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This PR attempts to introduce
Decimal
again. This time changes include:Decimal
inbasic.rs
alongside ByteArray and Int96. Since decimal can be created fromi32
,i64
orByteArray
, we have enum with 3 variations of underlying storage (either array of clone of ByteArray).num-bigint
because of that.As it was previously noted, Parquet-cpp/mr, Arrow explicitly support decimal as int128 value. Spark uses Java BigDecimal, which supports arbitrary precision values, but Spark itself limits Decimal to precision 38, which is int128.
We do not store decimal as a value, but rather 3 parts: unscaled value as bytes, precision and scale, which is different from Spark, for example, where they try storing it as long. When converting to a string we use
num-bigint
, which, similar to JavaBigDecimal
, should support arbitrary precision.