Recently we were required to do bulk delete of data that exists on Cosmos DB. This was required as a one time process for the purpose of cleaning orphaned data that has been caused due to legacy functionality from another system.
To provide an overview of the current structure for recording data onto Cosmos DB is setup as shown below. In our instance the partition_key is the car_color
Unfortunately, Cosmos DB doesn't provide functionality out of the box to accommodate this requirement. To accomplish this task, one can make use of the following stored procedure. This needs to be added to the container where the data needs to be deleted.
var collection = getContext().getCollection();
var collectionLink = collection.getSelfLink();
var response = getContext().getResponse();
var responseBody = {
deleted: 0,
continuation: true
};
// Validate input.
if (!query) throw new Error("The query is undefined or null.");
tryQueryAndDelete();
// Recursively runs the query w/ support for continuation tokens.
// Calls tryDelete(documents) as soon as the query returns documents.
function tryQueryAndDelete(continuation) {
var requestOptions = {continuation: continuation};
var isAccepted = collection.queryDocuments(collectionLink, query, requestOptions, function (err, retrievedDocs, responseOptions) {
if (err) throw err;
if (retrievedDocs.length > 0) {
// Begin deleting documents as soon as documents are returned form the query results.
// tryDelete() resumes querying after deleting; no need to page through continuation tokens.
// - this is to prioritize writes over reads given timeout constraints.
tryDelete(retrievedDocs);
} else if (responseOptions.continuation) {
// Else if the query came back empty, but with a continuation token; repeat the query w/ the token.
tryQueryAndDelete(responseOptions.continuation);
} else {
// Else if there are no more documents and no continuation token - we are finished deleting documents.
responseBody.continuation = false;
response.setBody(responseBody);
}
});
// If we hit execution bounds - return continuation: true.
if (!isAccepted) {
response.setBody(responseBody);
}
}
// Recursively deletes documents passed in as an array argument.
// Attempts to query for more on empty array.
function tryDelete(documents) {
if (documents.length > 0) {
// Delete the first document in the array.
var isAccepted = collection.deleteDocument(documents[0]._self, {}, function (err, responseOptions) {
if (err) throw err;
responseBody.deleted++;
documents.shift();
// Delete the next document in the array.
tryDelete(documents);
});
// If we hit execution bounds - return continuation: true.
if (!isAccepted) {
response.setBody(responseBody);
}
} else {
// If the document array is empty, query for more documents.
tryQueryAndDelete();
}
}
}
When executing this stored procedure apart from the query parameter, one needs to also include the partition_key. Hence the data that would be deleted would only be within a specific partition and not on the whole container. Should the user require to delete data from different partitions, the stored procedure needs to be executed multiple times by supplying each time the related partition_key.
