升级流程引擎配置文件版本
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// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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package mongo
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import (
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"context"
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"errors"
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"fmt"
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"io"
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"reflect"
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"go.mongodb.org/mongo-driver/bson"
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"go.mongodb.org/mongo-driver/bson/bsoncodec"
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"go.mongodb.org/mongo-driver/x/bsonx"
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"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
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"go.mongodb.org/mongo-driver/x/mongo/driver"
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"go.mongodb.org/mongo-driver/x/mongo/driver/session"
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)
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// Cursor is used to iterate over a stream of documents. Each document can be decoded into a Go type via the Decode
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// method or accessed as raw BSON via the Current field. This type is not goroutine safe and must not be used
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// concurrently by multiple goroutines.
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type Cursor struct {
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// Current contains the BSON bytes of the current change document. This property is only valid until the next call
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// to Next or TryNext. If continued access is required, a copy must be made.
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Current bson.Raw
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bc batchCursor
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batch *bsoncore.DocumentSequence
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batchLength int
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registry *bsoncodec.Registry
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clientSession *session.Client
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err error
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}
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func newCursor(bc batchCursor, registry *bsoncodec.Registry) (*Cursor, error) {
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return newCursorWithSession(bc, registry, nil)
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}
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func newCursorWithSession(bc batchCursor, registry *bsoncodec.Registry, clientSession *session.Client) (*Cursor, error) {
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if registry == nil {
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registry = bson.DefaultRegistry
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}
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if bc == nil {
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return nil, errors.New("batch cursor must not be nil")
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}
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c := &Cursor{
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bc: bc,
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registry: registry,
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clientSession: clientSession,
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}
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if bc.ID() == 0 {
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c.closeImplicitSession()
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}
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// Initialize just the batchLength here so RemainingBatchLength will return an accurate result. The actual batch
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// will be pulled up by the first Next/TryNext call.
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c.batchLength = c.bc.Batch().DocumentCount()
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return c, nil
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}
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func newEmptyCursor() *Cursor {
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return &Cursor{bc: driver.NewEmptyBatchCursor()}
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}
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// NewCursorFromDocuments creates a new Cursor pre-loaded with the provided documents, error and registry. If no registry is provided,
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// bson.DefaultRegistry will be used.
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//
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// The documents parameter must be a slice of documents. The slice may be nil or empty, but all elements must be non-nil.
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func NewCursorFromDocuments(documents []interface{}, err error, registry *bsoncodec.Registry) (*Cursor, error) {
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if registry == nil {
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registry = bson.DefaultRegistry
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}
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// Convert documents slice to a sequence-style byte array.
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var docsBytes []byte
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for _, doc := range documents {
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switch t := doc.(type) {
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case nil:
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return nil, ErrNilDocument
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case bsonx.Doc:
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doc = t.Copy()
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case []byte:
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// Slight optimization so we'll just use MarshalBSON and not go through the codec machinery.
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doc = bson.Raw(t)
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}
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var marshalErr error
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docsBytes, marshalErr = bson.MarshalAppendWithRegistry(registry, docsBytes, doc)
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if marshalErr != nil {
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return nil, marshalErr
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}
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}
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c := &Cursor{
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bc: driver.NewBatchCursorFromDocuments(docsBytes),
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registry: registry,
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err: err,
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}
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// Initialize batch and batchLength here. The underlying batch cursor will be preloaded with the
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// provided contents, and thus already has a batch before calls to Next/TryNext.
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c.batch = c.bc.Batch()
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c.batchLength = c.bc.Batch().DocumentCount()
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return c, nil
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}
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// ID returns the ID of this cursor, or 0 if the cursor has been closed or exhausted.
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func (c *Cursor) ID() int64 { return c.bc.ID() }
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// Next gets the next document for this cursor. It returns true if there were no errors and the cursor has not been
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// exhausted.
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//
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// Next blocks until a document is available, an error occurs, or ctx expires. If ctx expires, the
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// error will be set to ctx.Err(). In an error case, Next will return false.
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//
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// If Next returns false, subsequent calls will also return false.
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func (c *Cursor) Next(ctx context.Context) bool {
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return c.next(ctx, false)
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}
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// TryNext attempts to get the next document for this cursor. It returns true if there were no errors and the next
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// document is available. This is only recommended for use with tailable cursors as a non-blocking alternative to
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// Next. See https://www.mongodb.com/docs/manual/core/tailable-cursors/ for more information about tailable cursors.
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//
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// TryNext returns false if the cursor is exhausted, an error occurs when getting results from the server, the next
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// document is not yet available, or ctx expires. If ctx expires, the error will be set to ctx.Err().
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//
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// If TryNext returns false and an error occurred or the cursor has been exhausted (i.e. c.Err() != nil || c.ID() == 0),
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// subsequent attempts will also return false. Otherwise, it is safe to call TryNext again until a document is
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// available.
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//
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// This method requires driver version >= 1.2.0.
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func (c *Cursor) TryNext(ctx context.Context) bool {
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return c.next(ctx, true)
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}
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func (c *Cursor) next(ctx context.Context, nonBlocking bool) bool {
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// return false right away if the cursor has already errored.
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if c.err != nil {
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return false
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}
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if ctx == nil {
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ctx = context.Background()
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}
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doc, err := c.batch.Next()
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switch err {
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case nil:
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// Consume the next document in the current batch.
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c.batchLength--
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c.Current = bson.Raw(doc)
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return true
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case io.EOF: // Need to do a getMore
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default:
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c.err = err
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return false
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}
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// call the Next method in a loop until at least one document is returned in the next batch or
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// the context times out.
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for {
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// If we don't have a next batch
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if !c.bc.Next(ctx) {
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// Do we have an error? If so we return false.
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c.err = replaceErrors(c.bc.Err())
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if c.err != nil {
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return false
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}
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// Is the cursor ID zero?
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if c.bc.ID() == 0 {
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c.closeImplicitSession()
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return false
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}
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// empty batch, but cursor is still valid.
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// use nonBlocking to determine if we should continue or return control to the caller.
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if nonBlocking {
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return false
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}
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continue
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}
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// close the implicit session if this was the last getMore
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if c.bc.ID() == 0 {
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c.closeImplicitSession()
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}
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// Use the new batch to update the batch and batchLength fields. Consume the first document in the batch.
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c.batch = c.bc.Batch()
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c.batchLength = c.batch.DocumentCount()
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doc, err = c.batch.Next()
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switch err {
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case nil:
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c.batchLength--
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c.Current = bson.Raw(doc)
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return true
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case io.EOF: // Empty batch so we continue
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default:
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c.err = err
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return false
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}
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}
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}
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// Decode will unmarshal the current document into val and return any errors from the unmarshalling process without any
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// modification. If val is nil or is a typed nil, an error will be returned.
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func (c *Cursor) Decode(val interface{}) error {
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return bson.UnmarshalWithRegistry(c.registry, c.Current, val)
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}
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// Err returns the last error seen by the Cursor, or nil if no error has occurred.
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func (c *Cursor) Err() error { return c.err }
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// Close closes this cursor. Next and TryNext must not be called after Close has been called. Close is idempotent. After
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// the first call, any subsequent calls will not change the state.
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func (c *Cursor) Close(ctx context.Context) error {
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defer c.closeImplicitSession()
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return replaceErrors(c.bc.Close(ctx))
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}
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// All iterates the cursor and decodes each document into results. The results parameter must be a pointer to a slice.
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// The slice pointed to by results will be completely overwritten. This method will close the cursor after retrieving
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// all documents. If the cursor has been iterated, any previously iterated documents will not be included in results.
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//
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// This method requires driver version >= 1.1.0.
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func (c *Cursor) All(ctx context.Context, results interface{}) error {
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resultsVal := reflect.ValueOf(results)
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if resultsVal.Kind() != reflect.Ptr {
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return fmt.Errorf("results argument must be a pointer to a slice, but was a %s", resultsVal.Kind())
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}
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sliceVal := resultsVal.Elem()
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if sliceVal.Kind() == reflect.Interface {
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sliceVal = sliceVal.Elem()
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}
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if sliceVal.Kind() != reflect.Slice {
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return fmt.Errorf("results argument must be a pointer to a slice, but was a pointer to %s", sliceVal.Kind())
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}
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elementType := sliceVal.Type().Elem()
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var index int
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var err error
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defer c.Close(ctx)
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batch := c.batch // exhaust the current batch before iterating the batch cursor
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for {
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sliceVal, index, err = c.addFromBatch(sliceVal, elementType, batch, index)
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if err != nil {
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return err
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}
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if !c.bc.Next(ctx) {
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break
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}
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batch = c.bc.Batch()
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}
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if err = replaceErrors(c.bc.Err()); err != nil {
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return err
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}
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resultsVal.Elem().Set(sliceVal.Slice(0, index))
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return nil
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}
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// RemainingBatchLength returns the number of documents left in the current batch. If this returns zero, the subsequent
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// call to Next or TryNext will do a network request to fetch the next batch.
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func (c *Cursor) RemainingBatchLength() int {
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return c.batchLength
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}
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// addFromBatch adds all documents from batch to sliceVal starting at the given index. It returns the new slice value,
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// the next empty index in the slice, and an error if one occurs.
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func (c *Cursor) addFromBatch(sliceVal reflect.Value, elemType reflect.Type, batch *bsoncore.DocumentSequence,
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index int) (reflect.Value, int, error) {
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docs, err := batch.Documents()
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if err != nil {
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return sliceVal, index, err
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}
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for _, doc := range docs {
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if sliceVal.Len() == index {
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// slice is full
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newElem := reflect.New(elemType)
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sliceVal = reflect.Append(sliceVal, newElem.Elem())
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sliceVal = sliceVal.Slice(0, sliceVal.Cap())
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}
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currElem := sliceVal.Index(index).Addr().Interface()
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if err = bson.UnmarshalWithRegistry(c.registry, doc, currElem); err != nil {
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return sliceVal, index, err
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}
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index++
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}
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return sliceVal, index, nil
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}
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func (c *Cursor) closeImplicitSession() {
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if c.clientSession != nil && c.clientSession.SessionType == session.Implicit {
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c.clientSession.EndSession()
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}
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}
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// BatchCursorFromCursor returns a driver.BatchCursor for the given Cursor. If there is no underlying
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// driver.BatchCursor, nil is returned.
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//
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// Deprecated: This is an unstable function because the driver.BatchCursor type exists in the "x" package. Neither this
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// function nor the driver.BatchCursor type should be used by applications and may be changed or removed in any release.
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func BatchCursorFromCursor(c *Cursor) *driver.BatchCursor {
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bc, _ := c.bc.(*driver.BatchCursor)
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return bc
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}
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