Consulta datos en un gráfico con un parámetro

Consultar datos en un grafo de Spanner mediante un parámetro.

Muestra de código

C++

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Para autenticarte en Spanner, configura las credenciales predeterminadas de la aplicación. Si deseas obtener más información, consulta Configura la autenticación para un entorno de desarrollo local.

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

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Para autenticarte en Spanner, configura las credenciales predeterminadas de la aplicación. Si deseas obtener más información, consulta Configura la autenticación para un entorno de desarrollo local.

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

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Para autenticarte en Spanner, configura las credenciales predeterminadas de la aplicación. Si deseas obtener más información, consulta Configura la autenticación para un entorno de desarrollo local.

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

Para obtener información sobre cómo instalar y usar la biblioteca cliente de Spanner, consulta Bibliotecas cliente de Spanner.

Para autenticarte en Spanner, configura las credenciales predeterminadas de la aplicación. Si deseas obtener más información, consulta Configura la autenticación para un entorno de desarrollo local.

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))

¿Qué sigue?

Para buscar y filtrar muestras de código para otros productos de Google Cloud, consulta el navegador de muestra de Google Cloud.