Re: pgbench more operators & functions

From: David Steele <david(at)pgmasters(dot)net>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Jeevan Ladhe <jeevan(dot)ladhe(at)enterprisedb(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pgbench more operators & functions
Date: 2017-03-16 16:21:31
Message-ID: b122f198-7c1b-d268-ac56-9a2400cf1eb5@pgmasters.net
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On 2/4/17 4:51 AM, Fabien COELHO wrote:
>
> Hello,
>
>> For my 2c, at least, while I'm definitely interested in this, it's not
>> nearly high enough on my plate with everything else going on to get any
>> attention in the next few weeks, at least.
>>
>> I do think that, perhaps, this patch may deserve a bit of a break, to
>> allow people to come back to it with a fresh perspective, so perhaps
>> moving it to the next commitfest would be a good idea, in a Needs Review
>> state.
>
> So, let's try again for the next CF...
>
> Here is a v9 which includes some more cleanup, hopefully in the expected
> direction which is to make pgbench expressions behave as SQL
> expressions, and I hope taking into account all other feedback as well.
>
>
> CONTEXT
>
> Pgbench has been given an expression parser (878fdcb8) which allows to
> use full expressions instead of doing one-at-a-time operations. This
> parser has been extended with functions (7e137f84) & double type
> (86c43f4e). The first batch of functions was essentially a poc about how
> to add new functions with various requirements. Pgbench default
> "tpcb-like" test takes advantage of these additions to reduce the number
> of lines it needs.
>
>
> MOTIVATION
>
> This patch aims at providing actually useful functions for benchmarking.
> The functions and operators provided here are usual basic operations.
> They are not chosen randomly, but are simply taken from existing
> benchmarks:
>
> In TPC-B 2.0.0 section 5.3.5 and TPC-C 5.11 section 2.5.1.2, the
> selection of accounts uses a test (if ...), logical conditions (AND, OR)
> and comparisons (<, =, >=, >).
>
> In TPC-C 5.11 section 2.1.6, a bitwise or (|) is used to skew a
> distribution based on two uniform distributions.
>
> In TPC-C 5.11 section 5.2.5.4, a log function is used to determine
> "think time", which can be truncated (i.e. "least" function, already in
> pgbench).
>
>
> CONTENTS
>
> The attached patch provides a consistent set of functions and operators
> based on the above examples, with operator precedence taken from
> postgres SQL parser:
>
> - "boolean" type support is added, because it has been requested that
> pgbench should be as close as SQL expressions as possible. This induced
> some renaming as some functions & struct fields where named "num"
> because they where expecting an int or a double, but a boolean is not
> really a numeral.
>
> - SQL comparisons (= <> < > <= >=) plus pg SQL "!=", which result in a
> boolean.
>
> - SQL logical operators (and or not) on booleans.
>
> - SQL bitwise operators taken from pg: | & # << >> ~.
>
> - mod SQL function as a synonymous for %.
>
> - ln and exp SQL functions.
>
> - SQL CASE/END conditional structure.
>
> The patch also includes documentation and additional tap tests.
> A test script is also provided.
>
> This version is strict about typing, mimicking postgres behavior. For
> instance, using an int as a boolean results in a error. It is easy to
> make it more tolerant to types, which was the previous behavior before
> it was suggested to follow SQL behavior.
>
> Together with another submitted patch about retrieving query results,
> the added capabilities allow to implement strictly conforming TPC-B
> transactions.

This patch applies cleanly and compiles at cccbdde with some whitespace
issues.

$ patch -p1 < ../other/pgbench-more-ops-funcs-9.patch
(Stripping trailing CRs from patch.)
patching file doc/src/sgml/ref/pgbench.sgml
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/exprparse.y
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/exprscan.l
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/pgbench.c
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/pgbench.h
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/t/002_pgbench.pl

Any reviewers want to have a look?

--
-David
david(at)pgmasters(dot)net

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