NAME
ElasticSearch::SearchBuilder - A Perlish compact query language for
ElasticSearch
VERSION
Version 0.01
DESCRIPTION
The Query DSL for ElasticSearch (see
<http://www.elasticsearch.org/guide/reference/query-dsl>), which is used
to write queries and filters, is simple but verbose, which can make it
difficult to write and understand large queries.
ElasticSearch::SearchBuilder is an SQL::Abstract-like query language
which exposes the full power of the query DSL, but in a more compact,
Perlish way.
SYNOPSIS
my $sb = ElasticSearch::SearchBuilder->new();
my $query = $sb->query({
body => {text => 'interesting keywords'},
-filter => {
status => 'active',
tags => ['perl','python','ruby'],
created => {
'>=' => '2010-01-01',
'<' => '2011-01-01'
},
}
})
METHODS
new()
my $sb = ElastiSearch::SearchBuilder->new()
Creates a new instance of the SearchBuilder - takes no parameters.
query()
my $es_query = $sb->query($compact_query)
Returns a query in the ElasticSearch query DSL.
$compact_query can be a scalar, a hash ref or an array ref.
$sb->query('foo')
# { "query" : { "text" : { "_all" : "foo" }}}
$sb->query({ ... }) or $sb->query([ ... ])
# { "query" : { ... }}
filter()
my $es_filter = $sb->filter($compact_filter)
Returns a filter in the ElasticSearch query DSL.
$compact_filter can be a scalar, a hash ref or an array ref.
$sb->filter('foo')
# { "filter" : { "term" : { "_all" : "foo" }}}
$sb->filter({ ... }) or $sb->filter([ ... ])
# { "filter" : { ... }}
INTRODUCTION
IMPORTANT: If you are not familiar with ElasticSearch then you should
read "ELASTICSEARCH CONCEPTS" before continuing.
This module was inspired by SQL::Abstract but they are not compatible
with each other.
All constructs described below can be applied to both queries and
filters, unless stated otherwise. If using the method "-query" then it
starts off in "query" mode, and if using the method "-filter" then it
starts off in filter mode. For example:
$sb->query({
# query mode
foo => 1,
bar => 2,
-filter => {
# filter mode
foo => 1,
bar => 2,
-query => {
# query mode
foo => 1
}
}
})
The easiest way to explain how the syntax works is to give examples:
KEY-VALUE PAIRS
Key-value pairs are converted to term queries or term filters:
# Field 'foo' contains term 'bar'
{ foo => 'bar' }
# Field 'foo' contains 'bar' or 'baz'
{ foo => ['bar','baz']}
# Field 'foo' contains terms 'bar' AND 'baz'
{ foo => ['-and','bar','baz']}
### FILTER ONLY ###
# Field 'foo' is missing ie has no value
{ foo => undef }
AND/OR LOGIC
Arrays are OR'ed, hashes are AND'ed:
# tags = 'perl' AND status = 'active:
{
tags => 'perl',
status => 'active'
}
# tags = 'perl' OR status = 'active:
[
tags => 'perl',
status => 'active'
]
# tags = 'perl' or tags = 'python':
{ tags => [ 'perl','python' ]}
{ tags => { '=' => [ 'perl','python' ] }}
# tags begins with prefix 'p' or 'r'
{ tags => { '^' => [ 'p','r' ] }}
The logic in an array can changed from OR to AND by making the first
element of the array ref "-and":
# tags has term 'perl' AND 'python'
{ tags => ['-and','perl','python']}
{
tags => [
-and => { '=' => 'perl'},
{ '=' => 'python'}
]
}
However, the first element in an array ref which is used as the value
for a field operator (see </"FIELD OPERATORS">) is not special:
# WRONG
{ tags => { '=' => [ '-and','perl','python' ] }}
...otherwise you would never be able to search for the term "-and". So
if you might possibly have the terms "-and" or "-or" in your data, use:
{ foo => {'=' => [....] }}
instead of:
{ foo => [....]}
Also, see "NESTING AND COMBINING".
FIELD OPERATORS
Most operators (eg "=", "gt", "geo_distance" etc) are applied to a
particular field. These are known as "Field Operators". For example:
# Field foo contains the term 'bar'
{ foo => 'bar' }
{ foo => {'=' => 'bar' }}
# Field created is between Jan 1 and Dec 31 2010
{ created => {
'>=' => '2010-01-01',
'<' => '2011-01-01'
}}
# Field foo contains terms which begin with prefix 'a' or 'b' or 'c'
{ foo => { '^' => ['a','b','c' ]}}
Some field operators are available as symbols (eg "=", "*", "^", "gt")
and others as words (eg "geo_distance" or "-geo_distance" - the dash is
optional).
Multiple field operators can be applied to a single field. Use "{}" to
imply "this AND that":
# Field foo has any value from 100 to 200
{ foo => { gte => 100, lte => 200 }}
# Field foo begins with 'p' but is not python
{ foo => {
'^' => 'p',
'!=' => 'python'
}}
Or "[]" to imply "this OR that"
# foo is 5 or foo greater than 10
{ foo => [
{ '=' => 5 },
{ 'gt' => 10 }
]}
All word operators may be negated by adding "not_" to the beginning, eg:
# Field foo does NOT contain a term beginning with 'bar' or 'baz'
{ foo => { not_prefix => ['bar','baz'] }}
UNARY OPERATORS
There are other operators which don't fit this "{ field => { op =>
value}}"model.
For instance:
* An operator might apply to multiple fields:
# Search fields 'title' and 'content' for text 'brown cow'
{
-query_string => {
query => 'brown cow',
fields => ['title','content']
}
}
* The field might BE the value:
# Find documents where the field 'foo' is blank or undefined
{ -missing => 'foo' }
# Find documents where the field 'foo' exists and has a value
{ -exists => 'foo' }
* For combining other queries or filters:
# Field foo has terms 'bar' and 'baz' but not 'balloo'
{
-and => [
foo => 'bar',
foo => 'baz',
-not => { foo => 'balloo' }
]
}
* Other:
# Script query
{ -script => "doc['num1'].value > 1" }
These operators are called "unary operators" and ALWAYS begin with a
dash "-" to distinguish them from field names.
Unary operators may also be prefixed with "not_" to negate their
meaning.
TERM QUERIES / FILTERS
= | == | in | != | <> | not_in
# Field foo has the term 'bar':
{ foo => 'bar' }
{ foo => { '=' => 'bar' }}
{ foo => { '==' => 'bar' }}
{ foo => { 'in' => 'bar' }}
# Field foo has the term 'bar' or 'baz'
{ foo => ['bar','baz'] }
{ foo => { '=' => ['bar','baz'] }}
{ foo => { '==' => ['bar','baz'] }}
{ foo => { 'in' => ['bar','baz'] }}
# Field foo does not contain the term 'bar':
{ foo => { '!=' => 'bar' }}
{ foo => { 'not_in' => 'bar' }}
# Field foo contains neither 'bar' nor 'baz'
{ foo => { '!=' => ['bar','baz'] }}
{ foo => { 'not_in' => ['bar','baz'] }}
*** For queries only ***
# With query params
{ foo => {
'=' => {
value => 5,
boost => 2
}
}}
# With query params
{ foo => {
'=' => {
value => [5,6],
boost => 2,
minimum_match => 2,
}
}}
For term queries see:
<http://www.elasticsearch.org/guide/reference/query-dsl/term-query.html>
and
<http://www.elasticsearch.org/guide/reference/query-dsl/terms-query.html
>
For term filters see:
<http://www.elasticsearch.org/guide/reference/query-dsl/term-filter.html
> and
<http://www.elasticsearch.org/guide/reference/query-dsl/terms-filter.htm
l>
^ | prefix | not_prefix
# Field foo contains a term which begins with 'bar'
{ foo => { '^' => 'bar' }}
{ foo => { 'prefix' => 'bar' }}
# Field foo contains a term which begins with 'bar' or 'baz'
{ foo => { '^' => ['bar','baz'] }}
{ foo => { 'prefix' => ['bar','baz'] }}
# Field foo contains a term which begins with neither 'bar' nor 'baz'
{ foo => { 'not_prefix' => ['bar','baz'] }}
*** For queries only ***
# With query params
{ foo => {
'^' => {
value => 'bar',
boost => 2
}
}}
For the prefix query see
<http://www.elasticsearch.org/guide/reference/query-dsl/prefix-query.htm
l>.
For the prefix filter see
<http://www.elasticsearch.org/guide/reference/query-dsl/prefix-filter.ht
ml>
lt | gt | lte | gte | < | <= | >= | > | range | not_range
These operators imply a range query, which can be numeric or
alphabetical.
# Field foo contains terms between 'alpha' and 'beta'
{ foo => {
'gte' => 'alpha',
'lte' => 'beta'
}}
# Field foo contains numbers between 10 and 20
{ foo => {
'gte' => '10',
'lte' => '20'
}}
*** For queries only ***
# boost a range query
{ foo => {
range => {
gt => 5,
gte => 5,
lt => 10,
lte => 10,
boost => 2.0
}
}}
Note: for filter clauses, the "gt","gte","lt" and "lte" operators imply
a "range" filter, while the "<", "<=", ">" and ">=" operators imply a
"numeric_range" filter.
This does not mean that you should use the "numeric_range" version for
any field which contains numbers!
The "numeric_range" query should be used for numbers/datetimes which
have many distinct values, eg "ID" or "last_modified". If you have a
numeric field with few distinct values, eg "number_of_fingers" then it
is better to use a "range" filter.
See
<http://www.elasticsearch.org/guide/reference/query-dsl/range-filter.htm
l> and
<http://www.elasticsearch.org/guide/reference/query-dsl/numeric-range-fi
lter.html>.
For queries, both sets of operators produce "range" queries.
See
<http://www.elasticsearch.org/guide/reference/query-dsl/range-query.html
>
* | wildcard | not_wildcard
*** For queries only ***
A "wildcard" query does a term query, but applies shell globbing to find
matching terms. In other words "?" represents any single character,
while "*" represents zero or more characters.
# Field foo matches 'f?ob*'
{ foo => { '*' => 'f?ob*' }}
{ foo => { 'wildcard' => 'f?ob*' }}
# with a boost:
{ foo => {
'*' => { value => 'f?ob*', boost => 2.0 }
}}
{ foo => {
'wildcard' => {
value => 'f?ob*',
boost => 2.0
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/wildcard-query.h
tml>
fuzzy | not_fuzzy
*** For queries only ***
A "fuzzy" query searches for terms that are similar to the the provided
terms, where similarity is based on the Levenshtein (edit distance)
algorithm:
# Field foo is similar to 'fonbaz'
{ foo => { fuzzy => 'fonbaz' }}
# With other parameters:
{ foo => {
fuzzy => {
value => 'fonbaz',
boost => 2.0,
min_similarity => 0.2,
max_expansions => 10
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/fuzzy-query.html
>.
MISSING / EXISTS
You can use a "missing" or "exists" filter to select only docs where a
particular field exists and has a value, or is undefined or has no
value:
*** For filters only ***
# Field 'foo' has a value:
{ foo => { exists => 1 }}
{ foo => { missing => 0 }}
{ -exists => 'foo' }
# Field 'foo' is undefined or has no value:
{ foo => { missing => 1 }}
{ foo => { exists => 0 }}
{ -missing => 'foo' }
{ foo => undef }
See
<http://www.elasticsearch.org/guide/reference/query-dsl/missing-filter.h
tml> and
<http://www.elasticsearch.org/guide/reference/query-dsl/exists-filter.ht
ml>
FULL TEXT SEARCH QUERIES
There are a range of full text search queries available, with varying
power, flexibility and complexity.
"Full text search" means that the text that you search on is analyzed
into terms before it is used by ElasticSearch.
See </"ELASTICSEARCH CONCEPTS"> for more.
*** For queries only ***
text | not_text
Perform a "text" query on a field. "text" queries are very flexible. For
analyzed text fields, they apply the correct analyzer and do a full text
search. For non-analyzed fields (numeric, date and non-analyzed strings)
it performs term queries:
# Non-analyzed field 'status' has the term 'active'
{ status => {text => 'active' }}
# Analyzed field 'content' includes the text "Brown Fox"
{ content => {text => 'Brown Fox' }}
# Same as above but with extra parameters:
{ content => {
text => {
query => 'Brown Fox',
boost => 2.0,
operator => 'and',
analyzer => 'default',
fuzziness => 0.5,
max_expansions => 100,
prefix_length => 2,
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/text-query.html>
phrase | not_phrase
Performs a "text_phrase" query. For instance "Brown Fox" will only match
if the phrase "brown fox" is present. Neither "fox brown" nor "Brown
Wiley Fox" will match.
{ content => { phrase=> "Brown Fox" }}
It accepts a "slop" factor which will preserve the word order, but allow
the words themselves to have other words inbetween. For instance, a
"slop" of 3 will allow "Brown Wiley Fox" to match, but "fox brown" still
won't match.
{ content => {
phrase => {
query => "Brown Fox",
slop => 3,
analyzer => 'default',
boost => 3.0,
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/text-query.html>
phrase_prefix | not_phrase_prefix
Performs a "text_phrase_prefix" query. This is the sameas the "phrase"
query, but also does a "prefix" query on the last term, which is useful
for auto-complete.
{ content => { phrase_prefix => "Brown Fo" }}
With extra options
{ content => {
phrase_prefix => {
query => "Brown Fo",
slop => 3,
analyzer => 'default',
boost => 3.0,
max_expansions => 100,
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/text-query.html>
field | not_field | -query_string | -not_query_string
A "field" query or "query_string" query does a full text query on the
provided text, and (unlike "text", "phrase" or "phrase_prefix" queries)
exposes all of the power of the Lucene query string syntax (see
<http://lucene.apache.org/java/3_2_0/queryparsersyntax.html>).
"field" queries are used to search on a single field, while
"-query_string" queries are used to search on multiple fields.
# search field foo for "this AND that"
{ foo => { field => 'this AND that' }}
# With other parameters
{ foo => {
field => {
query => 'this AND that ',
default_operator => 'AND',
analyzer => 'default',
allow_leading_wildcard => 0,
lowercase_expanded_terms => 1,
enable_position_increments => 1,
fuzzy_prefix_length => 2,
fuzzy_min_sim => 0.5,
phrase_slop => 10,
boost => 2,
analyze_wildcard => 1,
auto_generate_phrase_queries => 0,
}
}}
# multi-field searches:
{ -query_string => {
query => 'this AND that ',
fields => ['title','content'],
default_operator => 'AND',
analyzer => 'default',
allow_leading_wildcard => 0,
lowercase_expanded_terms => 1,
enable_position_increments => 1,
fuzzy_prefix_length => 2,
fuzzy_min_sim => 0.5,
phrase_slop => 10,
boost => 2,
analyze_wildcard => 1,
auto_generate_phrase_queries => 0,
use_dis_max => 1,
tie_breaker => 0.7
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/field-query.html
> and
<http://www.elasticsearch.org/guide/reference/query-dsl/query-string-que
ry.html> for more.
mlt | not_mlt
An "mlt" or "more_like_this" query finds documents that are "like" the
specified text, where "like" means that it contains some or all of the
specified terms.
# Field foo is like "brown cow"
{ foo => { mlt => "brown cow" }}
# With other paramters:
{ foo => {
mlt => {
like_text => 'brown cow',
percent_terms_to_match => 0.3,
min_term_freq => 2,
max_query_terms => 25,
stop_words => ['the','and'],
min_doc_freq => 5,
max_doc_freq => 1000,
min_word_len => 0,
max_word_len => 20,
boost_terms => 2,
boost => 2.0,
}
}}
# multi fields
{ -mlt => {
like_text => 'brown cow',
fields => ['title','content']
percent_terms_to_match => 0.3,
min_term_freq => 2,
max_query_terms => 25,
stop_words => ['the','and'],
min_doc_freq => 5,
max_doc_freq => 1000,
min_word_len => 0,
max_word_len => 20,
boost_terms => 2,
boost => 2.0,
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/mlt-field-query.
html> and
<http://www.elasticsearch.org/guide/reference/query-dsl/mlt-query.html>
flt | not_flt
An "flt" or "fuzzy_like_this" query fuzzifies all specified terms, then
picks the best "max_query_terms" differentiating terms. It is a
combination of "fuzzy" with "more_like_this".
# Field foo is fuzzily similar to "brown cow"
{ foo => { flt => 'brown cow }}
# With other parameters:
{ foo => {
flt => {
like_text => 'brown cow',
ignore_tf => 0,
max_query_terms => 10,
min_similarity => 0.5,
prefix_length => 3,
boost => 2.0,
}
}}
# Multi-field
flt => {
like_text => 'brown cow',
fields => ['title','content'],
ignore_tf => 0,
max_query_terms => 10,
min_similarity => 0.5,
prefix_length => 3,
boost => 2.0,
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/flt-field-query.
html> and
<http://www.elasticsearch.org/guide/reference/query-dsl/flt-query.html>
NESTING AND COMBINING
These constructs allow you to combine multiple queries and filters.
-filter
This allows you to combine a query with one or more filters:
*** For queries only ***
# query field content for 'brown cow', and filter documents
# where status is 'active' and tags contains the term 'perl'
{
content => { text => 'brown cow' },
-filter => {
status => 'active',
tags => 'perl'
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/filtered-query.h
tml>
-query
This allows you to combine a filter with one or more queries:
*** For filters only ***
# query field content for 'brown cow', and filter documents
# where status is 'active', tags contains the term 'perl'
# and a text query on field title contains 'important'
{
content => { text => 'brown cow' },
-filter => {
status => 'active',
tags => 'perl',
-query => {
title => { text => 'important' }
}
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/query-filter.htm
l>
-and | -or | -not
These operators allow you apply "and", "or" and "not" logic to nested
queries or filters.
# Field foo has both terms 'bar' and 'baz'
{ -and => [
foo => 'bar',
foo => 'baz'
]}
# Field
{ -or => [
{ name => { text => 'John Smith' }},
{
-missing => 'name',
name => { text => 'John Smith' }
}
]}
The "-and", "-or" and "-not" constructs emit "and", "or" and "not"
filters for filters, and "bool" queries for queries.
See
<http://www.elasticsearch.org/guide/reference/query-dsl/bool-query.html>
,
"http://www.elasticsearch.org/guide/reference/query-dsl/and-filter.html"
,
"http://www.elasticsearch.org/guide/reference/query-dsl/or-filter.html"
and
"http://www.elasticsearch.org/guide/reference/query-dsl/not-filter.html"
.
-dis_max | -dismax
While a "bool" query adds together the scores of the nested queries, a
"dis_max" query uses the highest score of any matching queries.
*** For queries only ***
# Run the two queries and use the best score
{ -dismax => [
{ foo => 'bar' },
{ foo => 'baz' }
] }
# With other parameters
{ -dismax => {
queries => [
{ foo => 'bar' },
{ foo => 'baz' }
],
tie_breaker => 0.5,
boost => 2.0
] }
See
<http://www.elasticsearch.org/guide/reference/query-dsl/dis-max-query.ht
ml>
-bool
Normally, there should be no need to use a "bool" query directly, as
these are autogenerated from eg "-and", "-or" and "-not" constructs.
However, if you need to pass any of the other parameters to a "bool"
query, then you can do the following:
{
-bool => {
must => [{ foo => 'bar' }],
must_not => { status => 'inactive' },
should => [
{ tag => 'perl' },
{ tag => 'python' },
{ tag => 'ruby' },
],
minimum_number_should_match => 2,
disable_coord => 1,
boost => 2
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/bool-filter.html
>
-boosting
The "boosting" query can be used to "demote" results that match a given
query. Unlike the "must_not" clause of a "bool" query, the query still
matches, but the results are "less relevant".
{ -boosting => {
positive => { title => { text => 'apple pear' }},
negative => { title => { text => 'apple computer' }},
negative_boost => 0.2
}}
<http://www.elasticsearch.org/guide/reference/query-dsl/boosting-query.h
tml>
GEOLOCATION FILTERS
Geo-location filters work with fields that have the type "geo_point".
See
<http://www.elasticsearch.org/guide/reference/mapping/geo-point-type.htm
l>) for valid formats for the $location field.
*** For filters only ***
geo_distance | not_geo_distance
Return docs with $distance of $location:
# Field 'point' is within 100km of London
{ point => {
geo_distance => {
distance => '100km',
location => {
lat => 51.50853,
lon => -0.12574
}
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/geo-distance-fil
ter.html>
geo_distance_range | not_geo_distance_range
This is like the range filter, and accepts the same parameters:
# Field 'point' is 100-200km from London
{ point => {
geo_distance_range => {
gte => '100km',
lte => '200km',
location => {
lat => 51.50853,
lon => -0.12574
}
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/geo-distance-ran
ge-filter.html>
geo_bounding_box | not_geo_bounding_box
This returns documents whose location lies within the specified
rectangle:
{ point => {
geo_bounding_box => {
top_left => [40.73,-74.1],
bottom_right => [40.71,-73.99],
}
}}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/geo-bounding-box
-filter.html>
geo_polygon | not_geo_polygon
This finds documents whose location lies within the specified polygon:
{ point => {
geo_polygon => [[40,-70],[30,-80],[20,-90]]
}}
<http://www.elasticsearch.org/guide/reference/query-dsl/geo-polygon-filt
er.html>
SCRIPTING
ElasticSearch supports the use of scripts to customise query or filter
behaviour. By default the query language is "mvel" but javascript,
groovy, python and native java scripts are also supported.
See
<http://www.elasticsearch.org/guide/reference/modules/scripting.html>
for more on scripting.
-custom_score
The "-custom_score" query allows you to customise the "_score" or
relevance (and thus the order) of returned docs.
*** For queries only ***
{
-custom_score => {
query => { foo => 'bar' },
lang => 'mvel',
script => "_score * doc['my_numeric_field'].value / pow(param1, param2)"
params => {
param1 => 2,
param2 => 3.1
},
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/custom-score-que
ry.html>
-script
The "-script" filter allows you to use a script as a filter. Return a
true value to indicate that the filter matches.
*** For filters only ***
# Filter docs whose field 'foo' is greater than 5
{ -script => "doc['foo'].value > 5 " }
# With other params
{
-script => {
script => "doc['foo'].value > minimum ",
params => { minimum => 5 },
lang => 'mvel'
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/script-filter.ht
ml>
TYPE/IDS
The "_type" and "_id" fields are not indexed by default, and thus aren't
available for normal queries or filters.
-ids
Returns docs with the matching "_id" or "_id"/"_type" combination:
# doc with ID 123
{ -ids => 123 }
# docs with IDs 123 or 124
{ -ids => [123,124] }
# docs of types 'blog' or 'comment' with IDs 123 or 124
{
-ids => {
type => ['blog','comment'],
values => [123,124]
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/ids-query.html>
and
<http://www.elasticsearch.org/guide/reference/query-dsl/ids-filter.html>
-type
Filters docs with matching "_type" fields:
*** For filters only ***
# Filter docs of type 'comment'
{ -type => 'comment' }
# Filter docs of type 'comment' or 'blog'
{ -type => ['blog','comment' ]}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/type-filter.html
>
PARENT/CHILD
Documents stored in ElasticSearch can be configured to have parent/child
relationships.
See
<http://www.elasticsearch.org/guide/reference/mapping/parent-field.html>
for more.
has_child | not_has_child
Find parent documents that have child documents which match a query.
# Find parent docs whose children of type 'comment' have the tag 'perl'
{
-has_child => {
type => 'comment',
query => { tag => 'perl' },
_scope => 'my_scope',
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/has-child-query.
html> and
<http://www.elasticsearch.org/guide/reference/query-dsl/has-child-filter
.html>.
top_children
The "top_children" query runs a query against the child docs, and
aggregates the scores to find the parent docs whose children best match.
*** For queries only ***
{
-top_children => {
type => 'blog_tag',
query => { tag => 'perl' },
score => 'max',
factor => 5,
incremental_factor => 2,
_scope => 'my_scope'
}
}
See
<http://www.elasticsearch.org/guide/reference/query-dsl/top-children-que
ry.html>
CACHING FILTERS
Part of the performance boost that you get when using filters comes from
the ability to cache the results of those filters. However, it doesn't
make sense to cache all filters by default.
If you would like to override the default caching, then you can use
"-cache" or "-nocache":
# Don't cache the term filter for 'status'
{
content => { text => 'interesting post'},
-filter => {
-nocache => { status => 'active' }
}
}
# Do cache the numeric range filter:
{
content => { text => 'interesting post'},
-filter => {
-cache => { created => {'>' => '2010-01-01' } }
}
}
See <http://www.elasticsearch.org/guide/reference/query-dsl/> for more
details about what is cached by default and what is not.
ELASTICSEARCH CONCEPTS
Filters vs Queries
ElasticSearch supports filters and queries:
* A filter just answers the question: "Does this field match? Yes/No",
eg:
* Does this document have the tag "beta"?
* Was this document published in 2011?
* A query is used to calculate relevance ( known in ElasticSearch as
"_score"):
* Give me all documents that include the keywords "Foo" and "Bar"
and rank them in order of relevance.
* Give me all documents whose "tag" field contains "perl" or
"ruby" and rank documents that contain BOTH tags more highly.
Filters are lighter and faster, and the results can often be cached, but
they don't contribute to the "_score" in any way.
Typically, most of your clauses will be filters, and just a few will be
queries.
Terms vs Text
All data is stored in ElasticSearch as a "term", which is an exact
value. The term "Foo" is not the same as "foo".
While this is useful for fields that have discreet values (eg "active",
"inactive"), it is not sufficient to support full text search.
ElasticSearch has to *analyze* text to convert it into terms. This
applies both to the text that the stored document contains, and to the
text that the user tries to search on.
The default analyzer will:
* split the text on (most) punctuation and remove that punctuation
* lowercase each word
* remove English stopwords
For instance, "The 2 GREATEST widgets are foo-bar and fizz_buzz" would
result in the terms " [2,'greatest','widgets','foo','bar','fizz_buzz']".
It is important that the same analyzer is used both for the stored text
and for the search terms, otherwise the resulting terms may be
different, and the query won't succeed.
For instance, a "term" query for "GREATEST" wouldn't work, but
"greatest" would work. However, a "text" query for "GREATEST" would
work, because the search text would be analyzed into the correct terms.
See
<http://www.elasticsearch.org/guide/reference/index-modules/analysis/>
for the list of supported analyzers.
AUTHOR
Clinton Gormley, "<drtech at cpan.org>"
BUGS
This is an alpha module, so there will be bugs, and the API is likely to
change in the future.
If you have any suggestions for improvements, or find any bugs, please
report them to
<https://github.com/clintongormley/ElasticSearch-SearchBuilder/issues>.
I will be notified, and then you'll automatically be notified of
progress on your bug as I make changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc ElasticSearch::SearchBuilder
You can also look for information at: <http://www.elasticsearch.org>
ACKNOWLEDGEMENTS
Thanks to SQL::Abstract for providing the inspiration and some of the
internals.
LICENSE AND COPYRIGHT
Copyright 2011 Clinton Gormley.
This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.
See http://dev.perl.org/licenses/ for more information.