dbsize

% cd src/postgresql-7.3.4/contrib/dbsize
% make
sed 's,MODULE_PATHNAME,$libdir/dbsize,g' dbsize.sql.in >dbsize.sql
gcc -O2 -Wall -Wmissing-prototypes -Wmissing-declarations -fpic -I. -I../../src/include   -c -o dbsize.o dbsize.c
gcc -shared -o dbsize.so dbsize.o
rm dbsize.o
%

# make install

mkdir /usr/local/pgsql/share/contrib

mkdir /usr/local/pgsql/doc/contrib

/bin/sh ../../config/install-sh -c -m 644 dbsize.sql /usr/local/pgsql/share/contrib

 /bin/sh ../../config/install-sh -c -m 755  dbsize.so /usr/local/pgsql/lib

/bin/sh ../../config/install-sh -c -m 644 ./README.dbsize /usr/local/pgsql/doc/contrib

#

% less dbsize.sql

CREATE FUNCTION database_size (name) RETURNS bigint

    AS '$libdir/dbsize', 'database_size'

    LANGUAGE C WITH (isstrict);

CREATE FUNCTION relation_size (text) RETURNS bigint

    AS '$libdir/dbsize', 'relation_size'

    LANGUAGE C WITH (isstrict);

% psql -U postgres testdb -f dbsize.sql

CREATE FUNCTION

CREATE FUNCTION

% psql testdb postgres

Welcome to psql 7.3.4, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms

       \h for help with SQL commands

       \? for help on internal slash commands

       \g or terminate with semicolon to execute query

       \q to quit

testdb=> SELECT database_size('testdb');

 database_size

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

      31813876

(1 row)

testdb=>

DB サイズは 31,813,876 bytes

% bc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
31813876/8192
3883

8kbytes で割ると、共有バッファ 3883 必要ということになる。