aokolnychyi commented on code in PR #7105: URL: https://github.com/apache/iceberg/pull/7105#discussion_r1351072100
########## format/spec.md: ########## @@ -702,6 +703,58 @@ Blob metadata is a struct with the following fields: | _optional_ | _optional_ | **`properties`** | `map<string, string>` | Additional properties associated with the statistic. Subset of Blob properties in the Puffin file. | +#### Partition statistics + +Partition statistics files are based on [Partition Statistics file spec](#partition-statistics-file). +Partition statistics are not required for reading or planning and readers may ignore them. +Each table snapshot may be associated with at most one partition statistic file. +A writer can optionally write the partition statistics file during each write operation, and +it must be registered in the table metadata file to be considered as a valid statistics file for the reader. + +`partition-statistics` field of table metadata is an optional list of struct with the following fields: + +| v1 | v2 | Field name | Type | Description | +|----|----|------------|------|-------------| +| _required_ | _required_ | **`snapshot-id`** | `long` | ID of the Iceberg table's snapshot the partition statistics file is associated with. | +| _required_ | _required_ | **`statistics-file-path`** | `string` | Path of the partition statistics file. See [Partition Statistics file](#partition-statistics-file). | +| _required_ | _required_ | **`file-size-in-bytes`** | `long` | Size of the partition statistics file. | + +#### Partition Statistics file + +Statistics information for each unique partition tuple is stored as a row in the default data file format of the table (for example, Parquet or ORC). +These rows must be sorted (in ascending manner with NULL FIRST) by `partition` field to optimize filtering rows while scanning. + +The schema of the partition statistics file is as follows: + +| v1 | v2 | Field id, name | Type | Description | +|----|----|----------------|------|-------------| +| _required_ | _required_ | **`1 partition`** | `struct<..>` | Partition data tuple, schema based on the unified partition type considering all specs in a table | +| _required_ | _required_ | **`2 spec_id`** | `int` | Partition spec id | Review Comment: I took a look at #8488 and I am not sure I how feel about generating these files during commits (in fact, during each commit attempt). I'd personally start by adding API and core logic to be able to add these files on demand and implement an action to actually produce these files (either incrementally or from scratch). Updating these stats for larger tables in each commit attempt will cause issues. In the action, we can do this more efficiently. We can also call this action immediately after writes but at least it will not be part of the commit. It would also drastically reduce the amount of changes in #8488, we won't have to touch every operation type. -- 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: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
