Re: jsonb access operators inefficiency

On 05/30/2014 09:35 AM, Teodor Sigaev wrote:
> Hi!
>
> jsonb operators ->text, ->>text,->int, ->>int use inefficient methods 
> to access to needed field, proportional O(N/2). Attached patch 
> suggests for text operators O(log(N)) and for integer - O(1). The 
> fuctions with fast access already are existed in current code and are 
> used in contains operation, for example. Attached patch uses that 
> functions instead of sequentual loop over object/array.

Teodor, thanks for this.

My only worry is this sort of code, which in a quick search I didn't 
find used elsewhere
   -                   (void) JsonbToCString(jtext, &tjb->root , -1);   -                   result =
cstring_to_text_with_len(jtext->data,  jtext->len);   +                   appendStringInfoSpaces(jtext, VARHDRSZ);   +
                (void) JsonbToCString(jtext, v->val.binary.data,   -1);   +   +                   result =
(text*)jtext->data;  +                   SET_VARSIZE(result, jtext->len);
 


If we're going to construct varlena objects inside a StringInfo, maybe 
we need a proper API for it. Isn't there a danger that data member of 
the StringInfo won't be properly aligned to allow us to do this? In any 
case, we should get most of the benefit of your patch without this 
"optimization".

cheers

andrew