float4 smlar(anyarray, anyarray)
- computes similary of two arrays. Arrays should be the same type.
float4 smlar(anyarray, anyarray, bool useIntersect)
- computes similary of two arrays of composite types. Composite type looks like:
CREATE TYPE type_name AS (element_name anytype, weight_name FLOAT4);
useIntersect option points to use only intersected elements in denominator
see an exmaples in sql/composite_int4.sql or sql/composite_text.sql
float4 smlar( anyarray a, anyarray b, text formula );
- computes similary of two arrays by given formula, arrays should
be the same type.
Predefined variables in formula:
N.i - number of common elements in both array (intersection)
N.a - number of uniqueelements in first array
N.b - number of uniqueelements in second array
Example:
smlar('{1,4,6}'::int[], '{5,4,6}' )
smlar('{1,4,6}'::int[], '{5,4,6}', 'N.i / sqrt(N.a * N.b)' )
That calls are equivalent.
anyarray % anyarray
- returns true if similarity of that arrays is greater than limit
float4 show_smlar_limit() - deprecated
- shows the limit for % operation
float4 set_smlar_limit(float4) - deprecated
- sets the limit for % operation
Use instead of show_smlar_limit/set_smlar_limit GUC variable
smlar.threshold (see below)
text[] tsvector2textarray(tsvector)
- transforms tsvector type to text array
anyarray array_unique(anyarray)
- sort and unique array
float4 inarray(anyarray, anyelement)
- returns zero if second argument does not present in a first one
and 1.0 in opposite case
float4 inarray(anyarray, anyelement, float4, float4)
- returns fourth argument if second argument does not present in
a first one and third argument in opposite case
GUC configuration variables:
smlar.threshold FLOAT
Arrays with similarity lower than threshold are not similar
by % operation
smlar.persistent_cache BOOL
Cache of global stat is stored in transaction-independent memory
smlar.type STRING
Type of similarity formula: cosine(default), tfidf, overlap
smlar.stattable STRING
Name of table stored set-wide statistic. Table should be
defined as
CREATE TABLE table_name (
value data_type UNIQUE,
ndoc int4 (or bigint) NOT NULL CHECK (ndoc>0)
);
And row with null value means total number of documents.
See an examples in sql/*g.sql files
Note: used on for smlar.type = 'tfidf'
smlar.tf_method STRING
Calculation method for term frequency. Values:
"n" - simple counting of entries (default)
"log" - 1 + log(n)
"const" - TF is equal to 1
Note: used on for smlar.type = 'tfidf'
smlar.idf_plus_one BOOL
If false (default), calculate idf as log(d/df),
if true - as log(1+d/df)
Note: used on for smlar.type = 'tfidf'
Module provides several GUC variables smlar.threshold, it's highly
recommended to add to postgesql.conf:
custom_variable_classes = 'smlar' # list of custom variable class names
smlar.threshold = 0.6 #or any other value > 0 and < 1
and other smlar.* variables
GiST/GIN support for % and && operations for:
Array Type | GIN operator class | GiST operator class
---------------+----------------------+----------------------
bit[] | _bit_sml_ops |
bytea[] | _bytea_sml_ops | _bytea_sml_ops
char[] | _char_sml_ops | _char_sml_ops
cidr[] | _cidr_sml_ops | _cidr_sml_ops
date[] | _date_sml_ops | _date_sml_ops
float4[] | _float4_sml_ops | _float4_sml_ops
float8[] | _float8_sml_ops | _float8_sml_ops
inet[] | _inet_sml_ops | _inet_sml_ops
int2[] | _int2_sml_ops | _int2_sml_ops
int4[] | _int4_sml_ops | _int4_sml_ops
int8[] | _int8_sml_ops | _int8_sml_ops
interval[] | _interval_sml_ops | _interval_sml_ops
macaddr[] | _macaddr_sml_ops | _macaddr_sml_ops
money[] | _money_sml_ops |
numeric[] | _numeric_sml_ops | _numeric_sml_ops
oid[] | _oid_sml_ops | _oid_sml_ops
text[] | _text_sml_ops | _text_sml_ops
time[] | _time_sml_ops | _time_sml_ops
timestamp[] | _timestamp_sml_ops | _timestamp_sml_ops
timestamptz[] | _timestamptz_sml_ops | _timestamptz_sml_ops
timetz[] | _timetz_sml_ops | _timetz_sml_ops
varbit[] | _varbit_sml_ops |
varchar[] | _varchar_sml_ops | _varchar_sml_ops