Question

我有以下postgresql功能：

CREATE OR REPLACE FUNCTION readMessage(messageFor INT, qid INT = NULL, ctxt INT = NULL, messageFrom INT = NULL, byTimeStamp BOOLEAN = FALSE)
RETURNS SETOF message
AS $$
DECLARE
    sql varchar;
BEGIN
    sql := 'SELECT * FROM message WHERE (receiver_id IS NULL OR receiver_id = $1)';
    IF qid IS NOT NULL THEN
        sql := sql || ' AND queue_id = $2';
    END IF;
    IF ctxt IS NOT NULL THEN
        sql := sql || ' AND context = $3';
    ELSE
        sql := sql || ' AND context IS NULL';
    END IF;

    IF $4 IS NOT NULL THEN
        sql := sql || ' AND sender_id = $4';
    END IF;

    sql := sql || ' ORDER BY';
    IF byTimeStamp THEN
        sql := sql || ' arrive_time ASC';
    ELSE
        sql := sql || ' priority DESC';
    END IF;

    sql := sql || ' LIMIT 1'; 
    RETURN QUERY EXECUTE sql
    USING messageFor, qid, ctxt, messageFrom;
END;
$$
LANGUAGE plpgsql;

现在，上面的函数工作正常，但resultSet不包含列名（例如：一个简单的SELECT语句返回带有列名的结果）。我需要能够在Java代码中访问上述函数的结果为：

Connection con;
PreparedStatement ps = con.prepareStatement("select readMessage(1, 1, 1, 1, true))";
ResultSet rs = ps.executeQuery(); 
rs.getInt(<column-name>) // for example: 'queue_id', 'context' etc.

而不是

rs.getInt(<column-index>)

用于更易读的代码。如何修改postgresql FUNCTION来实现这个目标？

Answer 1

嗯，我想要实现的目标有一个非常简单的解决方案（虽然它不会修改FUNCTION）。在Java中，只需调用

PreparedStatement ps = con.prepareStatement("select * from readMessage(1, 1, 1, 1, true))";

而不是

PreparedStatement ps = con.prepareStatement("select readMessage(1, 1, 1, 1, true))";

从postgresql存储过程返回带有列名的ResultSet

1 个答案: