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 (see <https://bitbucket.org/adunstan/pgdevel/commits/139043dba7e6b15f1f9f7675732bd9dae1fb6497>) 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.
This is also remarkably thin on comments.
Fair criticism. I'll work on that. Thanks for looking at this. cheers andrew -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
