What is Wildcard in mongoDB

[Ajay_Moladiya]

what is wildcard in mongoDB ? Give me details of wildcard index or search with example…

[Kushagra_Kesav]

Hi @Ajay_Moladiya,

Welcome to the MongoDB Community forums

The wildcard operator enables queries that use special characters in the search string that can match any character.

Character	Description
?	Matches any single character.
*	Matches 0 or more characters.
\	Escape character.

To learn more about wildcard operators, please refer to this link

wildcard — MongoDB Atlas

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Wildcard indexing is an index that can filter and automatically matches any field, sub-document, or array in a collection and then index those matches.

Consider an application that captures product data under the productMetadata field and supports querying against that data:

{ "productMetadata": { "category": "electronics", "brand": "Apple" } } 
{ "productMetadata": { "category": "clothing", "brand": "Nike" } } 
{ "productMetadata": { "category" : "electronics", "manufacturer": "Sony" } } 
{ "productMetadata": "out of stock" }

Now, the user wants to create indexes to support queries on any subfield of productMetadata. A wildcard index on productMetadata can support single-field queries on productMetadata, productMetadata.category, productMetadata.brand, and productMetadata.manufacturer:

db.products.createIndex( { "productMetadata.$**" : 1 } )

The index can support the following queries:

db.products.find({ "productMetadata.category" : "electronics" })
db.products.find({ "productMetadata.brand" : "Nike" })
db.products.find({ "productMetadata.manufacturer" : "Sony" })
db.products.find({ "productMetadata" : "out of stock" })

In all of these queries, the index on productMetadata.$** would be used to speed up the query. The $** wildcard specifier matches all subfields of the productMetadata field, so the index can be used to satisfy any query that involves productMetadata.

To learn more, please refer to this link:

Wildcard Indexes — MongoDB Manual

I hope it helps. Let us know if you have any further questions.

Regards,
Kushagra