Date: Fri, 18 Dec 2020 11:54:39 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Andres Freund <andres@anarazel.de>, Luc Vlaming <luc@swarm64.com>,
	Paul Guo <guopa@vmware.com>
Subject: Re: New Table Access Methods for Multi and Single Inserts
Message-ID: <20201218175439.GA30237@telsasoft.com>
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On Fri, Dec 18, 2020 at 07:39:14AM +0530, Bharath Rupireddy wrote:
> On Fri, Dec 18, 2020 at 2:14 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> > Are you thinking that TableInsertState would eventually have additional
> > attributes which would apply to other tableams, but not to heap ?  Is
> > heap_insert_begin() really specific to heap ?  It's allocating and populating a
> > structure based on its arguments, but those same arguments would be passed to
> > every other AM's insert_begin routine, too.  Do you need a more flexible data
> > structure, something that would also accomodate extensions?  I'm thinking of
> > reloptions as a loose analogy.
> 
> I could not think of other tableam attributes now. But +1 to have that
> kind of flexible structure for TableInsertState. So, it can have
> tableam type and attributes within the union for each type.

Right now you have heap_insert_begin(), and I asked if it was really
heap-specific.  Right now, it populates a struct based on a static list of
arguments, which are what heap uses.  

If you were to implement a burp_insert_begin(), how would it differ from
heap's?  With the current API, they'd (have to) be the same, which means either
that it should apply to all AMs (or have a "default" implementation that can be
overridden by an AM), or that this API assumes that other AMs will want to do
exactly what heap does, and fails to allow other AMs to implement optimizations
for bulk inserts as claimed.

I don't think using a "union" solves the problem, since it can only accommodate
core AMs, and not extensions, so I suggested something like reloptions, which
have a "namespace" prefix (and core has toast.*, like ALTER TABLE t SET
toast.autovacuum_enabled).

-- 
Justin