Advanced Reading and Writing Samples

This example is for advanced reading and writing operations on bigtable data client, that illustrates how to:

  • Use ReadModifyWrite to append a string to a value.
  • Use ReadModifyWrite to increment a value.
  • Use the features to simplify reading big-endian values from Cloud Bigtable.
  • Use CheckAndMutate to modify a value only if it exists.

Run the example

This example uses the Cloud Bigtable C++ Client Library to communicate with Cloud Bigtable.

To run the example program, follow the instructions for the example on GitHub.

Include the Necessary Headers

The example uses the following headers:

#include "google/cloud/bigtable/table.h"

Connect to the Cloud Bigtable data client endpoint.

 google::cloud::bigtable::Table table( google::cloud::bigtable::MakeDataConnection(), google::cloud::bigtable::TableResource(project_id, instance_id, table_id));

Use ReadModifyWrite to increment a value and append a string to a value.

 namespace cbt = ::google::cloud::bigtable; using ::google::cloud::StatusOr; [](cbt::Table table, std::string const& row_key) { StatusOr<cbt::Row> row = table.ReadModifyWriteRow( row_key, cbt::ReadModifyWriteRule::IncrementAmount("fam", "counter", 1), cbt::ReadModifyWriteRule::AppendValue("fam", "list", ";element")); // As the modify in this example is not idempotent, and this example // does not attempt to retry if there is a failure, we simply print // such failures, if any, and otherwise ignore them. if (!row) { std::cout << "Failed to append row: " << row.status().message() << "\n"; return; } // Print the contents of the row std::cout << row->row_key() << "\n"; for (auto const& cell : row->cells()) { std::cout << " " << cell.family_name() << ":" << cell.column_qualifier() << " = <"; if (cell.column_qualifier() == "counter") { // This example uses "counter" to store 64-bit numbers in big-endian // format, extract them as follows: std::cout << cell.decode_big_endian_integer<std::int64_t>().value(); } else { std::cout << cell.value(); } std::cout << ">\n"; } }

Use the features to simplify reading big-endian values from Cloud Bigtable.

 namespace cbt = ::google::cloud::bigtable; using ::google::cloud::StatusOr; [](google::cloud::bigtable::Table table, std::string const& row_key) { StatusOr<std::pair<bool, cbt::Row>> tuple = table.ReadRow( row_key, cbt::Filter::ColumnName("stats_summary", "os_build")); if (!tuple) throw std::move(tuple).status(); if (!tuple->first) { std::cout << "Row " << row_key << " not found\n"; return; } PrintRow(tuple->second); }

Use CheckAndMutate to modify a cell if it has a value.

 namespace cbt = ::google::cloud::bigtable; using ::google::cloud::StatusOr; [](cbt::Table table, std::string const& row_key) { // Check if the latest value of the flip-flop column is "on". cbt::Filter predicate = cbt::Filter::Chain( cbt::Filter::ColumnRangeClosed("fam", "flip-flop", "flip-flop"), cbt::Filter::Latest(1), cbt::Filter::ValueRegex("on")); // If the predicate matches, change the latest value to "off", otherwise, // change the latest value to "on". Modify the "flop-flip" column at the // same time. StatusOr<cbt::MutationBranch> branch = table.CheckAndMutateRow(row_key, std::move(predicate), {cbt::SetCell("fam", "flip-flop", "off"), cbt::SetCell("fam", "flop-flip", "on")}, {cbt::SetCell("fam", "flip-flop", "on"), cbt::SetCell("fam", "flop-flip", "off")}); if (!branch) throw std::move(branch).status(); if (*branch == cbt::MutationBranch::kPredicateMatched) { std::cout << "The predicate was matched\n"; } else { std::cout << "The predicate was not matched\n"; } }

Use CheckAndMutate to modify a cell if another cell exists.

 namespace cbt = ::google::cloud::bigtable; using ::google::cloud::StatusOr; [](cbt::Table table, std::string const& row_key) { // Check if the latest value of the "test-column" column is present, // regardless of its value. cbt::Filter predicate = cbt::Filter::Chain( cbt::Filter::ColumnRangeClosed("fam", "test-column", "test-column"), cbt::Filter::Latest(1)); // If the predicate matches, do nothing, otherwise set the // "had-test-column" to "false": StatusOr<cbt::MutationBranch> branch = table.CheckAndMutateRow( row_key, std::move(predicate), {}, {cbt::SetCell("fam", "had-test-column", "false")}); if (!branch) throw std::move(branch).status(); if (*branch == cbt::MutationBranch::kPredicateMatched) { std::cout << "The predicate was matched\n"; } else { std::cout << "The predicate was not matched\n"; } }