On 01/15/2013 11:31 AM, Andrew Dunstan wrote:
> On 01/14/2013 11:02 PM, Andrew Dunstan wrote:
>> On 01/14/2013 12:52 PM, Andrew Dunstan wrote:
>>> On 01/14/2013 11:32 AM, Robert Haas wrote:
>>>> So, how much performance does this lose on json_in() on a large
>>>> cstring, as compared with master?
>>> That's a good question. I'll try to devise a test.
>>>> I can't shake the feeling that this is adding a LOT of unnecessary
>>>> data copying. For one thing, instead of copying every single lexeme
>>>> (including the single-character ones?) out of the original object, we
>>>> could just store a pointer to the offset where the object starts and a
>>>> length, instead of copying it.
>>> In the pure pares case (json_in, json_reccv) nothing extra should be
>>> copied. On checking this after reading the above I found that wasn't
>>> quite the case, and some lexemes (scalars and field names, but not
>>> punctuation) were being copied when not needed. I have made a fix
>>> which I will include in the next version I publish.
>>> In the case of string lexemes, we are passing back a de-escaped
>>> version, so just handing back pointers to the beginning and end in
>>> the input string doesn't work.
>> After a couple of iterations, some performance enhancements to the
>> json parser and lexer have ended up with a net performance
>> improvement over git tip. On our test rig, the json parse test runs
>> at just over 13s per 10000 parses on git tip and approx 12.55s per
>> 10000 parses with the attached patch.
>> Truth be told, I think the lexer changes have more than paid for the
>> small cost of the switch to an RD parser. But since the result is a
>> net performance win PLUS some enhanced functionality, I think we
>> should be all good.
> Latest version of this patch, including some documentation, mainly
> from Merlin Moncure but tweaked by me.
Now with more comments.
In response to
pgsql-hackers by date
|Next:||From: Tom Lane||Date: 2013-01-15 22:46:57|
|Subject: Re: [PATCH] COPY .. COMPRESSED|
|Previous:||From: Bruce Momjian||Date: 2013-01-15 22:45:15|
|Subject: Re: Parallel query execution|