s3select should honour custom record delimiter (#6419)
Allow custom delimiters like `\r\n`, `a`, `\r` etc in input csv and replace with `\n`. Fixes #6403master
Praveen raj Mani
6 years ago
committed by
Nitish Tiwari
parent
92bc7caf7a
commit
30d4a2cf53
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/* |
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* Minio Cloud Storage, (C) 2018 Minio, Inc. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package ioutil |
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import ( |
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"bufio" |
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"io" |
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) |
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var ( |
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nByte byte = 10 // the byte that corresponds to the '\n' rune.
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rByte byte = 13 // the byte that corresponds to the '\r' rune.
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) |
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// DelimitedReader reduces the custom delimiter to `\n`.
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type DelimitedReader struct { |
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r *bufio.Reader |
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delimiter []rune // Select can have upto 2 characters as delimiter.
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assignEmpty bool // Decides whether the next read byte should be discarded.
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} |
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// NewDelimitedReader detects the custom delimiter and replaces with `\n`.
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func NewDelimitedReader(r io.Reader, delimiter []rune) *DelimitedReader { |
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return &DelimitedReader{r: bufio.NewReader(r), delimiter: delimiter, assignEmpty: false} |
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} |
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// Reads and replaces the custom delimiter with `\n`.
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func (r *DelimitedReader) Read(p []byte) (n int, err error) { |
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n, err = r.r.Read(p) |
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if err != nil { |
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return |
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} |
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for i, b := range p { |
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if r.assignEmpty { |
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swapAndNullify(p, i) |
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r.assignEmpty = false |
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continue |
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} |
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if b == rByte && rune(b) != r.delimiter[0] { |
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// Replace the carriage returns with `\n`.
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// Mac styled csv will have `\r` as their record delimiter.
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p[i] = nByte |
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} else if rune(b) == r.delimiter[0] { // Eg, `\r\n`,`ab`,`a` are valid delimiters
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if i+1 == len(p) && len(r.delimiter) > 1 { |
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// If the first delimiter match falls on the boundary,
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// Peek the next byte and if it matches, discard it in the next byte read.
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if nextByte, nerr := r.r.Peek(1); nerr == nil { |
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if rune(nextByte[0]) == r.delimiter[1] { |
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p[i] = nByte |
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// To Discard in the next read.
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r.assignEmpty = true |
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} |
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} |
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} else if len(r.delimiter) > 1 && rune(p[i+1]) == r.delimiter[1] { |
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// The second delimiter falls in the same chunk.
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p[i] = nByte |
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r.assignEmpty = true |
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} else if len(r.delimiter) == 1 { |
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// Replace with `\n` incase of single charecter delimiter match.
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p[i] = nByte |
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} |
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} |
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} |
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return |
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} |
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// Occupy the first byte space and nullify the last byte.
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func swapAndNullify(p []byte, n int) { |
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for i := n; i < len(p)-1; i++ { |
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p[i] = p[i+1] |
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} |
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p[len(p)-1] = 0 |
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} |
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@ -0,0 +1,83 @@ |
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/* |
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* Minio Cloud Storage, (C) 2016, 2017, 2018 Minio, Inc. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package ioutil |
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import ( |
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"bytes" |
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"io" |
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"strings" |
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"testing" |
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) |
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// Test for DelimitedCSVReader.
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func TestDelimitedReader(t *testing.T) { |
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expected := "username,age\nbanana,12\ncarrot,23\napple,34\nbrinjal,90\nraddish,45" |
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inputs := []struct { |
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inputcsv string |
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delimiter string |
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chunkSize int |
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}{ |
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// case 1 - with default `\n` delimiter.
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{"username,age\nbanana,12\ncarrot,23\napple,34\nbrinjal,90\nraddish,45", "\n", 10}, |
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// case 2 - with carriage return `\r` which should be replaced with `\n` by default.
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{"username,age\rbanana,12\rcarrot,23\rapple,34\rbrinjal,90\rraddish,45", "\n", 10}, |
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// case 3 - with a double character delimiter (octals).
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{"username,age\r\nbanana,12\r\ncarrot,23\r\napple,34\r\nbrinjal,90\r\nraddish,45", "\r\n", 10}, |
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// case 4 - with a double character delimiter.
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{"username,agexvbanana,12xvcarrot,23xvapple,34xvbrinjal,90xvraddish,45", "xv", 10}, |
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// case 5 - with a double character delimiter `\t `
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{"username,age\t banana,12\t carrot,23\t apple,34\t brinjal,90\t raddish,45", "\t ", 10}, |
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// case 6 - This is a special case where the first delimiter match falls in the 13'th byte space
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// ie, the last byte space of the read chunk, In this case the reader should peek in the next byte
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// and replace with `\n`.
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{"username,agexxbanana,12xxcarrot,23xxapple,34xxbrinjal,90xxraddish,45", "xx", 13}, |
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} |
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for c, input := range inputs { |
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var readcsv []byte |
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var err error |
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delimitedReader := NewDelimitedReader(strings.NewReader(input.inputcsv), []rune(input.delimiter)) |
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for err == nil { |
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chunk := make([]byte, input.chunkSize) |
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_, err = delimitedReader.Read(chunk) |
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readcsv = append(readcsv, chunk...) |
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} |
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if err != io.EOF { |
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t.Fatalf("Case %d: Error in delimited read", c+1) |
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} |
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expected := []byte(expected) |
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cleanCsv := removeNulls(readcsv) |
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if !bytes.Equal(cleanCsv, expected) { |
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t.Fatalf("Case %d: Expected the delimited csv to be `%s`, but instead found `%s`", c+1, string(expected), string(cleanCsv)) |
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} |
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} |
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} |
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// Removes all the tailing nulls in chunks.
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// Null chunks will be assigned if there is a reduction
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// Eg, When `xv` is reduced to `\n`, the last byte is nullified.
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func removeNulls(csv []byte) []byte { |
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cleanCsv := []byte{} |
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for _, p := range csv { |
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if p != 0 { |
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cleanCsv = append(cleanCsv, p) |
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} |
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} |
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return cleanCsv |
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} |
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