[GitHub] [incubator-iceberg] aokolnychyi commented on issue #131: Fix collection of bounds for small decimals in ParquetMetrics

[GitBox <gi...@apache.org>]

aokolnychyi commented on issue #131: Fix collection of bounds for small decimals in ParquetMetrics
URL: https://github.com/apache/incubator-iceberg/pull/131#issuecomment-473393292
 
 
   @rdblue Let's assume we have `3.50` as Decimal(10, 2), which is represented as INT64 in Parquet.
   
   ```
   file schema: table 
   --------------------------------------------------------------------------------
   decimalCol:  OPTIONAL INT64 O:DECIMAL R:0 D:1
   
   row group 1: RC:1 TS:75 OFFSET:4 
   --------------------------------------------------------------------------------
   decimalCol:   INT64 GZIP DO:0 FPO:4 SZ:91/75/0.82 VC:1 ENC:BIT_PACKED,PLAIN,RLE ST:[min: 3.50, max: 3.50, num_nulls: 0]
   ```
   
   Once we read the footer and call `stats.genericGetMin()` for this decimal column, we will get `350`. This value must be properly scaled (handled by `converterFromParquet`) before creating a literal.
   
   Right now, `Literals.of((Long) 350).to(DecimalType.of(10, 2)` will give us `350.00` instead of `3.50`.

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