Thread: Patch: Force Primitives

On 03/25/2013 05:51 PM, Nicholas White wrote:
> I've revised the patch to make Array.getArray() return a primitive array even when using the binary transfer format.
Ihad to add extra code to force a 
> statement to do a describe query before executing (previously it would only do this if the org.postgresql.forcebinary
systemproperty was set), as the 
> QueryExecutorImpl needs the Field objects to be populated when sendBind is called, or the query results will be sent
backin Text format. The PrimitivesTest 
> unit test my patch adds verifies that a column is being returned in the correct (text or binary) format. I think this
fixesan outstanding bug; I believe binary 
> transfers will only be used if the system property is set, and the binaryTransfer JDBCUrl parameter is currently
useless.

By default the binary transfers for receive kick in only after the 3rd execution of a prepared statement. Do you see
thebinary transfers activating for array  
receives if you run your prepared statement select in a loop?

The forceBinary option is for unit tests that do not want to repeat every statement 3 times.

-Mikko

On 03/25/2013 08:24 PM, Nicholas White wrote:
>  > Do you see the binary transfers activating for array receives if you run your prepared statement select in a loop?
> That's the behaviour I see, athough something's setting my m_prepareThreshold to 5 rather than 3. I'm essentially
usingpostgres as a persistent cache for my 
> application server; when my app server starts it loads large amounts of data from postgres using a series of
select-*-from-xqueries. In order to minimise 
> network I/O I'd ideally like a way to ensure I'm using the binary protocol from the very first query. Should I submit
anotherpatch that lets you configure this 
> behaviour (either via a new JDBCUrl parameter or whether binaryTransfer is explicitly specified)?

I can't remember how the prepareTheshold goes. Is it so that even setting it to 1 (0 disables them) you still get real
preparedstatements (and at the same 
time binary transfers) on the second execution. If you have an application that benefits from binary transfers on the
firstexecution then yes, we should add 
an option to enable that behaviour. So another patch for that would be nice.

> Separately, do you know why this behaviour is the default? Is the binary encoding more expensive (either server-side
orclient-side) than text encoding the data? 

It's not because of binary encoding, which is faster on both server and client side.

The current functionality tries to avoid the extra describe overhead (is it even a roundtrip?) for prepared statements
thatare only executed once (or very few  
times), which is quite common in many applications that seem to use prepared statements also for one-shot cases.

PS. if you are concerned about binary array transfer performance I did some work last year to optimize the protocol for
arraysthat do not contain nulls.  
Unfortunately there was never any resolution to the server side patches. The discussion got stuck on weather updates
withfeature flags, adding a minor version  
number to the protocol or just wait for pg 10 to break the protocol is the correct way to go forward.

You can grab the server side + jdbc patches from here:
http://www.postgresql.org/message-id/4ECC186A.30709@nitorcreations.com

-Mikko