Re: Pluggable storage

From: Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
To: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Pluggable storage
Date: 2017-07-14 13:35:56
Views: Raw Message | Whole Thread | Download mbox
Lists: pgsql-hackers

On Wed, Jun 28, 2017 at 1:16 PM, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
> Accepting multiple tuple format is possible with complete replacement of
> HeapTuple with TupleTableSlot or something like value/null array
> instead of a single memory chunk tuple data.
> Currently I am working on it to replace the HeapTuple with TupleTableSlot
> in the upper layers once the tuples is returned from the scan. In most of
> the
> places where the HeapTuple is present, either replace it with
> TupleTableSlot
> or change it to StorageTuple (void *).
> I am yet to evaluate whether it is possible to support as an independent
> feature
> without the need of some heap format function to understand the tuple
> format
> in every place.

To replace tuple with slot, I took trigger and SPI calls as the first step
in modifying
from tuple to slot, Here I attached a WIP patch. The notable changes are,

1. Replace most of the HeapTuple with Slot in SPI interface functions.
2. In SPITupleTable, Instead of HeapTuple, it is changed to TupleTableSlot.
But this change may not be a proper approach, because a duplicate copy of
TupleTableSlot is generated and stored.
3. Changed all trigger interfaces to accept TupleTableSlot Instead of
4. ItemPointerData is added as a member to the TupleTableSlot structure.
5. Modified the ExecInsert and others to work directly on TupleTableSlot
of tuple(not completely).

In many places while accessing system tables, the tuple is directly mapped
a catalog table structure and accessed. Currently I am not modifying any of
and leaving them as it is until we solve all other HeapTuple replacement

In order to continue further changes in replacing the HeapTuple with
I am just thinking of replacing Trigger functions like plpgsql_exec_trigger
to return
TupleTableSlot instead of HeapTuple. I am thinking that these changes may
the performance as it avoids the deform and forming a tuple. I am thinking
same TupleTableSlot memory is valid across these function calls. Am I

I am thinking that it may not possible to replace all the places of
HeapTuple with
TupleTableSlot, but it is possible with a StorageTuple (which is a void*).
the tuple is present, there exists a tupledesc in most of the cases. How
adding some kind of information in tupledesc to find out the tuple format
and call
the necessary functions to generate a TupleTableSlot from it and use that
from there
onward? This approach may be useful for Storing StorageTuple in
instead of TupleTableSlot.

Please let me know your comments/suggestions.

Hari Babu
Fujitsu Australia

Attachment Content-Type Size
0001-WIP-tuple-replace-with-slot.patch application/octet-stream 152.0 KB

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Alik Khilazhev 2017-07-14 13:37:50 Re: [WIP] Zipfian distribution in pgbench
Previous Message Heikki Linnakangas 2017-07-14 13:07:46 Re: BUG #14634: On Windows pg_basebackup should write tar to stdout in binary mode