anoopj commented on code in PR #18585: URL: https://github.com/apache/iceberg/pull/18585#discussion_r4328163929
########## format/spec.md: ########## @@ -1011,12 +1012,35 @@ For example, stats for an optional `geometry` field named `location` with field- 10_804: optional long value_count; 10_805: optional long null_value_count; 10_807: optional long total_bytes; - // tight_bounds and nan_value_count are omitted for geo types + // nan_value_count is omitted for geo types } ``` For `variant`, both bounds are unshredded `variant` that store variant field bounds by normalized JSON paths as field names. See [Bounds for Variant](#bounds-for-variant) for details on producing these bounds. +<a id="stats-tightness"></a> +###### Stats Tightness + +Statistics are *tight* when they are exact for the live rows of a file: + +* Bounds are the minimum and maximum of the live values. +* `null_value_count` and `nan_value_count` are the counts across the live rows. + +`value_count` and `total_bytes` are not part of tightness. `value_count` is the number of values across all rows written to the file and is not adjusted when rows are deleted; for a field with no repeated (`list` or `map`) ancestor, the live value count is `value_count` minus the deletion vector's cardinality. `total_bytes` is an estimate and is likewise not adjusted for deleted rows. + +When `tight_stats` is absent, readers must assume stats are not tight. + +When `tight_stats` is true: + +* `null_value_count` and `nan_value_count` are exact for the live rows. +* Bounds are exact for primitive types other than `string` and `binary`, whose bounds may have been truncated when written. +* `variant` bounds are stored per leaf field and are optional; a leaf field may have no bound, but any bound that is present is exact. +* `geometry` and `geography` bounds are a bounding box that contains the live values, not exact minimum and maximum values. + +A `variant` value is null only when the variant itself is null; a non-null variant that encodes a variant null is not counted as a null value. Variants do not have a `nan_value_count`. Review Comment: Thanks. I dropped the `NaN`-count line, kept the variant-null clause. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
