在 Postgres 中为特定查询设置 work_mem [英] Setting work_mem in Postgres for specific queries
问题描述
我使用的库委托给 PostgreSQL
的 JDBC 驱动程序,有些查询非常复杂,需要更多内存.我不想将 work_mem
设置为所有查询的大值,只是这个子集.问题是执行以下代码会导致错误:
I'm using a library that delegates to a JDBC driver for PostgreSQL
, and some queries are very complex and require more memory. I don't want to set work_mem
to something large for all queries, just this subset. The problem is that executing the following code results in an error:
// pseudo-code for what is happening
String sql = "set work_mem = 102400;";
sql += "SELECT * FROM expensive_query";
ResultSet rs = DatabaseDriver.execute(sql);
当我运行这个时,我得到一个错误:
When I run this I get an error that:
set work_mem = 102400;
不返回任何结果.
这在 pgAdmin
中有效,因为您可以一次执行多个查询.有没有更好的方法来做到这一点,还是我需要执行任意 SQL 然后提取我想要的结果集?
This works in pgAdmin
because you can execute multiple queries at once. Is there a better way to do this or do I need to execute arbitrary SQL and then extract the result set I want?
推荐答案
我不知道 DatabaseDriver
是做什么的,但是使用普通"JDBC,您只需要执行以下操作:
I have no idea what DatabaseDriver
does, but with "plain" JDBC you just need to do the following:
Statment stmt = connection.createStatement();
stmt.execute("set work_mem = 102400");
ResultSet rs = stmt.executeQuery("select ...");
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