Matching Exact Values with ArangoSearch
Search for exact strings, numbers or number ranges, as well as booleans without Analyzer transformations applied
If you want to find strictly equal values, then the identity
Analyzer is what
you need. It will not apply any transformations. It is a no-operation Analyzer
that passes everything through unaltered.
Matching an Exact String
You can index and search strings with the identity
Analyzer for exact
matching, that is case-sensitive, with accented characters as-is, and only if
the entire string is equal (not matching substrings).
Dataset: IMDB movie dataset
View definition:
{
"links": {
"imdb_vertices": {
"fields": {
"title": {
"analyzers": [
"identity"
]
}
}
}
}
}
AQL queries:
Match exact movie title (case-sensitive, full string):
FOR doc IN imdb
SEARCH ANALYZER(doc.title == "The Matrix", "identity")
RETURN doc.title
Result |
---|
The Matrix |
It is not necessary to set the Analyzer context with the ANALYZER()
function
here, because the default Analyzer is identity
anyway. The following query
will return the exact same results:
FOR doc IN imdb
SEARCH doc.title == "The Matrix"
RETURN doc.title
However, being explicit about the Analyzer context helps with clarity and it
also makes it easier to adjust queries if you want to use something other than
the identity
Analyzers. A common pitfall is to index a field with a certain
Analyzer, but forgetting to set this Analyzer as context in the query.
The consequence is usually an empty result, because there is nothing in the
View index for the implicitly requested Analyzer. Or the field happens to be
indexed with the identity
Analyzer as well, but there are no or different
matches because of different Analyzer pre-processing between the indexed data
and the search terms.
Matching Multiple Strings
You can search for several alternatives by combining multiple conditions with
logical OR
s, but you can also use the IN
operator for the same purpose.
The advantage of the IN
operator is that it scales better with the number of
alternatives and allows you to use a single query for a varying amount of
strings that you want to match.
Match multiple exact movie titles using OR
:
FOR doc IN imdb
SEARCH ANALYZER(doc.title == "The Matrix" OR doc.title == "The Matrix Reloaded", "identity")
RETURN doc.title
Result |
---|
The Matrix |
The Matrix Reloaded |
Match multiple exact movie titles using IN
:
FOR doc IN imdb
SEARCH ANALYZER(doc.title IN ["The Matrix", "The Matrix Reloaded"], "identity")
RETURN doc.title
Result |
---|
The Matrix |
The Matrix Reloaded |
By substituting the array of strings with a bind parameter, it becomes possible to use the same query for an arbitrary amount of alternative strings to match:
FOR doc IN imdb
SEARCH ANALYZER(doc.title IN @titles, "identity")
RETURN doc.title
Bind parameters:
{
"titles": [
"The Matrix",
"The Matrix Reloaded",
"The Matrix Revolutions",
"The Matrix Trilogy",
"The Matrix Revisited"
]
}
Result |
---|
The Matrix Revisited |
The Matrix |
The Matrix Reloaded |
The Matrix Revolutions |
The Matrix Trilogy |
Using Negations
Searching for exact values does not end with one or many equality conditions,
but extends to negations as well. You can search for inequality with the !=
operator to return everything from the View index but documents that do not
fulfill the criterion. This is also works with multiple alternatives using the
NOT IN
operator.
Match movies that do not have the title The Matrix
:
FOR doc IN imdb
SEARCH ANALYZER(doc.title != "The Matrix", "identity")
RETURN doc.title
Result |
---|
… |
null |
null |
“Ploning” |
null |
“Code Rush” |
null |
null |
null |
null |
“Ghost in the Shell 2.0” |
“Christmas in Wonderland” |
null |
… |
Note that this includes documents that do not even have a title attribute,
with the effect of returning many null
values in the result.
Match movies that neither have the title The Matrix
nor The Matrix Reloaded
.
Post-filter the results to exclude implicit null
s:
FOR doc IN imdb
SEARCH ANALYZER(doc.title NOT IN ["The Matrix", "The Matrix Reloaded"], "identity")
FILTER doc.title != null
RETURN doc.title
Result |
---|
Ploning |
Code Rush |
Ghost in the Shell 2.0 |
Christmas in Wonderland |
Hadashi no Gen |
The Magician |
… |
A better way to ignore documents without title attribute is to change the View
property storeValues
(not to be confused with storedValues
!) from "none"
to "id"
. You can then use the EXISTS()
function
to test whether there is a title field or not. On a single server with this
particular dataset, the query is roughly five times faster than the previous
one without EXISTS()
:
FOR doc IN imdb
SEARCH ANALYZER(EXISTS(doc.title) AND doc.title NOT IN ["The Matrix", "The Matrix Reloaded"], "identity")
RETURN doc.title
Result |
---|
Ploning |
Code Rush |
Ghost in the Shell 2.0 |
Christmas in Wonderland |
Hadashi no Gen |
The Magician |
… |