Re: patch: streaming of bytea parameter values

Kris Jurka wrote:
>
> On Wed, 21 Apr 2004, Oliver Jowett wrote:
>
>
>>This patch allows bytea parameters set via setBytes() /
>>setBinaryStream() to be streamed to the backend. With the patch applied,
>>the additional memory overhead for bytea parameters is small and
>>independent of how large the parameter data is.
>
>
> Have you given any consideration to extending this to handle streaming
> large text fields via setAsciiStream(), setUnicodeStream(), or
> setObject(int, Object, Types.LONGVARCHAR) ? Also updateable ResultSets
> have similar updateXXX to PreparedStatement's setXXX methods that could
> benefit from a streaming interface.

I think setObject() should use the changes when given a byte[], as it
appears to delegate to setBytes() in that case.. although I find the
setObject logic hard to follow at times (you are in a maze of twisty
little case statements, all alike)

updateBytes() delegates to setObject(). updateBinaryStream() won't
stream, at a glance, but should be easy to change so it delegates to
setBinaryStream().

From a quick look at the other streaming parameter types, it's not
clear that we can stream them. setUnicodeStream and setCharacterStream
can't be streamed under v3 as there's no simple relationship between the
length parameter provided and the number of UTF8-encoded bytes we'd send
to the backend. setAsciiStream could be streamed if we assume 7-bit
ASCII (1:1 mapping to UTF8) but the JDBC javadoc doesn't say exactly
what it means by "ASCII"..

> There is also the implied assumption that V3 protocol implies a unicode
> client encoding which implies a seven bit safe streaming option which
> would be better spelled out in a comment or called in a way that used the
> encoding variable to derive this fact.

Fair comment.

In my local tree, this patch has been superceded by changes to use the
v3 extended query protocol and stream the data directly as a binary
parameter. I thought it might make a good interim solution for the
official driver though.

-O