92 lines
3.0 KiB
Plaintext
92 lines
3.0 KiB
Plaintext
This is an implementation of RD-tree data structure using GiST interface
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of PostgreSQL. It has built-in lossy compression - must be declared
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in index creation - with (islossy). Current implementation provides index
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support for one-dimensional array of int4's - gist__int_ops, suitable for
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small and medium size of arrays (used on default), and gist__intbig_ops for
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indexing large arrays (we use superimposed signature with length of 4096
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bits to represent sets).
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All work was done by Teodor Sigaev (teodor@stack.net) and Oleg Bartunov
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(oleg@sai.msu.su). See http://www.sai.msu.su/~megera/postgres/gist
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for additional information.
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CHANGES:
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March 19, 2001
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1. Added support for toastable keys
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2. Improved split algorithm for intbig (selection speedup is about 30%)
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INSTALLATION:
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gmake
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gmake install
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-- load functions
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psql <database> < _int.sql
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REGRESSION TEST:
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gmake installcheck
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EXAMPLE USAGE:
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create table message (mid int not null,sections int[]);
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create table message_section_map (mid int not null,sid int not null);
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-- create indices
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CREATE unique index message_key on message ( mid );
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CREATE unique index message_section_map_key2 on message_section_map (sid, mid );
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CREATE INDEX message_rdtree_idx on message using gist ( sections gist__int_ops) with ( islossy );
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-- select some messages with section in 1 OR 2 - OVERLAP operator
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select message.mid from message where message.sections && '{1,2}';
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-- select messages contains in sections 1 AND 2 - CONTAINS operator
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select message.mid from message where message.sections @ '{1,2}';
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-- the same, CONTAINED operator
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select message.mid from message where '{1,2}' ~ message.sections;
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BENCHMARK:
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subdirectory bench contains benchmark suite.
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cd ./bench
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1. createdb TEST
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2. psql TEST < ../_int.sql
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3. ./create_test.pl | psql TEST
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4. ./bench.pl - perl script to benchmark queries, supports OR, AND queries
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with/without RD-Tree. Run script without arguments to
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see availbale options.
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a)test without RD-Tree (OR)
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./bench.pl -d TEST -s 1,2 -v
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b)test with RD-Tree
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./bench.pl -d TEST -s 1,2 -v -r
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BENCHMARKS:
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Size of table <message>: 200000
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Size of table <message_section_map>: 268538
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Distribution of messages by sections:
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section 0: 73899 messages
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section 1: 16298 messages
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section 50: 1241 messages
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section 99: 705 messages
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old - without RD-Tree support,
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new - with RD-Tree
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+----------+---------------+----------------+
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|Search set|OR, time in sec|AND, time in sec|
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| +-------+-------+--------+-------+
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| | old | new | old | new |
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+----------+-------+-------+--------+-------+
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| 1| 1.427| 0.215| -| -|
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+----------+-------+-------+--------+-------+
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| 99| 1.029| 0.018| -| -|
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+----------+-------+-------+--------+-------+
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| 1,2| 1.829| 0.334| 5.654| 0.042|
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+----------+-------+-------+--------+-------+
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| 1,2,50,60| 2.057| 0.359| 5.044| 0.007|
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+----------+-------+-------+--------+-------+
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