类似于普通表的 Tid Scan。

举例

--清理环境
DROP TABLE t1;

--创建分区表
CREATE TABLE t1（a int,b int)
PARTITION BY HASH(a, b) PARTITIONS 2;

INSERT INTO t1 SELECT generate_series(1,20),generate_series(21,40);
ANALYZE t1;

--创建游标
DECLARE c1 SCROLL CURSOR FOR SELECT * FROM t1;
OPEN c1;
FETCH from c1;

EXPLAIN ANALYZE DELETE FROM t1 WHERE CURRENT OF c1;
                                              QUERY PLAN
------------------------------------------------------------------------------------------------------
 Partition Tid Scan on T1  (cost=0.00..1.01 rows=1 width=16) (actual time=0.01..0.01 rows=1 loops=1)
   Filter: (("ROWID" = 17410::bigint) AND (SYSATTR_SEGMENTID = 17088::bigint))
 Planning Time: 0.20 msec
 Execution Time: 0.18 msec
(4 rows)

CLOSE c1;

--清理环境
DEALLOCATE c1;
DROP TABLE t1 CASCADE;

• on T1 算子属性，表示Tid扫描的分区表
• Filter 限定条件