Elasticsearch: Query Basics
Han Yi
April 30, 2018
RESTful API of Search
- Basic Search
- URI based search
- Request body based search
GET products/_doc/_search?q=rating:5
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"score_mode":"max",
"query":{
"simple_query_string":{
"query":"red hat",
"fields":[
"child.color^2.0",
"child.name^1.0",
]
}
}
}
}
}
Filter and Query Context
- Filter Context
- Does this document match this query clause?
- case 1: bool filter/must_not
- case 2: constant_score filter
- case 3: aggregation filter
- case 4: score functions
- Query Context
- How well does this document match this query clause?
Filter Context Examples
//1. filter inner bool query
POST context/_doc/_search
{
"query": {
"bool": {
"must": {
"match": {
"name": "red hat"
}
},
"filter": {
"term": {
"context": "generic"
}
}
}
}
}
//2. constant_score
POST products/_doc/_search
{
"query": {
"constant_score": {
"filter": {
"term": {
"status": "active"
}
}
}
}
}
//3. aggregation filter
POST products/_doc/_search
{
"aggs": {
"nested_aggs": {
"nested": {
"path":"child"
},
"aggs": {
"filtered_aggs": {
"filter": {
"bool": {
"must": [
{
"term": {
"child.color":"red"
}
}
]
}
},
"aggs": {
"lvl": {
"terms": {
"field": "child.lvl",
"order": {
"count":"desc"
}
},
"aggs": {
"count": {
"reverse_nested":{}
}
}
}
}
}
}
}
}
}
//4. Score functions
POST products/_doc/_search
{
"query": {
"function_score": {
"query": { "match_all": {} },
"boost": "5",
"functions": [
{
"filter": { "match": { "test": "bar" } },
"random_score": {},
"weight": 23
},
{
"filter": { "match": { "test": "cat" } },
"weight": 42
}
],
"max_boost": 42,
"score_mode": "max",
"boost_mode": "multiply",
"min_score" : 42
}
}
}
Pros and Cons of Filter Context
- Performance
- Caching
- Frequently used filters will be cached
- Cache is stored at the node level
- Default to be 10% of the heap
- Can be configured by indices.queries.cache.size: 10%
- No relevancy
Basic Query Patterns
- Term Level Query
- term(s), range, exists, prefix, wildcard, regexp, fuzzy, type, ids
- Full Text Query
- (multi) match (phrase), common terms, (simple) query string
- Compound Query
- constant score, bool, dis max, function score, boosting
Term Level Query
//1. term vs terms query
POST expmgrrules/doc/_search
{
"query": {
"term": {
"triggers": "26972"
}
}
}
POST expmgrrules/doc/_search
{
"query": {
"terms": {
"triggers": ["26972","20676"]
}
}
}
//2. range query
POST products/doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"range": {
"child.price": {
"lte": 5
}
}
}
}
}
}
//3. range with date query
POST products/doc/_search
{
"from": 0,
"size": 24,
"query": {
"nested": {
"path": "path",
"query": {
"range": {
"releaseDate": {
"gt": "now-1h"
}
}
}
}
}
}
//4. exists query
POST products/doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"exists": {
"field": "special"
}
}
}
}
}
//5. wildcard/regex query
//* means any match, ? means single match
POST products/doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"wildcard": {
"name": "boys*"
}
}
}
}
}
Term Level Query vs Full-Text Query
- Term vs Match
- Term level query can be used for numbers, booleans, dates, and text type field, but it ignores mapping types and only matches low-level exact terms inverted index
- Match allows to use mapping type for input query and document field, then build complex term level query to look up the inverted index
- Match by default use "should" to build term query, the user can use {"operator": "and"} to generate "must" term query
Full-Text Query: Match
//1. basic match
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"query":{
"match": {
"child.name": "men hat"
}
}
}
}
}
//2. complete match with the operator
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"query":{
"match": {
"child.name": {
"query": "men hat",
"operator": "AND"
}
}
}
}
}
}
//3. multi match
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"query":{
"multi_match": {
"query": "red hat",
"fields": ["child.name^1.0", "child.color^2.0"]
}
}
}
}
}
//4. match phrase
POST products/doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"match_phrase": {
"child.name": {
"query": "men hat",
"slop": 2
}
}
}
}
}
}
Full-Text Query: (Simple) Query String
//1. query string
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"score_mode":"max",
"query":{
"query_string":{
"query":"(red hat) OR (blue hat)",
"fields":[
"child.color^2.0",
"child.name^1.0",
]
}
}
}
}
}
//2. simple query string
POST products/_doc/_search
{
"query": {
"nested":{
"path":"child",
"score_mode":"max",
"query":{
"simple_query_string":{
"query":"(red hat) OR (blue hat)",
"fields":[
"child.color^2.0",
"child.name^1.0",
]
}
}
}
}
}
Full-Text Query: (Simple) Query String
- Query String Syntax
- Field names: "rating:(4 OR 5)"
- Wildcards: "g*l ha?"
- Regular expression: "name:/red.*hat/"
- Fuzziness: "synoyms~1"
- Proximity searches: "red hat~5"
- Ranges: "rating:[3 TO 5]"
- Boosting
- "color^2.0" or "red^2.0 hat"
- Boolean operators: "+red hat -shirt"
- Grouping: "(red OR blue) hat"
Full-Text Query: (Simple) Query String
-
Query String vs Simple Query String
- The query_string query parses the input and splits text around operators
- Each textual part is analyzed independently of each other
- Query string contains a lot of reserved characters, which could lead to a syntax error that prevents the query from running
- Unlike the regular query_string query, the Simple query string query will never throw an exception and just discards invalid parts of the query
Compound Query
- bool query structure
- must, must_not, should are in the scoring mode
- the filter is must match without scoring mode
{
"query": {
"bool": {
"must": [],
"must_not": [],
"should": [],
"filter": [],
}
}
}
Manual Intervention Scoring
- Multi match / Query string
- Function score query
- Compound query boost
- Rescore
- Debugging score calculation
- Pros and Cons of Query Context search
Function Score Query
- Modify the score of documents that are retrieved by a query
- Score function works on a filtered set of documents
GET products/_doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"function_score": {
"query": {
"match": {
"child.color": "red"
}
},
"boost": "1",
"random_score": {},
"boost_mode":"multiply"
}
}
}
}
}
Function Score Query
- Score calculation with multiple filter context query
GET products/_doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"function_score": {
"query": {
"match": {
"child.color": "red"
}
},
"functions": [{
"filter": {
"match": {
"child.lvl1": "men"
}
},
"weight": 2
}, {
"filter": {
"match": {
"child.lvl1": "women"
}
},
"weight": 5
}],
"boost": "1",
"boost_mode":"multiply"
}
}
}
}
}
Function Score Query
-
Score calculation based on script score function
- boost_mode: multiply, replace, sum, avg, max, min
GET products/_doc/_search
{
"query": {
"nested": {
"path": "child",
"query": {
"function_score": {
"query": {
"match": {
"child.color": "red"
}
},
"script_score" : {
"script" : {
"source": "doc['child.price'].value"
}
},
"boost": 0.1,
"boost_mode":"sum"
}
}
}
}
}
Compound Query Boost
-
Score calculation based on script score function
- boost_mode: multiply, replace, sum, avg, max, min
GET products/_doc/_search
{
"query": {
"bool": {
"must": {
"term": {
"name": "jacket"
}
},
"should": [
{
"range": {
"price": {
"lte": 20,
"boost": 0.5
}
}
},
{
"range": {
"price": {
"lte": 15,
"boost": 2
}
}
}
]
}
}
}
Rescore
- Rescoring only the top N documents for precision improving and cost reduction, window_size refers to top N on each shard
POST products/doc/_search
{
"query": {
"nested": {
"type": "child",
"query": {
"match_all": {}
}
}
},
"rescore": {
"window_size" : 500,
"query": {
"rescore_query" : {
"nested": {
"type": "child",
"query": {
"function_score": {
"script_score": {
"script": {
"inline": "doc['price'].value"
}
}
}
}
}
}
}
}
}
Debugging relevancy calculation
- Explain scoring for specific document
- Explain scoring for query
GET /products/_doc/{_id}/_explain
POST products/_doc/_search
{
"explain": true,
"query": {
//......
}
}
- Support manually impact on the order of search result
- Caching on shard
- The results of the entire query are cached here
- Only hits count, aggregation, and suggestions are cached
- The result are only cached if size is 0 and no hits/document
- Query json will be used as cache key
- Default to be 1% of the heap
- Can be configured by indices.requests.cache.size: 1%
Pros and Cons of Query Context
Special processing in common query
- Source fields selection
- Sort
- Pagination
- Highlight
Selecting the fields in the response
- White list in _source
- can use wildcards match "*"
POST products/doc/_search
{
"from": 0,
"size": 24,
"_source": ["pro*"],
"query": {
"nested": {
"path": "child",
"query": {
"term": {
"child.productName": "hat"
}
}
}
}
}
Selecting the fields in the response
- script_fields to format output programatically
POST products/doc/_search
{
"from": 0,
"size": 24,
"_source": [],
"script_fields": {
"max_price_including_unit": {
"script": {
"inline": "'$' + params['_source']['price']"
}
}
},
"query": {
"nested": {
"path": "child",
"query": {
"term": {
"name": "hat"
}
}
}
}
}
Sorting
- Sort
- either by single field or multiple fields
POST products/doc/_search
{
"from": 0,
"size": 24,
"query": {
"nested": {
"path": "child",
"query": {
"term": {
"child.name": "hat"
}
}
}
},
"sort": [{
"child.price": "asc"
}, {
"child.no": "asc"
}]
}
Pagination
- Pagination
- Default page size is 10
POST products/doc/_search
{
"from": 0,
"size": 24,
"query": {
"nested": {
"path": "child",
"query": {
"term": {
"name": "hat"
}
}
}
}
}
Highlighting
POST products/doc/_search
{
"query": {
"nested" : {
"type" : "child",
"score_mode" : "sum",
"query": {
"simple_query_string" : {
"fields" : ["color^2", "size^1"],
"query": "Red"
}
},
"inner_hits": {
"size": 1,
"highlight": {
"fields" : {
"color" : {},
"size" : {},
}
}
}
}
}
}
Thanks
Elasticsearch: Query Basics
By hanyi8000
Elasticsearch: Query Basics
- 2,185