[GitHub] [arrow-rs] crepererum edited a comment on issue #264: Include NaN in Parquet stats (again)

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

crepererum edited a comment on issue #264:
URL: https://github.com/apache/arrow-rs/issues/264#issuecomment-833629444


   # Prior Art
   
   ## PostgreSQL
   > In most implementations of the “not-a-number” concept, NaN is not considered equal to any other numeric value (including NaN). In order to allow numeric values to be sorted and used in tree-based indexes, PostgreSQL treats NaN values as equal, and greater than all non-NaN values.
   
   https://www.postgresql.org/docs/13/datatype-numeric.html
   
   **=> Follows this proposal**
   
   ## CockroachDB
   Follows PostgreSQL, see https://github.com/cockroachdb/cockroach/issues/18860
   
   **=> Follows this proposal**
   
   ## Oracle
   > The floating-point value NaN is greater than any other numeric value and is equal to itself.
   
   https://docs.oracle.com/database/121/TTSQL/types.htm#TTSQL165
   
   **=> Follows this proposal**
   
   ## Snowflake
   > Comparison semantics for `'NaN'` differ from the IEEE 754 standard in the following ways:
   >
   > Condition | Snowflake | IEEE 754 | Comment
   > -- | -- | -- | --
   > `'NaN' = 'NaN'` | `TRUE` | `FALSE` | In Snowflake, `'NaN'` values are all equal.
   > `'NaN' > X`  where `X` is any FLOAT value, including  infinity (other than `NaN` itself). | `TRUE` | `FALSE` | Snowflake treats `'NaN'` as greater  than any other FLOAT value,  including infinity.
   
   
   https://docs.snowflake.com/en/sql-reference/data-types-numeric.html#float-float4-float8
   
   **=> Follows this proposal**
   
   ## Vertica
   > Vertica follows the IEEE definition of NaNs (IEEE 754). The SQL standards do not specify how floating point works in detail. [...]
   > 
   > ### Rules
   > -  -0 == +0
   > - 1/0 = Infinity
   > - 0/0 == Nan
   > - NaN != anything (even NaN)
   >
   > [...]
   >
   > ### Sort Order (Ascending)
   > - NaN
   > - -Inf
   > - numbers
   > - +Inf
   > - NULL
   
   https://www.vertica.com/docs/9.2.x/HTML/Content/Authoring/SQLReferenceManual/DataTypes/Numeric/DOUBLEPRECISIONFLOAT.htm
   
   **=> Does NOT follow this proposal**
   
   ## SQL Standard
   Not open, and scanning through the drafts I've found does not reveal more than "implementation defined". I trust Vertica when they say:
   
   > The SQL standards do not specify how floating point works in detail.
   
   https://www.vertica.com/docs/9.2.x/HTML/Content/Authoring/SQLReferenceManual/DataTypes/Numeric/DOUBLEPRECISIONFLOAT.htm
   
   **=> Undefined**
   
   ## Rust Std
   Normally floats are only partially ordered, but there is some proposed nightly API that orders them:
   
   > The values are ordered in following order:
   >
   > - Negative quiet NaN
   > - Negative signaling NaN
   > - Negative infinity
   > - Negative numbers
   > - Negative subnormal numbers
   > - Negative zero
   > - Positive zero
   > - Positive subnormal numbers
   > - Positive numbers
   > - Positive infinity
   > - Positive signaling NaN
   > - Positive quiet NaN
   
   
   https://doc.rust-lang.org/nightly/std/primitive.f64.html#method.total_cmp
   
   ## Rust `ordered-float`
   > NaN is sorted as _greater_ than all other values and _equal_ to itself, in contradiction with the IEEE standard.
   
   https://docs.rs/ordered-float/2.2.0/ordered_float/struct.OrderedFloat.html


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