176 lines
5.1 KiB
Plaintext
176 lines
5.1 KiB
Plaintext
[[search-request-track-total-hits]]
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=== Track total hits
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Generally the total hit count can't be computed accurately without visiting all
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matches, which is costly for queries that match lots of documents. The
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`track_total_hits` parameter allows you to control how the total number of hits
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should be tracked. When set to `true` the search response will always track the
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number of hits that match the query accurately (e.g. `total.relation` will always
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be equal to `"eq"` when `track_total_hits is set to true).
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[source,js]
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--------------------------------------------------
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GET twitter/_search
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{
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"track_total_hits": true,
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"query": {
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"match" : {
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"message" : "Elasticsearch"
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}
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}
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}
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--------------------------------------------------
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// TEST[setup:twitter]
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// CONSOLE
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\... returns:
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[source,js]
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--------------------------------------------------
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{
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"_shards": ...
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"timed_out": false,
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"took": 100,
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"hits": {
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"max_score": 1.0,
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"total" : {
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"value": 2048, <1>
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"relation": "eq" <2>
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},
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"hits": ...
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}
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}
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--------------------------------------------------
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// TESTRESPONSE[s/"_shards": \.\.\./"_shards": "$body._shards",/]
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// TESTRESPONSE[s/"took": 100/"took": $body.took/]
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// TESTRESPONSE[s/"max_score": 1\.0/"max_score": $body.hits.max_score/]
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// TESTRESPONSE[s/"value": 2048/"value": $body.hits.total.value/]
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// TESTRESPONSE[s/"hits": \.\.\./"hits": "$body.hits.hits"/]
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<1> The total number of hits that match the query.
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<2> The count is accurate (e.g. `"eq"` means equals).
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If you don't need to track the total number of hits you can improve query times
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by setting this option to `false`. In such case the search can efficiently skip
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non-competitive hits because it doesn't need to count all matches:
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[source,js]
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--------------------------------------------------
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GET twitter/_search
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{
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"track_total_hits": false,
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"query": {
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"match" : {
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"message" : "Elasticsearch"
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[continued]
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\... returns:
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[source,js]
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--------------------------------------------------
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{
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"_shards": ...
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"timed_out": false,
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"took": 10,
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"hits" : { <1>
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"max_score": 1.0,
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"hits": ...
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}
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}
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--------------------------------------------------
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// TESTRESPONSE[s/"_shards": \.\.\./"_shards": "$body._shards",/]
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// TESTRESPONSE[s/"took": 10/"took": $body.took/]
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// TESTRESPONSE[s/"max_score": 1\.0/"max_score": $body.hits.max_score/]
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// TESTRESPONSE[s/"hits": \.\.\./"hits": "$body.hits.hits"/]
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<1> The total number of hits is unknown.
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Given that it is often enough to have a lower bound of the number of hits,
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such as "there are at least 1000 hits", it is also possible to set
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`track_total_hits` as an integer that represents the number of hits to count
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accurately. The search can efficiently skip non-competitive document as soon
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as collecting at least $`track_total_hits` documents. This is a good trade
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off to speed up searches if you don't need the accurate number of hits after
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a certain threshold.
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For instance the following query will track the total hit count that match
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the query accurately up to 100 documents:
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[source,js]
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--------------------------------------------------
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GET twitter/_search
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{
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"track_total_hits": 100,
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"query": {
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"match" : {
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"message" : "Elasticsearch"
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[continued]
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The `hits.total.relation` in the response will indicate if the
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value returned in `hits.total.value` is accurate (`eq`) or a lower
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bound of the total (`gte`).
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For instance the following response:
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[source,js]
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--------------------------------------------------
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{
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"_shards": ...
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"timed_out": false,
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"took": 30,
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"hits" : {
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"max_score": 1.0,
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"total" : {
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"value": 42, <1>
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"relation": "eq" <2>
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},
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"hits": ...
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}
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}
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--------------------------------------------------
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// TESTRESPONSE[s/"_shards": \.\.\./"_shards": "$body._shards",/]
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// TESTRESPONSE[s/"took": 30/"took": $body.took/]
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// TESTRESPONSE[s/"max_score": 1\.0/"max_score": $body.hits.max_score/]
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// TESTRESPONSE[s/"value": 42/"value": $body.hits.total.value/]
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// TESTRESPONSE[s/"hits": \.\.\./"hits": "$body.hits.hits"/]
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<1> 42 documents match the query
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<2> and the count is accurate (`"eq"`)
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\... indicates that the number of hits returned in the `total`
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is accurate.
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If the total number of his that match the query is greater than the
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value set in `track_total_hits`, the total hits in the response
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will indicate that the returned value is a lower bound:
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[source,js]
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--------------------------------------------------
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{
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"_shards": ...
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"hits" : {
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"max_score": 1.0,
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"total" : {
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"value": 100, <1>
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"relation": "gte" <2>
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},
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"hits": ...
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}
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}
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--------------------------------------------------
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// TESTRESPONSE
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// TEST[skip:response is already tested in the previous snippet]
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<1> There are at least 100 documents that match the query
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<2> This is a lower bound (`gte`). |