The following examples use a collection called products with the following documents. The $regex implementation, for example, is not collation-aware and hence cannot use case-insensitive indexes. Regular expression queries that are case insensitive can’t leverage indexes efficiently. After matching the prefix, /^a/ can stop searching. If a suitable index exists, all of these expressions use it nevertheless, /^a.*/ and /^a.*$/ are slower. For example, the regex /^abc.*/ will be optimized by only matching against index values that begin with abc.įurthermore, while /^a/, /^a.*/, and /^a.*$/ all match comparable strings, their performance is different. If a regular expression begins with a caret ( ^) or a left anchor ( \A), followed by a string of simple symbols, it is called a prefix expression. ![]() ![]() This enables MongoDB to create a range from the prefix and only match against index values within that range. More optimization is possible if the regular expression has a prefix expression, which indicates that all potential matches begin with the exact string. Use MongoDB Compass: MongoDB's free visualization tool is great for getting a quick. If the field has an index, MongoDB checks the regular expression against the values in the index, which can be faster than a collection scan for case-sensitive regular expression queries. Use regular expressions: Again, since indexes are ordered by value. pattern/) but not with the $regex operator expressions. In version 4.0.6 and earlier, you could use the $not operator with regular expression objects (i.e. Consider the following example.ĭb.inventory.find ( ) Only JavaScript regular expression objects (i.e., /pattern/) can be used to incorporate a regular expression in the $in query expression. The $regex operator doesn’t support the global search modifier g. ) to match any character, including newlines. It will require $regex with $options syntax s It allows the dot character (. The x option does not affect how the VT character is handled (i.e., code 11). ![]() White space characters might not appear within special character sequences in a pattern this only pertains to data characters. It also ignores characters in the middle and includes an unescaped hash/pound ( #) character and the following newline, allowing you to add comments in complex patterns. x All white space characters in the $regex pattern are ignored unless they are escaped or included in a character class. The m option has no effect if the pattern has no anchors or if the string value contains no newline characters (e.g. m For strings with multi-line values, match at the beginning or end of each line for patterns that include anchors such as ^ at the start and $ at the end. Option Description Syntax Restrictions i Case insensitive to match upper and lower cases. The user can use regular expressions with the following.
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