如何從執行的預准備語句中獲取$ 1參數的值（使用current_query（）在觸發器內）

Question

在觸發器中我想看看sql查詢觸發了這個觸發器。 我使用了postgresql（8.4）的current_query（）函數。

一切都很好，但是如果觸發器是由准備好的語句執行的，我會獲得占位符（$ 1）而不是正確的值。 例如（已記錄的查詢）：

delete from some_table where id=$1

有沒有辦法獲得/擁有這個值/參數？

已編輯（已添加示例）：

--table for saving query
create table log_table (
query text
)

--table for trigger
create table some_table (
id text
)
--function itself
CREATE FUNCTION save_query() RETURNS trigger AS $$
    switch $TG_op {
    DELETE {
            spi_exec "INSERT INTO log_table (query) VALUES (current_query())"
        }
    default {
            return OK
        }
    }
    return OK
$$ LANGUAGE pltcl;

創建一個觸發器：

create trigger test_trigger before delete on some_table for each row execute procedure save_query();

准備好的語句是從hibernate執行的。

再次編輯（添加了java部分）

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

public class DeleteUsingPreparedStmt {

    public static void main(String[] args) {
        try {
            String deleteString = "delete from floors where id = ? ";
            final int idToDelte = 1;

            Class.forName("org.postgresql.Driver");
            String url = "jdbc:postgresql://127.0.0.1:5432/YOUR_DATABASE";
            Connection conn = DriverManager.getConnection(url, "user", "password");

            PreparedStatement deleteStmt = conn.prepareStatement(deleteString);
            deleteStmt.setInt(1, idToDelte);
            deleteStmt.executeUpdate();
        } catch (Exception e) {
            //hide me :)
        }
    }
}

你需要一個jdbc驅動程序 - 點擊 。

Answer 1

這是一些工作代碼（對於Debian用戶：只需安裝postgresql-pltcl-8.4包並運行CREATE LANGUAGE pltcl; ）

CREATE TABLE log_table (
    id serial,
    query text
);

CREATE TABLE floors (
    id serial,
    value text
);

INSERT INTO floors(value) VALUES ('aaa'), ('bbb');

CREATE OR REPLACE FUNCTION save_query() RETURNS trigger AS $$
    switch $TG_op {
        DELETE {
            spi_exec "INSERT INTO log_table (query) VALUES (current_query())"
        }
        default {
            return OK
        }
    }
    return OK
$$ LANGUAGE pltcl;

CREATE TRIGGER test_trigger
    BEFORE DELETE ON floors
    FOR EACH ROW
    EXECUTE PROCEDURE save_query();

但是我無法在EXECUTE deleteFromFloors(2);准備語句中獲取占位符（它返回EXECUTE deleteFromFloors(2); ）：

TABLE log_table;
 id | query 
----+-------
(0 rows)
DELETE FROM floors WHERE id = 1;
DELETE 1
TABLE log_table;
 id |              query               
----+----------------------------------
  1 | DELETE FROM floors WHERE id = 1;
(1 row)
PREPARE deleteFromFloors(integer) AS
    DELETE FROM floors WHERE id = $1;
PREPARE
EXECUTE deleteFromFloors(2);
DELETE 1
TABLE log_table;
 id |              query               
----+----------------------------------
  1 | DELETE FROM floors WHERE id = 1;
  2 | EXECUTE deleteFromFloors(2);
(2 rows)

編輯：

作為一種解決方法，使用OLD記錄（在Tcl中表示為數組），從那里獲取id列並使用replace函數來代替$1 。 這里有兩個解決方案：PL / pgSQL和PL / Tcl：

CREATE OR REPLACE FUNCTION save_query() RETURNS TRIGGER AS $$
BEGIN
    INSERT INTO log_table (query)
        VALUES (replace(current_query(), '$1', OLD.id::text));
    RETURN OLD;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION save_query() RETURNS trigger AS $$
    switch $TG_op {
        DELETE {
            spi_exec "INSERT INTO log_table (query)
                VALUES (replace(current_query(), '\$1', '$OLD(id)'))"
        }
        default {
            return OK
        }
    }
    return OK
$$ LANGUAGE pltcl;

結果：

java -classpath '.:postgresql-8.4-702.jdbc4.jar' DeleteUsingPreparedStmt

TABLE log_table;
 id |              query              
----+---------------------------------
  1 | delete from floors where id = 1

（1排）