8次尝试后，执行Postgres SQL Select语句的速度降低了10倍

Question

我们有一个15000000条目数据库，并执行

之类的SELECT。

SELECT technical_id, attribute_a, attribute_b, attribute_c from test WHERE ( attribute_a_fltr @> (?::character varying[]) OR attribute_a_fltr = '{n/a}') AND ( attribute_b_fltr @> (?::character varying[]) OR attribute_b_fltr = '{n/a}') AND ( attribute_c = ? OR attribute_c = 0)

将在尝试9次后急剧降低。这是结果

Iteration: 0 Entries: 593 time :6931
Iteration: 1 Entries: 593 time :7879
Iteration: 2 Entries: 593 time :8721
Iteration: 3 Entries: 593 time :9490
Iteration: 4 Entries: 593 time :10240
Iteration: 5 Entries: 593 time :11016
Iteration: 6 Entries: 593 time :11736
Iteration: 7 Entries: 593 time :12461
Iteration: 8 Entries: 593 time :13168
Iteration: 9 Entries: 593 time :152329
Iteration: 10 Entries: 593 time :290717
Iteration: 11 Entries: 593 time :435933
Iteration: 12 Entries: 593 time :567401
Iteration: 13 Entries: 593 time :695307
Iteration: 14 Entries: 593 time :835853

这是Java代码

            Connection connection = DriverManager.getConnection("jdbc:postgresql://localhost:5432/test-db", props);
        PreparedStatement prepStatement = connection.prepareStatement(FILTER_7);
        prepStatement.setString(1,"{AAAAAAIAAAAAIAAAAAAAAgAAAAAgAAAAAAACAAAAACAAAAAAAAIAAgAAIAAgAAAAAgACAAAgACAAAAAAAAIA}");
        prepStatement.setString(2,"{gAAAAAAQAAAAAAIAAABAAAAAAAgAAAAAAQAAACAAAAAABAAAAIAAAAAAEAAAAAACAAAAQAAAAgAIAEAAAAAA}");
        prepStatement.setInt(3, 1979);
        long t0 = System.currentTimeMillis();
        long iter = 0;
        while (true) {
            ResultSet resultSet = prepStatement.executeQuery();
            long count = 0;
            while(resultSet.next()) {
                ++count;
            }
            System.out.println("Iteration: "+iter +" Entries: "+ count + " time :" + (System.currentTimeMillis() - t0));
            ++iter;
        }