If the text search generates no results, the regex query will not be executed.
A regex query combined with a logical and will only traverse the text search query's superset. This is too broad, but it is already a subset of the desired result. A simple search against a text index returns all documents with indexed text that contain the words we are looking for. For example, if the regex expression is example, then this query will only look for strings that begin with example. Create a query that uses regular expression as a prefix expression and requires all matches to begin with a specific string character. When compared to traditional regular expression scanning, this speeds up search and data retrieval from the collection. We can create database indexes on the document fields so that the MongoDB query can use the indexed values to match the regular expression. Some of the concepts used in MongoDB for query optimization are as follows: We can optimise MongoDB regular expression queries in the same way that we do in relational database queries. The $options with 'I' parameter (case insensitivity) specifies that we want to run the search regardless of whether we find the letters 'Gu' in lower or upper case. But it is still showing us all the documents, this is the power of $options. In the above query, we search for ‘ish’ in the employeename irrespective of its case. 
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If you want to use Perl compatible regular expressions that are not supported by JavaScript, you must use the $regex operator. They do not effectively use index for case-insensitive regular expression queries. Rather than scanning all of the collections, this is the quickest way to find a match. If the index of the specified field is available for case-sensitive regular expression queries, MongoDB matches the regular expression to the values in the index. Starting with the latest version of MongoDB, you can use the $not operator in combination with the $regex operator expression. If you want to use the x and s options, you must use the $regex operator expression in conjunction with $options. If you want to include a regular expression within a comma-separated list of query conditions, use the $regex operator. You are not permitted to use the $regex operator within the $in operator. Step 1: Create a database “regx” and collection “employee” using MongoDB compass. Let’s see how we can add these documents in our database.įor this tutorial, you need to have MongoDB and MongoDB Compass installed on your system. The following example demonstrates how this can be accomplished. It is useful when we do not know the exact field value for which we are searching in the document.Īssume we have the Employee collection with the Field names "employeeid" and "employeename". Assume we also have the following documents in our collection. In MongoDB, the regex operator is used to search for specific strings in a collection. Using $regex operator for Pattern matching Pattern matching without the $regex operator. Using $regex operator for Pattern matching. We can do pattern matching in MongoDB in two ways: MONGODB COMPASS FILTER OR CONDITION FULL
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This is where regular expressions can help in the retrieval of data based on pattern matching search values.Ī regular expression is a generalised method for matching patterns with character sequences. When retrieving documents from a collection, you may not always know what Field value to look for.
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