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
	Array's 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