How to Implement Case-Insensitive Sorting with Cloud Firestore\'s Query?

Firestore Case-Insensitive Sorting with Cloud Firestore's Query

In Cloud Firestore, data sorting is inherently case-sensitive. Utilizing the OrderBy method sorts data in ascending or descending order based on the specified field. However, if data contains variations in case, such as 'AAA' and 'aaa', the returned order may not be as desired.

The Issue with Case-Sensitive Sorting

By default, Firestore sorts data in the following order:

AAA
BBB
aaa
bbb

However, the expectation might be:

AAA
aaa
BBB
bbb

Solution: Storing Case-Insensitive Data

Since Firestore does not provide a built-in flag to ignore case during sorting, the only way to achieve case-insensitive sorting is to store an additional field that contains a case-insensitive version of the data.

Consider a field called myData that stores values 'AAA' and 'aaa'. To make sorting case-insensitive, you need to store a second field called myData_insensitive with the case-insensitive version of the data:

DocA:
-> myData = 'AAA'
-> myData_insensitive = 'AAA'

DocB:
-> myData = 'aaa'
-> myData_insensitive = 'AAA'

DocC:
-> myData = 'BBB'
-> myData_insensitive = 'BBB'

DocD:
-> myData = 'bbb'
-> myData_insensitive = 'BBB'

Querying and Ordering by Case-Insensitive Data

You can now query and order data by myData_insensitive, which will provide the desired case-insensitive sorting result.

Unicode and Local Considerations

It's important to note that case normalization for Unicode is more complex than simply converting to lowercase or uppercase. Languages may have different collation rules, affecting how characters are sorted.

Using Case Folding for Case Normalization

To address these complexities, you can implement case normalization using case folding, which ensures that characters with different case forms (e.g., 'a', 'A') are treated as equivalent. Modern browsers support native functions for this.

Here's an example:

<code class="javascript">caseFoldNormalize = function (s) {
  return s.normalize('NFKC').toLowerCase().toUpperCase().toLowerCase();
};</code>

This example converts the string s to the fully normalized version, ignoring case differences.

By utilizing case-insensitive sorting and normalization, you can effectively sort data in Cloud Firestore in a case-insensitive manner, ensuring consistency in data ordering regardless of case variations.

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