SEARCH

The SEARCH keyword starts the language construct to filter Views of type ArangoSearch. Conceptually, a View is just another document data source, similar to an array or a document/edge collection, over which you can iterate using a FOR operation in AQL:

FOR doc IN viewName
  RETURN doc

The optional SEARCH operation provides the capabilities to:

  • filter documents based on AQL Boolean expressions and functions
  • match documents located in different collections backed by a fast index
  • sort the result set based on how closely each document matched the search conditions

See ArangoSearch Views on how to set up a View.

Syntax

The SEARCH keyword is followed by an ArangoSearch filter expressions, which is mostly comprised of calls to ArangoSearch AQL functions.

FOR doc IN viewName
  SEARCH expression
  OPTIONS { … }
  ...

Usage

The SEARCH statement, in contrast to FILTER, is treated as a part of the FOR operation, not as an individual statement. It can not be placed freely in a query nor multiple times in the body of a FOR loop. FOR ... IN must be followed by the name of a View, not a collection. The SEARCH operation has to follow next, other operations before SEARCH such as FILTER, COLLECT etc. are not allowed in this position. Subsequent operations are possible after SEARCH and the expression however, including SORT to order the search results based on a ranking value computed by the ArangoSearch View.

expression must be an ArangoSearch expression. The full power of ArangoSearch is harnessed and exposed via special ArangoSearch functions, during both the search and sort stages. On top of that, common AQL operators are supported.

Note that inline expressions and a few other things are not supported by SEARCH. The server will raise a query error in case of an invalid expression.

The OPTIONS keyword and an object can optionally follow the search expression to set Search Options.

Logical operators

Logical or Boolean operators allow you to combine multiple search conditions.

  • AND, && (conjunction)
  • OR, || (disjunction)
  • NOT, ! (negation / inversion)

Operator precedence needs to be taken into account and can be controlled with parentheses.

Consider the following contrived expression:

doc.value < 0 OR doc.value > 5 AND doc.value IN [-10, 10]

AND has a higher precedence than OR. The expression is equivalent to:

doc.value < 0 OR (doc.value > 5 AND doc.value IN [-10, 10])

The conditions are thus:

  • values less than 0
  • values greater than 5, but only if it is 10 (or -10, but this can never be fulfilled)

Parentheses can be used as follows to apply the AND condition to both of the OR conditions:

(doc.value < 0 OR doc.value > 5) AND doc.value IN [-10, 10]

The conditions are now:

  • values less than 0, but only if it is -10
  • values greater than 5, but only if it is 10

Comparison operators

  • == (equal)
  • <= (less than or equal)
  • >= (greater than or equal)
  • < (less than)
  • > (greater than)
  • != (unequal)
  • IN (contained in array or range), also NOT IN
  • LIKE (equal with wildcards, introduced in v3.7.0), also NOT LIKE
FOR doc IN viewName
  SEARCH ANALYZER(doc.text == "quick" OR doc.text == "brown", "text_en")
  // -- or --
  SEARCH ANALYZER(doc.text IN ["quick", "brown"], "text_en")
  RETURN doc

The alphabetical order of characters is not taken into account by ArangoSearch, i.e. range queries in SEARCH operations against Views will not follow the language rules as per the defined Analyzer locale nor the server language (startup option --default-language)! Also see Known Issues.

Array comparison operators

Array comparison operators are supported (introduced in v3.6.0):

LET tokens = TOKENS("some input", "text_en")                 // ["some", "input"]
FOR doc IN myView SEARCH tokens  ALL IN doc.title RETURN doc // dynamic conjunction
FOR doc IN myView SEARCH tokens  ANY IN doc.title RETURN doc // dynamic disjunction
FOR doc IN myView SEARCH tokens NONE IN doc.title RETURN doc // dynamic negation
FOR doc IN myView SEARCH tokens  ALL >  doc.title RETURN doc // dynamic conjunction with comparison
FOR doc IN myView SEARCH tokens  ANY <= doc.title RETURN doc // dynamic disjunction with comparison

Handling of non-indexed fields

Document attributes which are not configured to be indexed by a View are treated by SEARCH as non-existent. This affects tests against the documents emitted from the View only.

For example, given a collection myCol with the following documents:

{ "someAttr": "One", "anotherAttr": "One" }
{ "someAttr": "Two", "anotherAttr": "Two" }

… with a View where someAttr is indexed by the following View myView:

{
  "type": "arangosearch",
  "links": {
    "myCol": {
      "fields": {
        "someAttr": {}
      }
    }
  }
}

… a search on someAttr yields the following result:

FOR doc IN myView
  SEARCH doc.someAttr == "One"
  RETURN doc
[ { "someAttr": "One", "anotherAttr": "One" } ]

A search on anotherAttr yields an empty result because only someAttr is indexed by the View:

FOR doc IN myView
  SEARCH doc.anotherAttr == "One"
  RETURN doc
[]

You can use the special includeAllFields View property to index all (sub-)fields of the source documents if desired.

SEARCH with SORT

The documents emitted from a View can be sorted by attribute values with the standard SORT() operation, using one or multiple attributes, in ascending or descending order (or a mix thereof).

FOR doc IN viewName
  SORT doc.text, doc.value DESC
  RETURN doc

If the (left-most) fields and their sorting directions match up with the primary sort order definition of the View then the SORT operation is optimized away.

Apart from simple sorting, it is possible to sort the matched View documents by relevance score (or a combination of score and attribute values if desired). The document search via the SEARCH keyword and the sorting via the ArangoSearch Scoring Functions, namely BM25() and TFIDF(), are closely intertwined. The query given in the SEARCH expression is not only used to filter documents, but also is used with the scoring functions to decide which document matches the query best. Other documents in the View also affect this decision.

Therefore the ArangoSearch scoring functions can work only on documents emitted from a View, as both the corresponding SEARCH expression and the View itself are consulted in order to sort the results.

FOR doc IN viewName
  SEARCH ...
  SORT BM25(doc) DESC
  RETURN doc

The BOOST() function can be used to fine-tune the resulting ranking by weighing sub-expressions in SEARCH differently.

If there is no SEARCH operation prior to calls to scoring functions or if the search expression does not filter out documents (e.g. SEARCH true) then a score of 0 will be returned for all documents.

Search Options

The SEARCH operation accepts an options object with the following attributes:

  • collections (array, optional): array of strings with collection names to restrict the search to certain source collections
  • conditionOptimization (string, optional): controls how search criteria get optimized (introduced in v3.6.2). Possible values:
    • "auto" (default): convert conditions to disjunctive normal form (DNF) and apply optimizations. Removes redundant or overlapping conditions, but can take quite some time even for a low number of nested conditions.
    • "none": search the index without optimizing the conditions.

Examples

Given a View with three linked collections coll1, coll2 and coll3 it is possible to return documents from the first two collections only and ignore the third using the collections option:

FOR doc IN viewName
  SEARCH true OPTIONS { collections: ["coll1", "coll2"] }
  RETURN doc

The search expression true matches all View documents. You can use any valid expression here while limiting the scope to the chosen source collections.