Cosmos DB - 删除文档

Question

如何从 Cosmos DB 中删除单个记录？

我可以使用 SQL 语法进行选择：

SELECT *
FROM collection1
WHERE (collection1._ts > 0)

确实返回了所有文档（类似于行？）

但是当我尝试删除时这不起作用

DELETE
FROM collection1
WHERE (collection1._ts > 0)

我如何做到这一点？

Answer 1

DocumentDB API 的 SQL 专门用于查询。也就是说，它只提供SELECT，而不提供UPDATE或DELETE。

完全支持这些操作，但需要调用 REST（或 SDK）。例如，对于 .net，您将调用 DeleteDocumentAsync() 或 ReplaceDocumentAsync()，而在 node.js 中，这将是对 deleteDocument() 或 replaceDocument() 的调用。

在您的特定场景中，您可以运行 SELECT 来识别要删除的文档，然后进行“删除”调用，每个文档一个（或者，为了提高效率和事务性，将要删除的文档数组传递到存储的程序）。

Answer 2

最简单的方法可能是使用Azure Storage Explorer。连接后，您可以深入选择一个容器，选择一个文档，然后将其删除。您可以在 https://gotcosmos.com/tools 上找到适用于 Cosmos DB 的其他工具。

Answer 3

另一个需要考虑的选项是生存时间 (TTL)。您可以为集合打开此功能，然后为文档设置过期时间。文件过期后会自动为您清理。

Answer 4

使用以下代码创建一个存储过程：

/**
 * A Cosmos DB stored procedure that bulk deletes documents for a given query.
 * Note: You may need to execute this stored procedure multiple times (depending whether the stored procedure is able to delete every document within the execution timeout limit).
 *
 * @function
 * @param {string} query - A query that provides the documents to be deleted (e.g. "SELECT c._self FROM c WHERE c.founded_year = 2008"). Note: For best performance, reduce the # of properties returned per document in the query to only what's required (e.g. prefer SELECT c._self over SELECT * )
 * @returns {Object.<number, boolean>} Returns an object with the two properties:
 *   deleted - contains a count of documents deleted
 *   continuation - a boolean whether you should execute the stored procedure again (true if there are more documents to delete; false otherwise).
 */
function bulkDeleteStoredProcedure(query) {
    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();
        }
    }
}

并使用您的分区键（例如：null）和查询以选择文档（例如：SELECT c._self FROM c 删除所有）来执行它。

基于Delete Documents from CosmosDB based on condition through Query Explorer

Answer 5

这是一个如何使用 .net Cosmos SDK V3 使用 bulkDeleteStoredProcedure 的示例。

由于执行边界，必须使用ContinuationFlag。

private async Task<int> ExecuteSpBulkDelete(string query, string partitionKey)
    {
        var continuationFlag = true;
        var totalDeleted = 0;
        while (continuationFlag)
        {
            StoredProcedureExecuteResponse<BulkDeleteResponse> result = await _container.Scripts.ExecuteStoredProcedureAsync<BulkDeleteResponse>(
                "spBulkDelete", // your sproc name
                new PartitionKey(partitionKey), // pk value
                new[] { sql });

            var response = result.Resource;
            continuationFlag = response.Continuation;
            var deleted = response.Deleted;
            totalDeleted += deleted;
            Console.WriteLine($"Deleted {deleted} documents ({totalDeleted} total, more: {continuationFlag}, used {result.RequestCharge}RUs)");
        }

        return totalDeleted;
    }

和响应模型：

public class BulkDeleteResponse
{
    [JsonProperty("deleted")]
    public int Deleted { get; set; }

    [JsonProperty("continuation")]
    public bool Continuation { get; set; }
}