Re: Actual Cost

From: Donald Dong <xdong(at)csumb(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: David Fetter <david(at)fetter(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Actual Cost
Date: 2019-02-18 02:27:13
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On Feb 17, 2019, at 11:05 AM, Donald Dong <xdong(at)csumb(dot)edu> wrote:
> On Feb 17, 2019, at 10:56 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Perhaps, but refactoring to get that seems impractically invasive &
>> expensive, since e.g. index AM cost estimate functions would have to
>> be redefined, plus we'd have to carry around some kind of cost vector
>> rather than single numbers for every Path ...
> Maybe we could walk through the final plan tree and fill the expression? With another tree structure to hold the cost vectors.

Here is a draft patch. I added a new structure called CostInfo to the Plan node. The CostInfo is be added in create_plan, and the cost calculation is centered at CostInfo. Is this a reasonable approach?

Thank you,
Donald Dong

Attachment Content-Type Size
01_actual_cost_seqscan_001.patch application/octet-stream 8.3 KB

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