java - PostgreSQL- getColumnName 不工作，返回别名

Question

我正在尝试从下面的查询中获取列名，

SELECT
    category as c1,
    forecast_2016,
    category,
    rowcount,
    item_number,
    rowcount,
    category,
    avg_demand_2014_2015,
    category,
    avg_spend_2014_2015,
    avg_demand_2014_2015,
    avg_spend_2014_2015,
    demand_2015
FROM
    ag_instrument_portfolio_master LIMIT 1

Postgres版本为9.3，Java版本为1.7，java实现如下。

stmt = con.createStatement();
rs = stmt.executeQuery(query.toString());
ResultSetMetaData columnsMetadata = rs.getMetaData();
int i = 0;
while (i < columnsMetadata.getColumnCount()) {
    i++;
    System.out.println("Name: " + columnsMetadata.getColumnName(i));
    System.out.println("Label: " + columnsMetadata.getColumnLabel(i));
}

输出是

Name: c1
Label: c1

但是，预期是

Name: category
Label: c1

Answer 1

鉴于 pgsql-jdbc 邮件列表中的评论 here ，看来您看到的是 PostgreSQL JDBC 驱动程序的“设计”行为:

This is a limitation of the information the driver gets back from the server, it only returns the 'label' which the driver then uses for both columnname and label.

与 JDBC 的许多其他方面一样，给定功能的行为通常会因特定 JDBC 驱动程序的实现而异。