• PostgreSQL应用相关问题解决


    PostgreSQL中是否区分聚簇索引与非聚簇索引的问题?

    答:PostgreSQL中区分聚簇索引与非聚簇索引。

    示例如下:

    创建聚族索引:

    CREATE INDEX test_ind

       ON yy (name ASC NULLS LAST);

    ALTER TABLE yy

      CLUSTER ON test_ind;

    创建非聚族索引:

    CREATE INDEX test_uncluster_index

       ON yy (name ASC NULLS LAST);

    临时表被删除,临时表的索引是否也被删除?

    答:临时表被删除,临时表的索引也同时被删除。

    示例如下:

    创建两个临时表:
    test1=# create temporary table tmp_t1(id int primary key,note text);
    CREATE TABLE
    test1=# dt
    List of relations
    Schema | Name | Type | Owner
    ----------------------+---------
    pg_temp_2 | tmp_t1 | table | postgres
    public | student | table | postgres
    public | testdb | table | postgres
    (3 rows)

    test1=# create temporary table tmp_t2(id int primary key,name char(10),note text);
    CREATE TABLE
    test1=# dt
    List of relations
    Schema | Name | Type | Owner
    ----------------------+---------
    pg_temp_2 | tmp_t1 | table | postgres
    pg_temp_2 | tmp_t2 | table | postgres
    public | student | table | postgres
    public | testdb | table | postgres
    (4 rows)
    给两个临时表分别创建索引并查看索引:
    test1=# create index idx_tmp_t1_id on tmp_t1(id);
    CREATE INDEX
    test1=# create index idx_tmp_t2_id on tmp_t2(id);
    CREATE INDEX
    test1=# di
    List of relations
    Schema | Name | Type | Owner | Table
    -------------------------------------------
    pg_temp_2 | idx_tmp_t1_id | index | postgres | tmp_t1
    pg_temp_2 | idx_tmp_t2_id | index | postgres | tmp_t2
    pg_temp_2 | tmp_t1_pkey | index | postgres | tmp_t1
    pg_temp_2 | tmp_t2_pkey | index | postgres | tmp_t2
    (4 rows)
    删除临时表1:
    test1=# drop table tmp_t1;
    DROP TABLE
    test1=# dt
    List of relations
    Schema | Name | Type | Owner
    ----------------------+---------
    pg_temp_2 | tmp_t2 | table | postgres
    public | student | table | postgres
    public | testdb | table | postgres
    (3 rows)
    查看索引,临时表1的索引也被删除:
    test1=# di
    List of relations
    Schema | Name | Type | Owner | Table
    -------------------------------------------
    pg_temp_2 | idx_tmp_t2_id | index | postgres | tmp_t2
    pg_temp_2 | tmp_t2_pkey | index | postgres | tmp_t2
    (2 rows)

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  • 原文地址:https://www.cnblogs.com/songyuejie/p/4877834.html
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