etseidl commented on code in PR #603:
URL: https://github.com/apache/parquet-format/pull/603#discussion_r3813862519
##########
LogicalTypes.md:
##########
@@ -735,41 +732,35 @@ only.
A value resolves to bytes based on which of `inline`, `uri`, `offset`, and
`size` are
set:
-| `inline` | `uri` | `offset` | `size` | Resolves to
|
-|----------|-------|----------|--------|-------------------------------------------------------|
-| set | - | - | - | the inline bytes
|
-| - | set | - | - | whole external file at `uri`
|
-| - | set | set | - | invalid
|
-| - | set | - | set | external `uri`, `[0, size)`
|
-| - | set | set | set | external `uri`, `[offset, offset +
size)` |
-| - | - | set | - | invalid
|
-| - | - | - | set | invalid
|
-| - | - | set | set | this file, `[offset, offset + size)`
(self-reference) |
-| - | - | - | - | nothing - invalid
|
+| `inline` | `uri` | `offset` | `size` | Resolves to
|
+|----------|-------|----------|--------|-------------------------------------------|
+| set | - | - | - | the inline bytes
|
+| - | set | - | - | whole external file at `uri`
|
+| - | set | set | - | invalid
|
+| - | set | - | set | external `uri`, `[0, size)`
|
+| - | set | set | set | external `uri`, `[offset, offset +
size)` |
+| - | - | set | - | invalid
|
+| - | - | - | set | invalid
|
+| - | - | set | set | invalid
|
+| - | - | - | - | nothing - invalid
|
`size` must be set whenever `offset` is set, so any offset-based read always
carries an
-explicit `size`. A self-reference (`uri` not set) must set `offset`, and
therefore also
-`size`. `size` may be omitted only for a whole-file external reference, where
the range
-runs to the end of the referenced file.
+explicit `size`. `size` may be omitted only for a whole-file external
reference, where
+the range runs to the end of the referenced file. A byte range within the
current file
+cannot be referenced: `offset` and `size` apply only to data referenced by
`uri`.
Review Comment:
My point is that
> A byte range within the current file cannot be referenced
implies self-reference is disallowed, but the `uri` hack is seemingly still
possible. It's these types of grey areas in the spec that always get us in
trouble. I'd be more comfortable either explicitly disallowing self reference
by saying `uri` cannot reference the current file, or discuss the possibility
of self reference and the ramifications (no encryption, no compression), and
perhaps retain the `uri` unset/`offset+size` set form of self reference.
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