Re: cached plan must not change result type - Mailing list pgsql-jdbc

From Dave Cramer
Subject Re: cached plan must not change result type
Date
Msg-id CADK3HHLkuDpfVKfzckH5z-e1_Z8DH-9WdOWaafbJ4HRuRqnsdg@mail.gmail.com
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In response to Re: cached plan must not change result type  (James Pang <jamespang886@gmail.com>)
Responses Re: cached plan must not change result type
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On Fri, 29 Mar 2024 at 05:09, James Pang <jamespang886@gmail.com> wrote:

 forwarded to pgjdbc,  we want to understand why JDBC failed to reexecute the SQL instead of throw error out. Like this document https://jdbc.postgresql.org/documentation/server-prepare/#re-execution-of-failed-statements .

 


protected final void execute(CachedQuery cachedQuery,
      @Nullable ParameterList queryParameters, int flags)
      throws SQLException {
    try {
      executeInternal(cachedQuery, queryParameters, flags);
    } catch (SQLException e) {
      // Don't retry composite queries as it might get partially executed
      if (cachedQuery.query.getSubqueries() != null                                 <<< no idea how this  cachedQuery.query.getSubqueries() != null
          || !connection.getQueryExecutor().willHealOnRetry(e)) {
        throw e;
      }
      cachedQuery.query.close();
      // Execute the query one more time
      executeInternal(cachedQuery, queryParameters, flags);
    }
  }

cachedQuery.query.getSubqueries() != null, how this code decide composite queries  here ?   that mean some query having subquery or having many JOIN or LEFT JOINs like  select .... A left join B ...

Thanks,

James 

This is really an issue that needs to be solved in the backend. The error is coming from PostgreSQL and what should happen is that when you alter a table that a server prepared statement relies on the backend should send a message to tell us that all of the prepared statements that rely on are now invalid and we can reprepare them. Currently the driver has no idea that you changed the table and the prepared statement will fail so it just continues to use it.

Dave

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