我有table

CREATE TABLE IF NOT EXISTS employeedb.employee_tbl
(
    id                         integer                  NOT NULL GENERATED ALWAYS AS IDENTITY ( INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1 ),
    dm_company_id              integer                  NOT NULL,
    customer_employee_id       text                     NOT NULL),
    personal_mobile            text,
    CONSTRAINT employee_pkey PRIMARY KEY (id),
    CONSTRAINT employee_id_company_constraint UNIQUE (dm_company_id, customer_employee_id)

和索引上personal_移动的类

CREATE INDEX company_id_personal_mobile_index ON employeedb.employee_tbl (dm_company_id, personal_mobile COLLATE "C");

现在当我点击以下查询时

explain analyse select * from employeedb.employee_tbl where dm_company_id = 2011 and employee_tbl.personal_mobile like '+1%';

我总是看到使用employee_id_company_constraint索引。

Index Scan using employee_id_company_constraint on employee_tbl  (cost=0.14..8.16 rows=1 width=641) (actual time=0.056..0.093 rows=2 loops=1)
  Index Cond: (dm_company_id = 2011)
  Filter: (personal_mobile ~~ '+1%'::text)
  Rows Removed by Filter: 28
Planning Time: 0.951 ms
Execution Time: 0.173 ms

为什么Postgres不使用比employee_id_company_constraint更高效的company_id_personal_mobile_index来进行上述查询？