amogh-jahagirdar commented on code in PR #16025:
URL: https://github.com/apache/iceberg/pull/16025#discussion_r4138118201
##########
format/spec.md:
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@@ -742,18 +758,126 @@ The `data_file` struct consists of the following fields:
| | | _optional_ | **`144 content_offset`**
| `long` |
The offset in the file where the content starts [5] |
| | | _optional_ | **`145 content_size_in_bytes`**
| `long` |
The length of a referenced content stored in the file; required if
`content_offset` is present [5] |
-The `partition` struct stores the tuple of partition values for each file. Its
type is derived from the partition fields of the partition spec used to write
the manifest file. In v2, the partition struct's field ids must match the ids
from the partition spec.
+ The `partition` struct stores the tuple of partition values for each file.
Its type is derived from the partition fields of the partition spec used to
write the manifest file. In v2, the partition struct's field ids must match the
ids from the partition spec.
-The v4 `content_stats` container struct stores field-level metrics. Unlike the
metrics maps, the type of `content_stats` is based on table metadata, like
schema. Similar to the `partition` struct, the same type is used for all files
tracked in a manifest.
+ Notes:
+
+ 1. Single-value serialization for lower and upper bounds is detailed in
Appendix D.
+ 2. For `float` and `double`, the value `-0.0` must precede `+0.0`, as in
the IEEE 754 `totalOrder` predicate. NaNs are not permitted as lower or upper
bounds.
+ 3. If sort order ID is missing or unknown, then the order is assumed to be
unsorted. Only data files and equality delete files should be written with a
non-null order id. [Position deletes](#position-delete-files) are required to
be sorted by file and position, not a table order, and should set sort order id
to null. Readers must ignore sort order id for position delete files.
+ 4. Position delete metadata can use `referenced_data_file` when all
deletes tracked by the entry are in a single data file. Setting the referenced
file is required for deletion vectors.
+ 5. The `content_offset` and `content_size_in_bytes` fields are used to
reference a specific blob for direct access to a deletion vector. For deletion
vectors, these values are required and must exactly match the `offset` and
`length` stored in the Puffin footer for the deletion vector blob.
+ 6. The following field ids are reserved on `data_file`: 141.
+
+=== "v4"
+ **Tracked Files**
+
+ | Field id | Name | Type | Required | Description |
+ |----------|------|------|----------|-------------|
+ | 134 | **`content_type`** | `int` (0: DATA, 3: DATA_MANIFEST, 4:
DELETE_MANIFEST) | *required* | Type of content stored in the entry. |
Review Comment:
I honestly forgot why I had named it `content_type`.
I think in the way older proposals I had MDVs not attached to the manifest
itself, and so the name content was conflicting with actual inline content vs
type.
now that it's not modeled that way (MDVs are just with the manifest
itself), it's a little more of a question mark if the `type` suffix is buying
us anything? I still think it's maybe better to suffix with `type` in case in
future format versions there's some actual inline content we avoid conflicting
there. At the same time, renaming things (even though field IDs are the same)
needlessly also isn't great.
Can go either way on this, any thoughts @rdblue @anoopj @stevenzwu
@RussellSpitzer ?
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