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From: SuperPat45 (@SuperPat45) <[email protected]>
To: pgjdbc/pgjdbc <[email protected]>
Subject: [pgjdbc/pgjdbc] issue #2861: setFetchSize is ignored?
Date: Tue, 21 Mar 2023 15:48:48 +0000
Message-ID: <[email protected]> (raw)

Please read https://stackoverflow.com/help/minimal-reproducible-example 

**Describe the issue**
Due to a bug, I have a query that returned 1 million rows instead of 10000....
I specified that I wanted the database to return only 100 rows at a time.

I noticed that the memory was full before the executeQuery() function returned the ResultSet...
Looking with JVisualVM I saw hundreds of thousands instances of the org.postgresql.core.Tuple class
So, It seem that all rows are fetched ignoring the fetchSize limit.

**Driver Version?** 
42.5.0

**Java Version?**
17.0.4

**OS Version?**
Windows 10

**PostgreSQL Version?**
14.5

**To Reproduce**
```
Statement statement = connection.createStatement();
statement.setFetchSize(100);
ResultSet resultSet = statement.executeQuery("select * from one_million_row_table");
System.out.println("OK");
```

**Expected behaviour**
The result set should have been returned by the executeQuery() function without exploding the memory as I specified to only fetch 100 rows at a time.
I use the result set to write data in a text file so, in this case, the memory should never have been filled completely.

**Logs**
java.lang.OutOfMemoryError: Java heap space

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