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https://issues.apache.org/jira/browse/SPARK-20297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15975559#comment-15975559
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Tim Armstrong commented on SPARK-20297:
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The standard doesn't say that smaller decimals *have* to be stored in
int32/int64, it just is an option for subset of decimal types. int32 and int64
are valid representations for a subset of decimal types. fixed_len_byte_array
and binary are a valid representation of any decimal type.
he int32/int64 options were present in the original version of the decimal
spec, they just weren't widely implemented:
https://github.com/Parquet/parquet-format/commit/b2836e591da8216cfca47075baee2c9a7b0b9289
. So its not a new/old version thing, it was just an alternative
representation that many systems didn't implement.
Not really sure what my point is regarding Spark, but just wanted to leave this
here so future people reading JIRA don't misunderstand what the Parquet spec
says.
> Parquet Decimal(12,2) written by Spark is unreadable by Hive and Impala
> -----------------------------------------------------------------------
>
> Key: SPARK-20297
> URL: https://issues.apache.org/jira/browse/SPARK-20297
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Mostafa Mokhtar
> Labels: integration
>
> While trying to load some data using Spark 2.1 I realized that decimal(12,2)
> columns stored in Parquet written by Spark are not readable by Hive or Impala.
> Repro
> {code}
> CREATE TABLE customer_acctbal(
> c_acctbal decimal(12,2))
> STORED AS Parquet;
> insert into customer_acctbal values (7539.95);
> {code}
> Error from Hive
> {code}
> Failed with exception
> java.io.IOException:parquet.io.ParquetDecodingException: Can not read value
> at 1 in block 0 in file
> hdfs://server1:8020/user/hive/warehouse/tpch_nested_3000_parquet.db/customer_acctbal/part-00000-03d6e3bb-fe5e-4f20-87a4-88dec955dfcd.snappy.parquet
> Time taken: 0.122 seconds
> {code}
> Error from Impala
> {code}
> File
> 'hdfs://server:8020/user/hive/warehouse/tpch_nested_3000_parquet.db/customer_acctbal/part-00000-32db4c61-fe67-4be2-9c16-b55c75c517a4.snappy.parquet'
> has an incompatible Parquet schema for column
> 'tpch_nested_3000_parquet.customer_acctbal.c_acctbal'. Column type:
> DECIMAL(12,2), Parquet schema:
> optional int64 c_acctbal [i:0 d:1 r:0] (1 of 2 similar)
> {code}
> Table info
> {code}
> hive> describe formatted customer_acctbal;
> OK
> # col_name data_type comment
> c_acctbal decimal(12,2)
> # Detailed Table Information
> Database: tpch_nested_3000_parquet
> Owner: mmokhtar
> CreateTime: Mon Apr 10 17:47:24 PDT 2017
> LastAccessTime: UNKNOWN
> Protect Mode: None
> Retention: 0
> Location:
> hdfs://server1.com:8020/user/hive/warehouse/tpch_nested_3000_parquet.db/customer_acctbal
> Table Type: MANAGED_TABLE
> Table Parameters:
> COLUMN_STATS_ACCURATE true
> numFiles 1
> numRows 0
> rawDataSize 0
> totalSize 120
> transient_lastDdlTime 1491871644
> # Storage Information
> SerDe Library:
> org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe
> InputFormat:
> org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat
> OutputFormat:
> org.apache.hadoop.hive.ql.io.parquet.MapredParquetOutputFormat
> Compressed: No
> Num Buckets: -1
> Bucket Columns: []
> Sort Columns: []
> Storage Desc Params:
> serialization.format 1
> Time taken: 0.032 seconds, Fetched: 31 row(s)
> {code}
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