[T1] Allow fixed length encoding for min/max and deprecate encoding_stats #252
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src/main/thrift/parquet.thrift
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| * Only one pair of max_value/min_value, max1/min1, max2/min2, max4/min4, | ||
| * max8/min8 can be set. The pair is determined by the physical type of the | ||
| * column. Floating point values are bitcasted to integers. Variable length | ||
| * values are set in min_value/max_value. |
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Could you please update the docs for readers for backwards compatibility should check min_value/max_value if the non-variable width field is not not set?
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Rewritten this to be clearer.
| */ | ||
| 5: optional binary max_value; | ||
| 6: optional binary min_value; | ||
| /** If true, max_value is the actual maximum value for a column */ | ||
| 7: optional bool is_max_value_exact; | ||
| /** If true, min_value is the actual minimum value for a column */ | ||
| 8: optional bool is_min_value_exact; | ||
| 9: optional i64 max8; |
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did you intentionally elide min1/max1? (they are still mentioned above).
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Yes I removed them because they provide little benefit and do not justify the added complexity. This is because in thrift these are ulebs so it makes no difference in the wire. For flatbuffers this would make a difference though.
| @@ -810,9 +803,13 @@ struct ColumnMetaData { | |||
| /** optional statistics for this column chunk */ | |||
| 12: optional Statistics statistics; | |||
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| /** Set of all encodings used for pages in this column chunk. | |||
| /** | |||
| * DEPRECATED: use is_fully_dict_encoded instead | |||
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I would suggest making this a separate PR, I think we'd prefer to keep the changes as small and focused as possible?
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Agreed. I will create another PR for the Statistics change alone if we are OK merging that now.
…tats 1. Add `min8`/`max8` fields for encoding fixed length binary encoding for min/max for physical types less than or equal 8 bytes. 2. Deprecate `ColumnMetaData.encoding_stats` and replace with a bool `ColumnMetaData.is_fully_dict_encoded`
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| * the columns ColumnOrder | ||
| * max_value/min_value: PLAIN encoded values, sans length prefix if varlen | ||
| * max8/min8: up to 8-bytes: | ||
| * FLOAT, DOUBLE: bitcasted to INT32 and INT64, respectively |
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I think we might want to be more specific here about values less then 8 bytes are translated into 8 bytes. In practice it doesn't make a difference for readers but it would be good to limit ambiguity. I assume we do a normal cast from 1/4 integer byte values to 8 bytes values rather then just embedding them?
min8/max8fields for encoding fixed length binary encoding for min/max for physical types less than or equal 8 bytes.ColumnMetaData.encoding_statsand replace with a boolColumnMetaData.is_fully_dict_encoded'ref Parquet Metadata evolution
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