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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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.
//go:build go1.18
package pqarrow
import (
"context"
"github.com/apache/arrow-go/v18/arrow"
"github.com/apache/arrow-go/v18/arrow/array"
"github.com/apache/arrow-go/v18/arrow/compute"
"github.com/apache/arrow-go/v18/arrow/memory"
"github.com/apache/arrow-go/v18/parquet"
"github.com/apache/arrow-go/v18/parquet/file"
"github.com/apache/arrow-go/v18/parquet/internal/debug"
"github.com/apache/arrow-go/v18/parquet/internal/encoding"
)
func isDictEncoding(enc parquet.Encoding) bool {
return enc == parquet.Encodings.PlainDict
}
func dictionaryDirectWriteSupported(arr arrow.Array) bool {
debug.Assert(arr.DataType().ID() == arrow.DICTIONARY, "should only be called with dictionary type")
dt := arr.DataType().(*arrow.DictionaryType)
return arrow.IsPrimitive(dt.ValueType.ID()) || arrow.IsBaseBinary(dt.ValueType.ID())
}
func convertDictionaryToDense(mem memory.Allocator, arr arrow.Array) (arrow.Array, error) {
dt := arr.DataType().(*arrow.DictionaryType).ValueType
ctx := compute.WithAllocator(context.Background(), mem)
return compute.CastArray(ctx, arr, compute.SafeCastOptions(dt))
}
func writeDictionaryArrow(ctx *arrowWriteContext, cw file.ColumnChunkWriter, leafArr arrow.Array, defLevels, repLevels []int16, maybeParentNulls bool) (err error) {
// if this is the first time writing a dictionary array,
// then there's a few possible paths to take:
//
// - If dictionary encoding is not enabled, just convert to densely
// encoded and call writeDenseArrow
// - Dictionary Encoding is enabled:
// - If this is the first time this is called, then we
// call PutDictionary into the encoder and PutIndices on each
// chunk. We store the dictionary that was written so that
// subsequent calls to this method can make sure the dictionary
// hasn't changed.
// - on subsequent calls, we have to check whether the dictionary
// has changed. If it has, then we trigger the varying dictionary
// path and materialize each chunk and call writeDenseArrow with that
writeDense := func() error {
denseArr, err := convertDictionaryToDense(ctx.props.mem, leafArr)
if err != nil {
return err
}
defer denseArr.Release()
return writeDenseArrow(ctx, cw, denseArr, defLevels, repLevels, maybeParentNulls)
}
if !isDictEncoding(cw.CurrentEncoder().Encoding()) || !dictionaryDirectWriteSupported(leafArr) {
// no longer dictionary-encoding for whatever reason, maybe we never were
// or we decided to stop. Note that writeArrowToColumn can be invoked multiple
// times with both dense and dictionary-encoded versions of the same data
// without a problem. Any dense data will be hashed to indices until the
// dictionary page limit is reached, at which everything (dict and dense)
// will fall back to plain encoding
return writeDense()
}
var (
dictEncoder = cw.CurrentEncoder().(encoding.DictEncoder)
data = leafArr.(*array.Dictionary)
dict = data.Dictionary()
indices = data.Indices()
preserved = dictEncoder.PreservedDictionary()
pageStats = cw.PageStatistics()
)
updateStats := func() error {
var referencedDict arrow.Array
ctx := compute.WithAllocator(context.Background(), ctx.props.mem)
// if dictionary is the same dictionary we already have, just use that
if preserved != nil && preserved == dict {
referencedDict = preserved
} else {
referencedIndices, err := compute.UniqueArray(ctx, indices)
if err != nil {
return err
}
// on first run, we might be able to re-use the existing dict
if referencedIndices.Len() == dict.Len() {
referencedDict = dict
} else {
referencedDict, err = compute.TakeArrayOpts(ctx, dict, referencedIndices, compute.TakeOptions{BoundsCheck: false})
if err != nil {
return err
}
defer referencedDict.Release()
}
referencedIndices.Release()
}
nonNullCount := indices.Len() - indices.NullN()
pageStats.IncNulls(int64(len(defLevels) - nonNullCount))
pageStats.IncNumValues(int64(nonNullCount))
return pageStats.UpdateFromArrow(referencedDict, false)
}
switch {
case preserved == nil:
if err := dictEncoder.PutDictionary(dict); err != nil {
return err
}
// if there were duplicate values in the dictionary, the encoder's
// memo table will be out of sync with the indices in the arrow array
// the easiest solution for this uncommon case is to fallback to plain
// encoding
if dictEncoder.NumEntries() != dict.Len() {
cw.FallbackToPlain()
return writeDense()
}
if pageStats != nil {
if err := updateStats(); err != nil {
return err
}
}
case !array.Equal(dict, preserved):
// dictionary has changed
cw.FallbackToPlain()
return writeDense()
default:
// dictionary is the same but we need to update stats
if pageStats != nil {
if err := updateStats(); err != nil {
return err
}
}
}
return cw.WriteDictIndices(indices, defLevels, repLevels)
}
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