模糊查询or导致索引失效

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表结构

-- ----------------------------
-- Table structure for t_test
-- ----------------------------
DROP TABLE IF EXISTS "public"."t_test";
CREATE TABLE "public"."t_test" (
  "id" int4 NOT NULL,
  "name" varchar(50) COLLATE "pg_catalog"."default",
  "desc" varchar(50) COLLATE "pg_catalog"."default",
  "age" int4,
  "sort" int4
)
;
-- ----------------------------
-- Indexes structure for table t_test
-- ----------------------------
CREATE INDEX "idx_test_age" ON "public"."t_test" USING btree (
  "age" "pg_catalog"."int4_ops" ASC NULLS LAST
);
CREATE INDEX "idx_test_name" ON "public"."t_test" USING btree (
  "name" COLLATE "pg_catalog"."default" "pg_catalog"."text_ops" ASC NULLS LAST
);
-- ----------------------------
-- Primary Key structure for table t_test
-- ----------------------------
ALTER TABLE "public"."t_test" ADD CONSTRAINT "t_test_pkey" PRIMARY KEY ("id");

插入测试数据

插入100000条测试数据

验证

explain SELECT * FROM "t_test" where age= 25;

explain SELECT * FROM "t_test" where name like '%张三1%' or age= 25;

explain SELECT * FROM "t_test" where age= 25 or name like '%张三1%';

explain analyse SELECT * FROM "t_test" where age= 25
union
SELECT * FROM "t_test" where name like '%张三1%';

​​

结论

pgsql中or条件中只要有一个条件存在前模糊都会破坏索引的使用

优化

用union去组合非索引破坏索引条件的条件

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