Message-ID: <24AD6A221A5B4B03B87163A772D2F8BB@squarepi.com>
From: "John Lister" <john.lister-ps@kickstone.com>
To: "Andrew Chernow" <ac@esilo.com>
Cc: <pgsql-hackers@postgresql.org>
References: <89DBB5874E89413698A8E275E5E79154@squarepi.com>
	<4ECCF5BAADF94C5E9FD5CF2FA52CD061@squarepi.com>
	<49DCBB2F.7040406@esilo.com> <49DCBDBB.9070303@esilo.com>
Subject: Re: Array types
Date: Wed, 8 Apr 2009 16:11:55 +0100
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Cheers for the pointers. Am i right in thinking that if i get an array of 
arrays, the nested arrays are sent in wire format as well - it seems to be 
from the docs.

Secondly, comments are a bit scarse in the code, but am i also right in 
thinking that an array indexing can start at an arbitrary value? This seems 
to be what the lbound value is for... or is this a addition to deal with 
nulls eg, {null, null, null, 4} would have a lbound of 3.... (or both)

Thanks

----- Original Message ----- 
From: "Andrew Chernow" <ac@esilo.com>
To: "John Lister" <john.lister-ps@kickstone.com>
Cc: <pgsql-hackers@postgresql.org>
Sent: Wednesday, April 08, 2009 4:07 PM
Subject: Re: [HACKERS] Array types


> Andrew Chernow wrote:
>> John Lister wrote:
>>> Following this up, is there any docs on the binary wire format for 
>>> arrays?
>>>
>>
>> None that I know of.
>>
>> Check out the backend source: (array_recv() and array_send() functions)
>> http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/arrayfuncs.c?rev=1.154 
>> Or, look at libpqtypes array.c:
>> http://libpqtypes.esilo.com/browse_source.html?file=array.c
>>
>
> Forgot to mention, this is not as simple as understanding the array 
> format.  You have to understand the wire format for all types that can be 
> array elements.  The array wire format serializes its array elements as 
> [elem_len][elem_data].  elem_data is the wire format of the array element 
> type, like an int, timestamp, polygon, bytea, etc...  So once you unravel 
> the array container format, you still have to demarshal the type data.
>
> -- 
> Andrew Chernow
> eSilo, LLC
> every bit counts
> http://www.esilo.com/
>