mirror of https://github.com/minio/minio.git
135 lines
3.4 KiB
Go
135 lines
3.4 KiB
Go
// Copyright (c) 2015-2021 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package json
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import (
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"errors"
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"io"
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"sync"
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"github.com/minio/minio/internal/s3select/sql"
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"github.com/bcicen/jstream"
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)
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// Reader - JSON record reader for S3Select.
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type Reader struct {
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args *ReaderArgs
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decoder *jstream.Decoder
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valueCh chan *jstream.MetaValue
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readCloser io.ReadCloser
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}
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// Read - reads single record.
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func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
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v, ok := <-r.valueCh
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if !ok {
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if err := r.decoder.Err(); err != nil {
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return nil, errJSONParsingError(err)
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}
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return nil, io.EOF
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}
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var kvs jstream.KVS
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if v.ValueType == jstream.Object {
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// This is a JSON object type (that preserves key
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// order)
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kvs = v.Value.(jstream.KVS)
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} else {
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// To be AWS S3 compatible Select for JSON needs to
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// output non-object JSON as single column value
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// i.e. a map with `_1` as key and value as the
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// non-object.
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kvs = jstream.KVS{jstream.KV{Key: "_1", Value: v.Value}}
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}
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dstRec, ok := dst.(*Record)
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if !ok {
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dstRec = &Record{}
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}
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dstRec.KVS = kvs
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dstRec.SelectFormat = sql.SelectFmtJSON
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return dstRec, nil
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}
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// Close - closes underlying reader.
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func (r *Reader) Close() error {
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// Close the input.
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err := r.readCloser.Close()
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for range r.valueCh {
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// Drain values so we don't leak a goroutine.
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// Since we have closed the input, it should fail rather quickly.
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}
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return err
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}
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// NewReader - creates new JSON reader using readCloser.
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func NewReader(readCloser io.ReadCloser, args *ReaderArgs) *Reader {
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readCloser = &syncReadCloser{rc: readCloser}
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d := jstream.NewDecoder(readCloser, 0).ObjectAsKVS()
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return &Reader{
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args: args,
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decoder: d,
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valueCh: d.Stream(),
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readCloser: readCloser,
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}
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}
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// syncReadCloser will wrap a readcloser and make it safe to call Close
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// while reads are running.
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// All read errors are also postponed until Close is called and
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// io.EOF is returned instead.
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type syncReadCloser struct {
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rc io.ReadCloser
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errMu sync.Mutex
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err error
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}
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func (pr *syncReadCloser) Read(p []byte) (n int, err error) {
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// This ensures that Close will block until Read has completed.
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// This allows another goroutine to close the reader.
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pr.errMu.Lock()
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defer pr.errMu.Unlock()
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if pr.err != nil {
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return 0, io.EOF
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}
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n, pr.err = pr.rc.Read(p)
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if pr.err != nil {
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// Translate any error into io.EOF, so we don't crash:
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// https://github.com/bcicen/jstream/blob/master/scanner.go#L48
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return n, io.EOF
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}
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return n, nil
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}
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var errClosed = errors.New("read after close")
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func (pr *syncReadCloser) Close() error {
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pr.errMu.Lock()
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defer pr.errMu.Unlock()
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if pr.err == errClosed {
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return nil
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}
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if pr.err != nil {
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return pr.err
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}
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pr.err = errClosed
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return pr.rc.Close()
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}
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