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Term suggester

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Term suggester

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Added in 0.90.0.Beta1.

In order to understand the format of suggestions, please read the Suggesters page first.

The term suggester suggests terms based on edit distance. The provided suggest text is analyzed before terms are suggested. The suggested terms are provided per analyzed suggest text token. The term suggester doesn’t take the query into account that is part of request.

Common suggest options:

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`text`	The suggest text. The suggest text is a required option that needs to be set globally or per suggestion.
`field`	The field to fetch the candidate suggestions from. This is an required option that either needs to be set globally or per suggestion.
`analyzer`	The analyzer to analyse the suggest text with. Defaults to the search analyzer of the suggest field.
`size`	The maximum corrections to be returned per suggest text token.
`sort`	Defines how suggestions should be sorted per suggest text term. Two possible values: `score`: Sort by sore first, then document frequency and then the term itself. `frequency`: Sort by document frequency first, then similarity score and then the term itself.
`suggest_mode`	The suggest mode controls what suggestions are included or controls for what suggest text terms, suggestions should be suggested. Three possible values can be specified: `missing`: Only suggest terms in the suggest text that aren’t in the index. This is the default. `popular`: Only suggest suggestions that occur in more docs then the original suggest text term. `always`: Suggest any matching suggestions based on terms in the suggest text.

Other term suggest options:

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`lowercase_terms`	Lower cases the suggest text terms after text analysis.
`max_edits`	The maximum edit distance candidate suggestions can have in order to be considered as a suggestion. Can only be a value between 1 and 2. Any other value result in an bad request error being thrown. Defaults to 2.
`prefix_len`	The number of minimal prefix characters that must match in order be a candidate suggestions. Defaults to 1. Increasing this number improves spellcheck performance. Usually misspellings don’t occur in the beginning of terms.
`min_word_len`	The minimum length a suggest text term must have in order to be included. Defaults to 4.
`shard_size`	Sets the maximum number of suggestions to be retrieved from each individual shard. During the reduce phase only the top N suggestions are returned based on the `size` option. Defaults to the `size` option. Setting this to a value higher than the `size` can be useful in order to get a more accurate document frequency for spelling corrections at the cost of performance. Due to the fact that terms are partitioned amongst shards, the shard level document frequencies of spelling corrections may not be precise. Increasing this will make these document frequencies more precise.
`max_inspections`	A factor that is used to multiply with the `shards_size` in order to inspect more candidate spell corrections on the shard level. Can improve accuracy at the cost of performance. Defaults to 5.
`min_doc_freq`	The minimal threshold in number of documents a suggestion should appear in. This can be specified as an absolute number or as a relative percentage of number of documents. This can improve quality by only suggesting high frequency terms. Defaults to 0f and is not enabled. If a value higher than 1 is specified then the number cannot be fractional. The shard level document frequencies are used for this option.
`max_term_freq`	The maximum threshold in number of documents a suggest text token can exist in order to be included. Can be a relative percentage number (e.g 0.4) or an absolute number to represent document frequencies. If an value higher than 1 is specified then fractional can not be specified. Defaults to 0.01f. This can be used to exclude high frequency terms from being spellchecked. High frequency terms are usually spelled correctly on top of this also improves the spellcheck performance. The shard level document frequencies are used for this option.

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