Re: Declarative partitioning

Hi,

On 2016/03/09 9:17, Corey Huinker wrote:
>>
>> Sorry for replying so late.
> No worries! We have jobs to do aside from this.

Thanks!

>> Everything seemed to go dandy until I tried FOR VALUES (blah , blah],
>> where psql wouldn't send the command string without accepting the closing
>> parenthesis, :(. So maybe I should try to put the whole thing in '', that
>> is, accept the full range_spec in a string, but then we are back to
>> requiring full-blown range parse function which I was trying to avoid by
>> using the aforementioned grammar. So, I decided to move ahead with the
>> following grammar for time being:
>>
>> START (lower-bound) [ EXCLUSIVE ]
>> | END (upper-bound) [ INCLUSIVE ]
>> | START (lower-bound) [ EXCLUSIVE ] END (upper-bound) [ INCLUSIVE ]
>>
>> Where,
>>
>> *-bound: a_expr
>> | *-bound ',' a_expr
>>
>> Note that in the absence of explicit specification, lower-bound is
>> inclusive and upper-bound is exclusive.
>
> Thanks for trying. I agree that it would be a full blown range parser, and
> I'm not yet advanced enough to help you with that.
>
> So presently partitions that are unbounded on the lower end aren't
> possible, but that's a creation syntax issue, not an infrastructure issue.
> Correct?

In case it wasn't apparent, you can create those:

FOR VALUES END (upper-bound) [INCLUSIVE]

which is equivalent to:

FOR VALUES '(, upper-bound)' or FOR VALUES '(, upper-bound]'

>>> Question: I haven't dove into the code, but I was curious about your
>> tuple
>>> routing algorithm. Is there any way for the algorithm to begin it's scan
>> of
>>> candidate partitions based on the destination of the last row inserted
>> this
>>> statement? I ask because most use cases (that I am aware of) have data
>> that
>>> would naturally cluster in the same partition.
>>
>> No. Actually the tuple-routing function starts afresh for each row. For
>> range partitions, it's binary search over an array of upper bounds. There
>> is no row-to-row state caching in the partition module itself.
>>
>>
> bsearch should be fine, that's what I've used in my own custom partitioning
> schemes.
>
> Was there a new patch, and if so, is it the one you want me to kick the
> tires on?

You didn't miss any. I need a little more time to send the next revision
with significant design overhaul.

Thanks,
Amit