Re: Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options

Thanks for updating the patch.

>> It seems you allow to use IGNORE NULLS for all window functions. If
>> the case, you should explicitely stat that in the docs. Otherwise
>> users will be confused because;
> 
> The latest version restricts it to lag, lead, first_value, last_value,
> and nth_value. We can extend it in a subsequent patch if there's
> demand?

The restriction is required by the SQL standard. So I don't think we
need to extend to other window functions.

>> I take a look at the patch and noticed that following functions have
>> no comments on what they are doing and what are the arguments. Please
>> look into other functions in nodeWindowAgg.c and add appropriate
>> comments to those functions.
> 
> Latest version has more comments and should be in the standard coding style.

Still I see non standard coding stiles and indentations. See attached
patch for nodeWindowAgg.c, which is fixed by pgindent, for
example. (Other files may need fixing too).

>> I also notice that you have an array in memory which records non-null
>> row positions in a partition. The position is represented in int64,
>> which means 1 entry consumes 8 bytes. If my understanding is correct,
>> the array continues to grow up to the partition size. Also the array
>> is created for each window function (is it really necessary?). I worry
>> about this because it might consume excessive memory for big
>> partitions.
> 
> It's an int64 because it stores the abs_pos/mark_pos which are int64.
> Keeping an array for each function is needed for the mark optimization
> to work correctly.

Ok.

Here are some comments regarding the patch:

(1) I noticed that ignorenulls_getfuncarginframe() does not take
account EXCLUSION frame options. The code path is in
WinGetFuncArgInFrame():

			/*
			 * Account for exclusion option if one is active, but advance only
			 * abs_pos not mark_pos.  This prevents changes of the current
			 * row's peer group from resulting in trying to fetch a row before
			 * some previous mark position.
:
:

I guess ignorenulls_getfuncarginframe() was created by modifying
WinGetFuncArgInFrame() so I don't see the reason why
ignorenulls_getfuncarginframe() does not take account EXCLUSION frame
options.

(2) New member ignore_nulls are added to some structs. Its value is 0,
1 or -1. It's better to use a DEFINE for the value of ignore_nulls,
rather than 0, 1, or -1.

Best reagards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp