忽略重复插入的最佳方法？ [重复]

  -- Ignores duplicates.
  INSERT INTO
    db_table (tbl_column_1, tbl_column_2)
  VALUES (
    SELECT
      unnseted_column,
      param_association
    FROM
      unnest( param_array_ids ) AS unnested_column
  );

  BEGIN
    INSERT INTO db_table (tbl_column) VALUES (v_tbl_column);
  EXCEPTION WHEN unique_violation THEN
    -- Ignore duplicate inserts.
  END;

CREATE OR REPLACE RULE db_table_ignore_duplicate_inserts AS
    ON INSERT TO db_table
   WHERE (EXISTS ( SELECT 1
           FROM db_table
          WHERE db_table.tbl_column = NEW.tbl_column)) DO INSTEAD NOTHING;

#1 楼

作为另一个问题的答案（此问题被视为重复），提到了（自9.5版起）本机UPSERT功能。对于较旧的版本，请继续阅读:)

我已经建立了一个检查选项的测试。我将包含以下代码，该代码可以在Linux / Unix机壳上的psql中运行（因为为了使结果更清晰，我将设置命令的输出通过管道传输到/dev/null-在Windows机壳上，可以选择而是一个日志文件）。

我试图通过在INSERT存储过程内的循环中使用每种类型使用多个（即100个）plpgsql来使不同的结果具有可比性。此外，在每次运行之前，都会通过截断并重新插入原始数据来重置表。

检查一些测试运行，看起来就像使用规则并显式添加WHERE NOT EXISTS或INSERT语句花费相似的时间，而处理异常则需要花费更多的时间才能完成。

后者并不奇怪：没有一个块。因此，不要
不需要使用EXCEPTION。


就个人而言，由于其可读性和可维护性，我更喜欢在WHERE NOT EXISTS自身中添加INSERT位。就像使用触发器（也可以在此处进行测试）一样，使用存在的规则进行调试（或简单地跟踪INSERT行为）也会变得更加复杂。问题）：

\o /dev/null
\timing off

-- set up data
DROP TABLE IF EXISTS insert_test;

CREATE TABLE insert_test_base_data (
    id integer PRIMARY KEY,
    col1 double precision,
    col2 text
);

CREATE TABLE insert_test (
    id integer PRIMARY KEY,
    col1 double precision,
    col2 text
);

INSERT INTO insert_test_base_data
SELECT i, (SELECT random() AS r WHERE s.i = s.i)
FROM 
    generate_series(2, 200, 2) s(i)
;

UPDATE insert_test_base_data
SET col2 = md5(col1::text)
;

INSERT INTO insert_test
SELECT *
FROM insert_test_base_data
;



-- function with exception block to be called later
CREATE OR REPLACE FUNCTION f_insert_test_insert(
    id integer,
    col1 double precision,
    col2 text
)
RETURNS void AS
$body$
BEGIN
    INSERT INTO insert_test
    VALUES (, , )
    ;
EXCEPTION
    WHEN unique_violation
    THEN NULL;
END;
$body$
LANGUAGE plpgsql;



-- function running plain SQL ... WHERE NOT EXISTS ...
CREATE OR REPLACE FUNCTION insert_test_where_not_exists()
RETURNS void AS
$body$
BEGIN
    FOR i IN 1 .. 100
    LOOP
        INSERT INTO insert_test
        SELECT i, rnd, md5(rnd::text)
        FROM (SELECT random() AS rnd) r
        WHERE NOT EXISTS (
            SELECT 1
            FROM insert_test
            WHERE id = i
        )
        ;
    END LOOP;
END;
$body$
LANGUAGE plpgsql;



-- call a function with exception block
CREATE OR REPLACE FUNCTION insert_test_function_with_exception_block()
RETURNS void AS
$body$
BEGIN
    FOR i IN 1 .. 100
    LOOP
        PERFORM f_insert_test_insert(i, rnd, md5(rnd::text))
        FROM (SELECT random() AS rnd) r
        ;
    END LOOP;
END;
$body$
LANGUAGE plpgsql;



-- leave checking existence to a rule
CREATE OR REPLACE FUNCTION insert_test_rule()
RETURNS void AS
$body$
BEGIN
    FOR i IN 1 .. 100
    LOOP
        INSERT INTO insert_test
        SELECT i, rnd, md5(rnd::text)
        FROM (SELECT random() AS rnd) r
        ;
    END LOOP;
END;
$body$
LANGUAGE plpgsql;



\o
\timing on


\echo 
\echo 'check before INSERT'

SELECT insert_test_where_not_exists();

\echo 



\o /dev/null

\timing off

TRUNCATE insert_test;

INSERT INTO insert_test
SELECT *
FROM insert_test_base_data
;

\timing on

\o

\echo 'catch unique-violation'

SELECT insert_test_function_with_exception_block();

\echo 
\echo 'implementing a RULE'

\o /dev/null
\timing off

TRUNCATE insert_test;

INSERT INTO insert_test
SELECT *
FROM insert_test_base_data
;

CREATE OR REPLACE RULE db_table_ignore_duplicate_inserts AS
    ON INSERT TO insert_test
    WHERE EXISTS ( 
        SELECT 1
        FROM insert_test
        WHERE id = NEW.id
    ) 
    DO INSTEAD NOTHING;

\o 
\timing on

SELECT insert_test_rule();