Lettura con un filtro
Mantieni tutto organizzato con le raccolte
Salva e classifica i contenuti in base alle tue preferenze.
Leggi il valore più recente in una determinata colonna utilizzando un filtro.
Per saperne di più
Per la documentazione dettagliata che include questo esempio di codice, vedi quanto segue:
Esempio di codice
Salvo quando diversamente specificato, i contenuti di questa pagina sono concessi in base alla licenza Creative Commons Attribution 4.0, mentre gli esempi di codice sono concessi in base alla licenza Apache 2.0. Per ulteriori dettagli, consulta le norme del sito di Google Developers. Java è un marchio registrato di Oracle e/o delle sue consociate.
[[["Facile da capire","easyToUnderstand","thumb-up"],["Il problema è stato risolto","solvedMyProblem","thumb-up"],["Altra","otherUp","thumb-up"]],[["Difficile da capire","hardToUnderstand","thumb-down"],["Informazioni o codice di esempio errati","incorrectInformationOrSampleCode","thumb-down"],["Mancano le informazioni o gli esempi di cui ho bisogno","missingTheInformationSamplesINeed","thumb-down"],["Problema di traduzione","translationIssue","thumb-down"],["Altra","otherDown","thumb-down"]],[],[[["\u003cp\u003eThis page demonstrates how to read the most recent value in a specific column of a Bigtable table using a filter.\u003c/p\u003e\n"],["\u003cp\u003eCode examples are provided in C++, C#, Java, Node.js, PHP, Python, and Ruby, each showing how to retrieve a single row based on a filter.\u003c/p\u003e\n"],["\u003cp\u003eThe examples showcase how to use the respective Bigtable client libraries for each language and set up Application Default Credentials for authentication.\u003c/p\u003e\n"],["\u003cp\u003eUsers can find additional code samples for Bigtable and other Google Cloud products through the Google Cloud sample browser.\u003c/p\u003e\n"]]],[],null,["Read the most recent value in a given column using a filter.\n\nExplore further\n\n\nFor detailed documentation that includes this code sample, see the following:\n\n- [C# hello world](/bigtable/docs/samples-c-sharp-hello)\n- [C++ hello world](/bigtable/docs/samples-cpp-hello)\n- [Node.js hello world](/bigtable/docs/samples-nodejs-hello)\n- [PHP hello world](/bigtable/docs/samples-php-hello)\n- [Python hello world](/bigtable/docs/samples-python-hello)\n- [Ruby hello world](/bigtable/docs/samples-ruby-hello)\n\nCode sample \n\nC++\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 StatusOr\u003cstd::pair\u003cbool, cbt::Row\u003e\u003e result = table.ReadRow(\"key-0\", filter);\n if (!result) throw std::move(result).status();\n if (!result-\u003efirst) {\n std::cout \u003c\u003c \"Cannot find row 'key-0' in the table: \" \u003c\u003c table.table_name()\n \u003c\u003c \"\\n\";\n return;\n }\n cbt::Cell const& cell = result-\u003esecond.cells().front();\n std::cout \u003c\u003c cell.family_name() \u003c\u003c \":\" \u003c\u003c cell.column_qualifier() \u003c\u003c \" @ \"\n \u003c\u003c cell.timestamp().count() \u003c\u003c \"us\\n\"\n \u003c\u003c '\"' \u003c\u003c cell.value() \u003c\u003c '\"' \u003c\u003c \"\\n\";\n\nC#\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 // Read from the table.\n Console.WriteLine(\"Read the first row\");\n\n int rowIndex = 0;\n\n // Read a specific row. Apply a filter to return latest only cell value accross entire row.\n Row rowRead = bigtableClient.ReadRow(\n tableName, rowKey: rowKeyPrefix + rowIndex, filter: filter);\n Console.WriteLine(\n $\"\\tRow key: {rowRead.Key.ToStringUtf8()} \" +\n $\" -- Value: {rowRead.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} \" +\n $\" -- Time Stamp: {rowRead.Families[0].Columns[0].Cells[0].TimestampMicros}\");\n\nJava\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 private void readRowFilter(String tableId, Filter filter) {\n String rowKey =\n Base64.getEncoder().encodeToString(\"greeting0\".getBytes(StandardCharsets.UTF_8));\n Row row = dataClient.readRow(TableId.of(tableId), rowKey, filter);\n printRow(row);\n System.out.println(\"Row filter completed.\");\n }\n\nNode.js\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 console.log('Reading a single row by row key');\n const [singleRow] = await table.row('greeting0').get({filter});\n console.log(`\\tRead: ${getRowGreeting(singleRow)}`);\n\nPHP\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 printf('Getting a single greeting by row key.' . PHP_EOL);\n $key = 'greeting0';\n // Only retrieve the most recent version of the cell.\n $rowFilter = (new RowFilter())-\u003esetCellsPerColumnLimitFilter(1);\n\n $column = 'greeting';\n $columnFamilyId = 'cf1';\n\n $row = $table-\u003ereadRow($key, [\n 'filter' =\u003e $rowFilter\n ]);\n printf('%s' . PHP_EOL, $row[$columnFamilyId][$column][0]['value']);\n\nPython\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 print(\"Getting a single greeting by row key.\")\n key = \"greeting0\".encode()\n\n row = table.read_row(key, row_filter)\n cell = row.cells[column_family_id][column][0]\n print(cell.value.decode(\"utf-8\"))\n\nRuby\n\n\nTo learn how to install and use the client library for Bigtable, see\n[Bigtable client libraries](/bigtable/docs/reference/libraries).\n\n\nTo authenticate to Bigtable, 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 puts \"Reading a single row by row key\"\n row = table.read_row \"greeting0\", filter: filter\n puts \"Row key: #{row.key}, Value: #{row.cells[column_family].first.value}\"\n\nWhat's next\n\n\nTo search and filter code samples for other Google Cloud products, see the\n[Google Cloud sample browser](/docs/samples?product=bigtable)."]]