PostgreSQLComExecuteExecutor may cause OOM when packet.getMaxRows() = 0

`PostgreSQLComExecuteExecutor` has a potential Out-Of-Memory (OOM) problem.

When packet.getMaxRows() is 0, and the returned result set is extremely large, the executor will attempt to write all result packets into memory. This behavior can easily lead to an OOM error under high-volume queries.

Start by locating PostgreSQLComExecuteExecutor and tracing how packet.getMaxRows() controls result-packet buffering. Check the surrounding executor code and its existing tests, if present. Done means a very large result set with maxRows equal to 0 no longer accumulates all result packets in memory or causes an OOM.

Written by the indexing model from the issue text.