postgresql/contrib/intarray/README.intarray

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This is an implementation of RD-tree data structure using GiST interface
of PostgreSQL. It has built-in lossy compression.
Current implementation provides index support for one-dimensional array of
int4's - gist__int_ops, suitable for small and medium size of arrays (used on
default), and gist__intbig_ops for indexing large arrays (we use superimposed
signature with length of 4096 bits to represent sets).
All work was done by Teodor Sigaev (teodor@stack.net) and Oleg Bartunov
(oleg@sai.msu.su). See http://www.sai.msu.su/~megera/postgres/gist
for additional information. Andrey Oktyabrski did a great work on
adding new functions and operations.
FUNCTIONS:
int icount(int[]) - the number of elements in intarray
test=# select icount('{1,2,3}'::int[]);
icount
--------
3
(1 row)
int[] sort(int[], 'asc' | 'desc') - sort intarray
test=# select sort('{1,2,3}'::int[],'desc');
sort
---------
{3,2,1}
(1 row)
int[] sort(int[]) - sort in ascending order
int[] sort_asc(int[]),sort_desc(int[]) - shortcuts for sort
int[] uniq(int[]) - returns unique elements
test=# select uniq(sort('{1,2,3,2,1}'::int[]));
uniq
---------
{1,2,3}
(1 row)
int idx(int[], int item) - returns index of first intarray matching element to item, or
'0' if matching failed.
test=# select idx('{1,2,3,2,1}'::int[],2);
idx
-----
2
(1 row)
int[] subarray(int[],int START [, int LEN]) - returns part of intarray starting from
element number START (from 1) and length LEN.
test=# select subarray('{1,2,3,2,1}'::int[],2,3);
subarray
----------
{2,3,2}
(1 row)
int[] intset(int4) - casting int4 to int[]
test=# select intset(1);
intset
--------
{1}
(1 row)
OPERATIONS:
int[] && int[] - overlap - returns TRUE if arrays has at least one common elements.
int[] @ int[] - contains - returns TRUE if left array contains right array
int[] ~ int[] - contained - returns TRUE if left array is contained in right array
# int[] - return the number of elements in array
int[] + int - push element to array ( add to end of array)
int[] + int[] - merge of arrays (right array added to the end of left one)
int[] - int - remove entries matched by right argument from array
int[] - int[] - remove right array from left
int[] | int - returns intarray - union of arguments
int[] | int[] - returns intarray as a union of two arrays
int[] & int[] - returns intersection of arrays
int[] @@ query_int - returns TRUE if array satisfies query (like '1&(2|3)')
query_int ~~ int[] - -/-
CHANGES:
August 6, 2002
1. Reworked patch from Andrey Oktyabrski (ano@spider.ru) with
functions: icount, sort, sort_asc, uniq, idx, subarray
operations: #, +, -, |, &
October 1, 2001
1. Change search method in array to binary
September 28, 2001
1. gist__int_ops now is without lossy
2. add sort entry in picksplit
September 21, 2001
1. Added support for boolean query (indexable operator @@, looks like
a @@ '1|(2&3)', perfomance is better in any case )
2. Done some small optimizations
March 19, 2001
1. Added support for toastable keys
2. Improved split algorithm for intbig (selection speedup is about 30%)
INSTALLATION:
gmake
gmake install
-- load functions
psql <database> < _int.sql
REGRESSION TEST:
gmake installcheck
EXAMPLE USAGE:
create table message (mid int not null,sections int[]);
create table message_section_map (mid int not null,sid int not null);
-- create indices
CREATE unique index message_key on message ( mid );
CREATE unique index message_section_map_key2 on message_section_map (sid, mid );
CREATE INDEX message_rdtree_idx on message using gist ( sections gist__int_ops);
-- select some messages with section in 1 OR 2 - OVERLAP operator
select message.mid from message where message.sections && '{1,2}';
-- select messages contains in sections 1 AND 2 - CONTAINS operator
select message.mid from message where message.sections @ '{1,2}';
-- the same, CONTAINED operator
select message.mid from message where '{1,2}' ~ message.sections;
BENCHMARK:
subdirectory bench contains benchmark suite.
cd ./bench
1. createdb TEST
2. psql TEST < ../_int.sql
3. ./create_test.pl | psql TEST
4. ./bench.pl - perl script to benchmark queries, supports OR, AND queries
with/without RD-Tree. Run script without arguments to
see availbale options.
a)test without RD-Tree (OR)
./bench.pl -d TEST -s 1,2 -v
b)test with RD-Tree
./bench.pl -d TEST -s 1,2 -v -r
BENCHMARKS:
Size of table <message>: 200000
Size of table <message_section_map>: 268538
Distribution of messages by sections:
section 0: 73899 messages
section 1: 16298 messages
section 50: 1241 messages
section 99: 705 messages
old - without RD-Tree support,
new - with RD-Tree
+----------+---------------+----------------+
|Search set|OR, time in sec|AND, time in sec|
| +-------+-------+--------+-------+
| | old | new | old | new |
+----------+-------+-------+--------+-------+
| 1| 1.427| 0.215| -| -|
+----------+-------+-------+--------+-------+
| 99| 1.029| 0.018| -| -|
+----------+-------+-------+--------+-------+
| 1,2| 1.829| 0.334| 5.654| 0.042|
+----------+-------+-------+--------+-------+
| 1,2,50,60| 2.057| 0.359| 5.044| 0.007|
+----------+-------+-------+--------+-------+