querycoordinator

Documentation

Index

• type Client
• type QueryCoordinator
  • func NewQueryCoordinator(client Client, clients ...Client) *QueryCoordinator
  • func (q *QueryCoordinator) ClientNames() (names []string)
  • func (q *QueryCoordinator) Exec(ctx context.Context, query models.Query, user models.Credentials, ...) map[string]models.QueryResult

Examples

• QueryCoordinator.ClientNames
• QueryCoordinator.Exec

Types

type Client

type Client interface {
	// Name returns unique DSName of the client
	Name() string
	// Exec runs a SQL query against ObjectServer
	Exec(ctx context.Context, query models.Query, user models.Credentials) models.QueryResult
}

type QueryCoordinator

type QueryCoordinator struct {
	// contains filtered or unexported fields
}

QueryCoordinator provides methods to run SQL query against a few ObjectServers concurrently and collect all results

func NewQueryCoordinator

func NewQueryCoordinator(client Client, clients ...Client) *QueryCoordinator

NewQueryCoordinator creates a ready to use instance of coordinator. At least one ObjectServer client must be provided

func (*QueryCoordinator) ClientNames

func (q *QueryCoordinator) ClientNames() (names []string)

ClientNames returns names of all configured clients

Example

client1 := &DemoClient{"ds1", RowSet{}}
client2 := &DemoClient{"ds2", RowSet{}}

coordinator := NewQueryCoordinator(client1, client2)

names := coordinator.ClientNames()

sort.Strings(names)
fmt.Println(names)

Output:

[ds1 ds2]

func (*QueryCoordinator) Exec

func (q *QueryCoordinator) Exec(
	ctx context.Context,
	query models.Query,
	user models.Credentials,
	clientNames ...string,
) map[string]models.QueryResult

Exec runs the given query on the specified NCOS clients and returns the query results for each of them.

If no client names are provided, the query will be executed on all available clients. All unknown client names will be ignored

Example

client1 := &DemoClient{
	DSName: "ds1",
	DBTable: RowSet{
		Columns: []string{"id", "name"},
		Rows:    [][]any{{1, "John"}, {2, "Jane"}},
	},
}

client2 := &DemoClient{
	DSName: "ds2",
	DBTable: RowSet{
		Columns: []string{"id", "name"},
		Rows:    [][]any{{1, "Bob"}},
	},
}

coordinator := NewQueryCoordinator(client1, client2)

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

result := coordinator.Exec(
	ctx,
	Query{SQL: "select * from dbtable"},
	Credentials{UserName: "alice", Password: "secret"},
)

resultJson, _ := json.Marshal(result)
fmt.Println(string(resultJson))

Output:

{"ds1":{"row_set":{"Columns":["id","name"],"Rows":[[1,"John"],[2,"Jane"]]},"affected_rows":0,"error":null},"ds2":{"row_set":{"Columns":["id","name"],"Rows":[[1,"Bob"]]},"affected_rows":0,"error":null}}