53 lines
1.3 KiB
Go
53 lines
1.3 KiB
Go
package sqlitex
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import (
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"context"
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"runtime"
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"github.com/go-llsqlite/crawshaw"
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)
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// GetSnapshot returns a Snapshot that should remain available for reads until
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// it is garbage collected.
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//
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// This sets aside a Conn from the Pool with an open read transaction until the
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// Snapshot is garbage collected or the Pool is closed. Thus, until the
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// returned Snapshot is garbage collected, the Pool will have one fewer Conn,
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// and it should not be possible for the WAL to be checkpointed beyond the
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// point of the Snapshot.
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//
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// See sqlite.Conn.GetSnapshot and sqlite.Snapshot for more details.
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func (p *Pool) GetSnapshot(ctx context.Context, schema string) (*sqlite.Snapshot, error) {
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conn := p.Get(ctx)
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if conn == nil {
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return nil, context.Canceled
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}
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conn.SetInterrupt(nil)
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s, release, err := conn.GetSnapshot(schema)
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if err != nil {
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return nil, err
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}
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snapshotGCd := make(chan struct{})
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runtime.SetFinalizer(s, nil)
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runtime.SetFinalizer(s, func(s *sqlite.Snapshot) {
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// Free the C resources associated with the Snapshot.
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s.Free()
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close(snapshotGCd)
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})
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go func() {
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select {
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case <-p.closed:
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case <-snapshotGCd:
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}
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// Allow the WAL to be checkpointed past the point of
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// the Snapshot.
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release()
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// Return the conn to the Pool for reuse.
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p.Put(conn)
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}()
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return s, nil
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}
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