Run projection query
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Run a projection query.
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For detailed documentation that includes this code sample, see the following:
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[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],[],[[["\u003cp\u003eThis content demonstrates how to run a projection query in Datastore mode across multiple programming languages including C#, Go, Java, Node.js, PHP, Python, and Ruby.\u003c/p\u003e\n"],["\u003cp\u003eThe code samples focus on extracting specific properties, "priority" and "percent_complete", from entities in the Datastore.\u003c/p\u003e\n"],["\u003cp\u003eTo interact with Datastore, you'll need to utilize the respective Datastore mode client libraries for each language, and you can find instructions in the documentation.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication is required to access Datastore mode, and setting up Application Default Credentials is the suggested method for local development.\u003c/p\u003e\n"],["\u003cp\u003eThe Google Cloud sample browser is recommended for finding code examples for other Google Cloud services.\u003c/p\u003e\n"]]],[],null,["# Run projection query\n\nRun a projection query.\n\nExplore further\n---------------\n\n\nFor detailed documentation that includes this code sample, see the following:\n\n- [Datastore queries](/datastore/docs/concepts/queries)\n\nCode sample\n-----------\n\n### C#\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode C# API\nreference documentation](https://cloud.google.com/dotnet/docs/reference/Google.Cloud.Datastore.V1/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n Query query = new Query(\"Task\")\n {\n Projection = { \"priority\", \"percent_complete\" }\n };\n List\u003clong\u003e priorities = new List\u003clong\u003e();\n List\u003cdouble\u003e percentCompletes = new List\u003cdouble\u003e();\n foreach (var entity in _db.RunQuery(query).Entities)\n {\n priorities.Add((long)entity[\"priority\"]);\n percentCompletes.Add((double)entity[\"percent_complete\"]);\n }\n\n### Go\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Go API\nreference documentation](https://cloud.google.com/go/docs/reference/cloud.google.com/go/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n var priorities []int\n var percents []float64\n it := client.Run(ctx, query)\n for {\n \tvar task Task\n \tif _, err := it.Next(&task); err == iterator.Done {\n \t\tbreak\n \t} else if err != nil {\n \t\tlog.Fatal(err)\n \t}\n \tpriorities = append(priorities, task.Priority)\n \tpercents = append(percents, task.PercentComplete)\n }\n\n### Java\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Java API\nreference documentation](https://cloud.google.com/java/docs/reference/google-cloud-datastore/latest/history).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n List\u003cLong\u003e priorities = new LinkedList\u003c\u003e();\n List\u003cDouble\u003e percentCompletes = new LinkedList\u003c\u003e();\n QueryResults\u003cProjectionEntity\u003e tasks = datastore.run(query);\n while (tasks.hasNext()) {\n ProjectionEntity task = tasks.next();\n priorities.add(task.getLong(\"priority\"));\n percentCompletes.add(task.getDouble(\"percent_complete\"));\n }\n\n### Node.js\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Node.js API\nreference documentation](https://cloud.google.com/nodejs/docs/reference/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n async function runProjectionQuery() {\n const priorities = [];\n const percentCompletes = [];\n const [tasks] = await datastore.runQuery(query);\n tasks.forEach(task =\u003e {\n priorities.push(task.priority);\n percentCompletes.push(task.percent_complete);\n });\n\n return {\n priorities: priorities,\n percentCompletes: percentCompletes,\n };\n }\n\n### PHP\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode PHP API\nreference documentation](https://googleapis.github.io/google-cloud-php/#/docs/cloud-datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n $priorities = array();\n $percentCompletes = array();\n $result = $datastore-\u003erunQuery($query);\n /* @var Entity $task */\n foreach ($result as $task) {\n $priorities[] = $task['priority'];\n $percentCompletes[] = $task['percent_complete'];\n }\n\n### Python\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Python API\nreference documentation](https://cloud.google.com/python/docs/reference/datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n priorities = []\n percent_completes = []\n\n for task in query.fetch():\n priorities.append(task[\"priority\"])\n percent_completes.append(task[\"percent_complete\"])\n\n### Ruby\n\n\nTo learn how to install and use the client library for Datastore mode, see\n[Datastore mode client libraries](/datastore/docs/reference/libraries).\n\n\nFor more information, see the\n[Datastore mode Ruby API\nreference documentation](/ruby/docs/reference/google-cloud-datastore/latest).\n\n\nTo authenticate to Datastore mode, set up Application Default Credentials.\nFor more information, see\n\n[Set up authentication for a local development environment](/docs/authentication/set-up-adc-local-dev-environment).\n\n priorities = []\n percent_completes = []\n datastore.run(query).each do |task|\n priorities \u003c\u003c task[\"priority\"]\n percent_completes \u003c\u003c task[\"percent_complete\"]\n end\n\nWhat's next\n-----------\n\n\nTo search and filter code samples for other Google Cloud products, see the\n[Google Cloud sample browser](/docs/samples?product=datastore)."]]
