F.10. intarray

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).

F.10.1. Functions

F.10.2. Operations

Table F-7. Operations

OperatorDescription
int[] && int[]overlap - returns TRUE if arrays have at least one common element
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[]returns the number of elements in array
int[] + intpush element to array ( add to end of array)
int[] + int[] merge of arrays (right array added to the end of left one)
int[] - intremove entries matched by right argument from array
int[] - int[]remove right array from left
int[] | intreturns 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[]returns TRUE if array satisfies query (commutator of @@)

(Before PostgreSQL 8.2, the containment operators @> and <@ were respectively called @ and ~. These names are still available, but are deprecated and will eventually be retired. Notice that the old names are reversed from the convention formerly followed by the core geometric datatypes!)

F.10.3. Example

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;
  

F.10.4. 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 -c -s 1,2 -v
     b)test with RD-Tree
       ./bench.pl -d TEST -c -s 1,2 -v -r

     BENCHMARKS:
    
     Size of table <message>: 200000
     Size of table <message_section_map>: 269133
    
     Distribution of messages by sections:
    
     section 0: 74377 messages
     section 1: 16284 messages
     section 50: 1229 messages
     section 99: 683 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|  0.625|  0.101|       -|      -|
     +----------+-------+-------+--------+-------+
     |        99|  0.018|  0.017|       -|      -|
     +----------+-------+-------+--------+-------+
     |       1,2|  0.766|  0.133|   0.628|  0.045|
     +----------+-------+-------+--------+-------+
     | 1,2,50,65|  0.794|  0.141|   0.030|  0.006|
     +----------+-------+-------+--------+-------+
  

F.10.5. Authors

All work was done by Teodor Sigaev () and Oleg Bartunov (). See http://www.sai.msu.su/~megera/postgres/gist for additional information. Andrey Oktyabrski did a great work on adding new functions and operations.