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Extend reading parquet metadata #162

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May 4, 2023
Merged

Extend reading parquet metadata #162

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6f4ae5c
Turn data type of parquet column to Array(String), cast to String whe…
EnricoMi Apr 19, 2023
9235f75
Add null values count to block columns metadata
EnricoMi Apr 19, 2023
eb229e1
Update doc strings and PARQUET.md
EnricoMi Apr 19, 2023
0183962
Remove unused imports
EnricoMi Apr 19, 2023
3b97558
Fix type of column and encodings in PARQUET.md
EnricoMi Apr 19, 2023
c139b8f
Add to CHANGELOG.md
EnricoMi May 4, 2023
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6 changes: 6 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -8,6 +8,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).

- Spark app to diff files or tables and write result back to file or table. (#160)

### Changed

- Added null value count to `parquetBlockColumns` and `parquet_block_columns`. (#162)
- Changed data type of column name in `parquetBlockColumns` and `parquet_block_columns` to array of strings.
Cast to string to get earlier behaviour (string column name). (#162)

## [2.6.0] - 2023-04-11

### Added
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53 changes: 27 additions & 26 deletions PARQUET.md
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Expand Up @@ -109,32 +109,33 @@ spark.read.parquetBlockColumns("/path/to/parquet").show()
spark.read.parquet_block_columns("/path/to/parquet").show()
```
```
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+
| filename|block|column| codec| type| encodings| minValue| maxValue|columnStart|compressedBytes|uncompressedBytes|values|
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+
|file1.parquet| 1| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 0| 99| 4| 437| 826| 100|
|file1.parquet| 1| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.005067503372006343|0.9973357672164814| 441| 831| 826| 100|
|file2.parquet| 1| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 100| 199| 4| 438| 825| 100|
|file2.parquet| 1| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.010617521596503865| 0.999189783846449| 442| 831| 826| 100|
|file2.parquet| 2| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 200| 299| 1273| 440| 826| 100|
|file2.parquet| 2| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.011277044401634018| 0.970525681750662| 1713| 830| 825| 100|
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+
```

|column |type |description |
|:-----------------|:----:|:-----------------------------------------------------|
|filename |string|The Parquet file name |
|block |int |Block / RowGroup number starting at 1 |
|column |string|Block / RowGroup column name |
|codec |string|The coded used to compress the block column values |
|type |string|The data type of the block column |
|encodings |string|Encodings of the block column |
|minValue |string|Minimum value of this column in this block |
|maxValue |string|Maximum value of this column in this block |
|columnStart |long |Start position of the block column in the Parquet file|
|compressedBytes |long |Number of compressed bytes of this block column |
|uncompressedBytes |long |Number of uncompressed bytes of this block column |
|valueCount |long |Number of values in this block column |
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+-----+
| filename|block|column| codec| type| encodings| minValue| maxValue|columnStart|compressedBytes|uncompressedBytes|values|nulls|
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+-----+
|file1.parquet| 1| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 0| 99| 4| 437| 826| 100| 0|
|file1.parquet| 1| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.005067503372006343|0.9973357672164814| 441| 831| 826| 100| 0|
|file2.parquet| 1| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 100| 199| 4| 438| 825| 100| 0|
|file2.parquet| 1| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.010617521596503865| 0.999189783846449| 442| 831| 826| 100| 0|
|file2.parquet| 2| [id]|SNAPPY| required int64 id|[BIT_PACKED, PLAIN]| 200| 299| 1273| 440| 826| 100| 0|
|file2.parquet| 2| [val]|SNAPPY|required double val|[BIT_PACKED, PLAIN]|0.011277044401634018| 0.970525681750662| 1713| 830| 825| 100| 0|
+-------------+-----+------+------+-------------------+-------------------+--------------------+------------------+-----------+---------------+-----------------+------+-----+
```

|column |type |description |
|:-----------------|:-----------:|:-----------------------------------------------------|
|filename |string |The Parquet file name |
|block |int |Block / RowGroup number starting at 1 |
|column |array<string>|Block / RowGroup column name |
|codec |string |The coded used to compress the block column values |
|type |string |The data type of the block column |
|encodings |array<string>|Encodings of the block column |
|minValue |string |Minimum value of this column in this block |
|maxValue |string |Maximum value of this column in this block |
|columnStart |long |Start position of the block column in the Parquet file|
|compressedBytes |long |Number of compressed bytes of this block column |
|uncompressedBytes |long |Number of uncompressed bytes of this block column |
|values |long |Number of values in this block column |
|nulls |long |Number of null values in this block column |

## Parquet partition metadata

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7 changes: 4 additions & 3 deletions python/gresearch/spark/parquet/__init__.py
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Expand Up @@ -72,17 +72,18 @@ def parquet_block_columns(self: DataFrameReader, *paths: str) -> DataFrame:
This provides the following per-block-column information:
- filename (string): The file name
- block (int): Block / RowGroup number starting at 1
- column (string): Block / RowGroup column name
- column (array<string>): Block / RowGroup column name
- codec (string): The coded used to compress the block column values
- type (string): The data type of the block column
- encodings (string): Encodings of the block column
- encodings (array<string>): Encodings of the block column
- minValue (string): Minimum value of this column in this block
- maxValue (string): Maximum value of this column in this block
- columnStart (long): Start position of the block column in the Parquet file
- compressedBytes (long): Number of compressed bytes of this block column
- uncompressedBytes (long): Number of uncompressed bytes of this block column
- values (long): Number of values in this block column

- nulls (long): Number of null values in this block column

:param self: a Spark DataFrameReader
:param paths: paths one or more paths to Parquet files or directories
:return: dataframe with Parquet metadata
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7 changes: 4 additions & 3 deletions src/main/scala/uk/co/gresearch/spark/parquet/package.scala
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Expand Up @@ -22,10 +22,10 @@ import org.apache.hadoop.fs.Path
import org.apache.parquet.hadoop.metadata.BlockMetaData
import org.apache.parquet.hadoop.{Footer, ParquetFileReader}
import org.apache.spark.sql.execution.datasources.FilePartition
import org.apache.spark.sql.functions.spark_partition_id
import org.apache.spark.sql.{DataFrame, DataFrameReader, Encoder, Encoders}

import scala.collection.JavaConverters.collectionAsScalaIterableConverter
import scala.collection.convert.ImplicitConversions.`iterable AsScalaIterable`

package object parquet {
private implicit val intEncoder: Encoder[Int] = Encoders.scalaInt
Expand Down Expand Up @@ -159,7 +159,7 @@ package object parquet {
(
footer.getFile.toString,
idx + 1,
column.getPath.toString,
column.getPath.toSeq,
column.getCodec.toString,
column.getPrimitiveType.toString,
column.getEncodings.asScala.toSeq.map(_.toString).sorted,
Expand All @@ -169,11 +169,12 @@ package object parquet {
column.getTotalSize,
column.getTotalUncompressedSize,
column.getValueCount,
column.getStatistics.getNumNulls,
)
}
}
}
}.toDF("filename", "block", "column", "codec", "type", "encodings", "minValue", "maxValue", "columnStart", "compressedBytes", "uncompressedBytes", "values")
}.toDF("filename", "block", "column", "codec", "type", "encodings", "minValue", "maxValue", "columnStart", "compressedBytes", "uncompressedBytes", "values", "nulls")
}

/**
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19 changes: 11 additions & 8 deletions src/test/scala/uk/co/gresearch/spark/parquet/ParquetSuite.scala
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Expand Up @@ -101,7 +101,7 @@ class ParquetSuite extends AnyFunSuite with SparkTestSession with SparkVersion {
StructType(Seq(
StructField("filename", StringType, nullable = true),
StructField("block", IntegerType, nullable = false),
StructField("column", StringType, nullable = true),
StructField("column", ArrayType(StringType), nullable = true),
StructField("codec", StringType, nullable = true),
StructField("type", StringType, nullable = true),
StructField("encodings", ArrayType(StringType), nullable = true),
Expand All @@ -111,16 +111,19 @@ class ParquetSuite extends AnyFunSuite with SparkTestSession with SparkVersion {
StructField("compressedBytes", LongType, nullable = false),
StructField("uncompressedBytes", LongType, nullable = false),
StructField("values", LongType, nullable = false),
StructField("nulls", LongType, nullable = false),
)),
Seq(
Row("file1.parquet", 1, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "0", "99", 4, 437, 826, 100),
Row("file1.parquet", 1, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.005067503372006343", "0.9973357672164814", 441, 831, 826, 100),
Row("file2.parquet", 1, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "100", "199", 4, 438, 825, 100),
Row("file2.parquet", 1, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.010617521596503865", "0.999189783846449", 442, 831, 826, 100),
Row("file2.parquet", 2, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "200", "299", 1273, 440, 826, 100),
Row("file2.parquet", 2, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.011277044401634018", "0.970525681750662", 1713, 830, 825, 100),
Row("file1.parquet", 1, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "0", "99", 4, 437, 826, 100, 0),
Row("file1.parquet", 1, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.005067503372006343", "0.9973357672164814", 441, 831, 826, 100, 0),
Row("file2.parquet", 1, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "100", "199", 4, 438, 825, 100, 0),
Row("file2.parquet", 1, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.010617521596503865", "0.999189783846449", 442, 831, 826, 100, 0),
Row("file2.parquet", 2, "[id]", "SNAPPY", "required int64 id", "[BIT_PACKED, PLAIN]", "200", "299", 1273, 440, 826, 100, 0),
Row("file2.parquet", 2, "[val]", "SNAPPY", "required double val", "[BIT_PACKED, PLAIN]", "0.011277044401634018", "0.970525681750662", 1713, 830, 825, 100, 0),
),
(df: DataFrame) => df.withColumn("encodings", $"encodings".cast(StringType))
(df: DataFrame) => df
.withColumn("column", $"column".cast(StringType))
.withColumn("encodings", $"encodings".cast(StringType))
)
}

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