Re: Observation on integer types documentation

On Wed, Aug 29, 2012 at 06:38:47PM -0400, Bruce Momjian wrote:
>
> I have developed the attached patch based on your observations.

Applied.

---------------------------------------------------------------------------

>
> On Mon, Apr 30, 2012 at 03:59:20PM -0500, Dan McGee wrote:
> > Hey everyone,
> >
> > Reading the docs today, I came across this paragraph
> > (http://www.postgresql.org/docs/devel/static/datatype-numeric.html#DATATYPE-INT),
> > which goes back several major versions:
> >
> > > The type integer is the common choice, as it offers the best balance between range, storage size, and performance. The smallint type is generally only used if disk space is at a premium. The bigint type should only be used if the range of the integer type is insufficient, because the latter is definitely faster.
> >
> > A few thoughts on this.
> > 1) the use of the word "latter" isn't totally clear, or at least I had
> > to re-read it to realize former was 'bigint' and latter was 'integer'.
> > It might just be the style of writing.
> > 2) I'm less than convinced this note belongs in modern documentation,
> > and set out to test that theory. My full results are below, but the
> > summary is this: on a 64-bit system, there seems to be only a minimal
> > measurable performance difference (< 5%) and very little size
> > difference. In the case of the indexes, the size difference is zero.
> > This is not true for a 32-bit system (where it is 39% slower), but the
> > blanket statement doesn't hold true, which is why I'm writing all this
> > up.
> >
> > On a final note, the following paragraph also seems like it has
> > outlived its useful life:
> >
> > > On very minimal operating systems the bigint type might not function correctly, because it relies on compiler support for eight-byte integers. On such machines, bigint acts the same as integer, but still takes up eight bytes of storage. (We are not aware of any modern platform where this is the case.)
> >
> > Thanks!
> > -Dan
> >
> >
> > Table setup (only difference is type of 'id' column):
> >
> > Table "public.package_files"
> > Column | Type | Modifiers
> > --------------+------------------------+------------------------
> > id | integer | not null
> > pkg_id | integer | not null
> > is_directory | boolean | not null default false
> > directory | character varying(255) | not null
> > filename | character varying(255) |
> > Indexes:
> > "package_files_pkey" PRIMARY KEY, btree (id)
> > "package_files_pkg_id" btree (pkg_id) CLUSTER
> >
> >
> > Table "public.package_files_int8"
> > Column | Type | Modifiers
> > --------------+------------------------+------------------------
> > id | bigint | not null
> > pkg_id | integer | not null
> > is_directory | boolean | not null default false
> > directory | character varying(255) | not null
> > filename | character varying(255) |
> > Indexes:
> > "package_files_int8_pkey" PRIMARY KEY, btree (id)
> > "package_files_int8_pkg_id" btree (pkg_id) CLUSTER
> >
> >
> > # select count(*) from package_files;
> > 2621418
> > # select count(*) from package_files_int8 ;
> > 2621418
> >
> >
> > All runs below were done after issuing a few warm up queries, and both
> > tables went through a VACUUM/CLUSTER/ANALYZE sequence.
> >
> > 32-bit P4 2.4 GHz (single core). no enabled CPU frequency scaling, 1GB
> > total ram, shared_buffers 128MB, work_mem 4MB:
> >
> > relation | size
> > ----------------------------------+------------
> > public.package_files_int8 | 239 MB
> > public.package_files | 229 MB
> > public.package_files_int8_pkey | 56 MB
> > public.package_files_int8_pkg_id | 45 MB
> > public.package_files_pkey | 45 MB
> > public.package_files_pkg_id | 45 MB
> >
> > archweb=> \timing on
> > Timing is on.
> > archweb=> \t
> > Showing only tuples.
> > archweb=> select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 516.558 ms
> > archweb=> select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 519.720 ms
> > archweb=> select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 533.330 ms
> > archweb=> select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 519.095 ms
> > archweb=> select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 520.253 ms
> >
> > archweb=> select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 731.194 ms
> > archweb=> select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 730.329 ms
> > archweb=> select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 724.646 ms
> > archweb=> select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 710.815 ms
> > archweb=> select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 724.519 ms
> >
> >
> >
> >
> > 64-bit Core2 Quad 2.66 GHz (four core), CPU freq scaling disabled
> > (performance governor used), 8GB total ram, shared_buffers 128MB,
> > work_mem 4MB:
> >
> > relation | size
> > ----------------------------------+------------
> > public.package_files_int8 | 245 MB
> > public.package_files | 234 MB
> > public.package_files_int8_pkey | 56 MB
> > public.package_files_pkg_id | 56 MB
> > public.package_files_int8_pkg_id | 56 MB
> > public.package_files_pkey | 56 MB
> >
> > dmcgee=# select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 177.078 ms
> > dmcgee=# select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 176.109 ms
> > dmcgee=# select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 177.478 ms
> > dmcgee=# select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 176.639 ms
> > dmcgee=# select count(*) from (select * from package_files where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 176.453 ms
> >
> > dmcgee=# select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 185.768 ms
> > dmcgee=# select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 185.159 ms
> > dmcgee=# select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 184.407 ms
> > dmcgee=# select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 184.555 ms
> > dmcgee=# select count(*) from (select * from package_files_int8 where
> > pkg_id in (48024, 48025, 40343) order by id) a;
> > 119325
> > Time: 184.290 ms
> >
> >
> > Overall results:
> >
> > i686 x86_64
> > int4 int8 int4 int8
> > 516.558 731.194 177.078 185.768
> > 519.72 730.329 176.109 185.159
> > 533.33 724.646 177.478 184.407
> > 519.095 710.815 176.639 184.555
> > 520.253 724.519 176.453 184.29
> >
> >
> >
> > Average 521.7912 724.3006 176.7514 184.8358
> > Stddev 6.6040841681 8.1530512264 0.5359499044 0.619288059
> > Ratio 1.3881042839 1.0457388173
> >
> > --
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> > To make changes to your subscription:
> > http://www.postgresql.org/mailpref/pgsql-docs
>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://enterprisedb.com
>
> + It's impossible for everything to be true. +

> diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
> new file mode 100644
> index 7f6e661..71cf59e
> *** a/doc/src/sgml/datatype.sgml
> --- b/doc/src/sgml/datatype.sgml
> ***************
> *** 453,470 ****
> The type <type>integer</type> is the common choice, as it offers
> the best balance between range, storage size, and performance.
> The <type>smallint</type> type is generally only used if disk
> ! space is at a premium. The <type>bigint</type> type should only
> ! be used if the range of the <type>integer</type> type is insufficient,
> ! because the latter is definitely faster.
> ! </para>
> !
> ! <para>
> ! On very minimal operating systems the <type>bigint</type> type
> ! might not function correctly, because it relies on compiler support
> ! for eight-byte integers. On such machines, <type>bigint</type>
> ! acts the same as <type>integer</type>, but still takes up eight
> ! bytes of storage. (We are not aware of any modern
> ! platform where this is the case.)
> </para>
>
> <para>
> --- 453,460 ----
> The type <type>integer</type> is the common choice, as it offers
> the best balance between range, storage size, and performance.
> The <type>smallint</type> type is generally only used if disk
> ! space is at a premium. The <type>bigint</type> type is designed to be
> ! used when the range of the <type>integer</type> type is insufficient.
> </para>
>
> <para>

>
> --
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> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-docs

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +