Query data in a graph with a parameter

Query data in a Spanner Graph using a parameter.

Code sample

C++

To learn how to install and use the client library for Spanner, see Spanner client libraries.

To authenticate to Spanner, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

void QueryDataWithParameter(google::cloud::spanner::Client client) {
  namespace spanner = ::google::cloud::spanner;

  spanner::SqlStatement select(R"""(
      Graph FinGraph
      MATCH (a:Person)-[o:Owns]->()-[t:Transfers]->()<-[p:Owns]-(b:Person)
      WHERE t.amount >= @min
      RETURN a.name AS sender,
             b.name AS receiver,
             t.amount,
             t.create_time AS transfer_at)""",
                               {{"min", spanner::Value(500)}});
  using RowType =
      std::tuple<std::string, std::string, double, spanner::Timestamp>;
  auto rows = client.ExecuteQuery(std::move(select));
  for (auto& row : spanner::StreamOf<RowType>(rows)) {
    if (!row) throw std::move(row).status();
    std::cout << "sender: " << std::get<0>(*row) << "\t";
    std::cout << "receiver: " << std::get<1>(*row) << "\t";
    std::cout << "amount: " << std::get<2>(*row) << "\t";
    std::cout << "transfer_at: " << std::get<3>(*row) << "\n";
  }

  std::cout
      << "Query completed for [spanner_query_graph_data_with_parameter]\n";
}

Go

To learn how to install and use the client library for Spanner, see Spanner client libraries.

To authenticate to Spanner, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/spanner"
	"google.golang.org/api/iterator"
)

func queryGraphDataWithParameter(w io.Writer, db string) error {
	ctx := context.Background()
	client, err := spanner.NewClient(ctx, db)
	if err != nil {
		return err
	}
	defer client.Close()

	// Execute a Spanner query statement comprising a graph query. Graph queries
	// are characterized by 'MATCH' statements describing node and edge
	// patterns.
	//
	// This statement finds entities ('Account's) owned by all 'Person's 'b' to
	// which transfers greater than a specified 'min' have been made by entities
	// ('Account's) owned by any 'Person' 'a' in the graph called 'FinGraph'.
	// It then returns the names of all such 'Person's 'a' and 'b', and the
	// amount and time of the transfer.
	// The parameter 'min' is distinguished by a leading '@', and the value
	// of the parameter is specified using a map.
	stmt := spanner.Statement{
		SQL: `Graph FinGraph 
			  MATCH (a:Person)-[o:Owns]->()-[t:Transfers]->()<-[p:Owns]-(b:Person)
			  WHERE t.amount >= @min
			  RETURN a.name AS sender, b.name AS receiver, t.amount, t.create_time AS transfer_at`,
		Params: map[string]interface{}{
			"min": 500,
		},
	}
	iter := client.Single().Query(ctx, stmt)
	defer iter.Stop()

	// The results are returned in tabular form. Iterate over the
	// result rows and print them.
	for {
		row, err := iter.Next()
		if err == iterator.Done {
			return nil
		}
		if err != nil {
			return err
		}
		var sender, receiver string
		var amount float64
		var transfer_at time.Time
		if err := row.Columns(&sender, &receiver, &amount, &transfer_at); err != nil {
			return err
		}
		fmt.Fprintf(w, "%s %s %f %s\n", sender, receiver, amount, transfer_at.Format(time.RFC3339))
	}
}

Java

To learn how to install and use the client library for Spanner, see Spanner client libraries.

To authenticate to Spanner, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

static void queryWithParameter(DatabaseClient dbClient) {
  Statement statement =
      Statement.newBuilder(
              "Graph FinGraph MATCH"
                  + " (a:Person)-[o:Owns]->()-[t:Transfers]->()<-[p:Owns]-(b:Person) WHERE"
                  + " t.amount >= @min RETURN a.name AS sender, b.name AS receiver, t.amount,"
                  + " t.create_time AS transfer_at")
          .bind("min")
          .to(500)
          .build();
  try (ResultSet resultSet = dbClient.singleUse().executeQuery(statement)) {
    while (resultSet.next()) {
      System.out.printf(
          "%s %s %f %s\n",
          resultSet.getString("sender"),
          resultSet.getString("receiver"),
          resultSet.getDouble("amount"),
          resultSet.getTimestamp("transfer_at"));
    }
  }
}

Python

To learn how to install and use the client library for Spanner, see Spanner client libraries.

To authenticate to Spanner, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

def query_data_with_parameter(instance_id, database_id):
    """Queries sample data from the database using SQL with a parameter."""

    spanner_client = spanner.Client()
    instance = spanner_client.instance(instance_id)
    database = instance.database(database_id)

    with database.snapshot() as snapshot:
        results = snapshot.execute_sql(
            """Graph FinGraph
            MATCH (a:Person)-[o:Owns]->()-[t:Transfers]->()<-[p:Owns]-(b:Person)
            WHERE t.amount >= @min
            RETURN a.name AS sender, b.name AS receiver, t.amount, t.create_time AS transfer_at""",
            params={"min": 500},
            param_types={"min": spanner.param_types.INT64},
        )

        for row in results:
            print("sender: {}, receiver: {}, amount: {}, transfer_at: {}".format(*row))

What's next

To search and filter code samples for other Google Cloud products, see the Google Cloud sample browser.