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// Copyright 2018-2019 The logrange Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package api
import (
"context"
"fmt"
)
type (
// Querier interface allows to perform read operations.
Querier interface {
// Query runs lql to collect the server data and returns it in the QueryResult.
// It returns an error which indicates that the query could not be delivered to
// the server. If there is no communication problems, but server could not perform
// the query by any reason, the function will return nil, but the server error could
// be found in res.Err
//
// The Query expects res param, where the Query result will be placed (see QueryResult).
// The QueryResult contains the data, which is read and the NextQueryRequest field
// which value may be used for consecutive read requests. Using res.NextQueryRequest allows
// to improve the read performance. Also the res.NextQueryRequest.Pos contains the next
// record read position, which could be used for iterating over the result record collection.
Query(ctx context.Context, req *QueryRequest, res *QueryResult) error
}
// QueryRequest struct describes a request for reading records
QueryRequest struct {
// ReqId identifies the request Id on server side. The field should not be populated by client in
// its first request, but it can be taken from QueryResult.NextQueryRequest for consecutive
// requests.
//
// The field is helpful when records should be read in order by several consecutive reaquests.
// Server could cache some resources to perform the iteration quickly. So the server could return
// a value in QueryResult.NextQueryRequest field, which could be provided with the following request.
ReqId uint64
// Query contains SELECT statement for reading records. This field contains the request, but
// some parameters like POSTION, OFFSET and LIMIT could be overwritten by fields from the QueryResult
Query string
// Pos contains the next read record position. For consecutive batch reading the value
// can be taken from the previous request result QueryResult.NextQueryRequest
Pos string
// WaitTimeout in seconds provide waiting new data timeout in case of the request starts from
// the end of result stream (no records). The timout cannot exceed 60 seconds. When the timeout
// expires and no data is arrived response with no data will be returned.
WaitTimeout int
// Offset contains the offset from the current position (either positive or negative). For
// batch read it should be set to 0 for non-first request.
Offset int
// Limit defines the maximum number of records which could be read from the sources
Limit int
}
// QeryResult struct contains the result returned by the server in a response on LQL execution (see Querier.Query)
QueryResult struct {
// Events slice contains the result of the query execution
Events []*LogEvent
// NextQueryRequest contains the query for reading next porition of events. It makes sense only if Err is
// nil.
NextQueryRequest QueryRequest
// Err the operation error. If the Err is nil, the operation successfully executed
Err error `json:"-"`
}
)
// String is part of Stringify interface
func (qr *QueryRequest) String() string {
return fmt.Sprintf("{ReqId: %d, Query: %s, Pos: %s, WaitTimeout: %d, Offset: %d, Limit: %d}", qr.ReqId, qr.Query, qr.Pos, qr.WaitTimeout, qr.Offset, qr.Limit)
}
// String is part of Stringify interface
func (qres *QueryResult) String() string {
return fmt.Sprintf("{Events: %d, NextQueryReq: %s, Err: %v}", len(qres.Events), qres.NextQueryRequest.String(), qres.Err)
}
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