Re: cached plan must not change result type

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

James Pang <jamespang886(at)gmail(dot)com> 於 2024年3月29日週五 下午4:56寫道：

> Thanks Laurenz, 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
> .
>
>
>
> Thanks,
>
>
>
> James
>
> Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> 於 2024年3月29日週五 下午4:40寫道：
>
>> On Fri, 2024-03-29 at 10:05 +0800, James Pang wrote:
>> > PGV14, client use PGJDBC driver and prepared statements, when a table
>> > "alter table alter column type ..." changes done, a lot of JDBC clients
>> > got this error "cached plan must not change result type". when a JDBC
>> > client got this error first time after the DDL schema change, JDBC
>> driver
>> > will clear this caching-plan and following same SQL statement got
>> parsing
>> > again and new cached plan right?
>>
>> Not sure; what do you observe?
>> Anyway, this is a known problem:
>> https://jdbc.postgresql.org/documentation/server-prepare/#ddl
>>
>> > How to avoid this issue when DDL schema changes ?
>>
>> Don't use server-side prepared statements:
>> https://jdbc.postgresql.org/documentation/server-prepare/#deactivation
>> You'll lose some performance though.
>>
>> Questions like this had better be asked on the pgsql-jdbc list.
>>
>> Yours,
>> Laurenz Albe
>>
>