singhpk234 commented on code in PR #13879:
URL: https://github.com/apache/iceberg/pull/13879#discussion_r2492820857
##########
open-api/rest-catalog-open-api.yaml:
##########
@@ -3265,6 +3265,136 @@ components:
additionalProperties:
type: string
+ ReadRestrictions:
+ type: object
+ description: >
+ Read restrictions for a table, including projections and row filter
expressions, according to the current schema.
+
+ A client MUST enforce the restrictions defined in this object when
reading data
+ from the table.
+
+ These restrictions apply only to the authenticated principal, user,
or account
+ associated with the client. They MUST NOT be interpreted as global
policy and
+ MUST NOT be applied beyond the entity identified by the
Authentication header
+ (or other applicable authentication mechanism).
+ properties:
+ required-projections:
+ description: >
+ A list of projections that MUST be applied prior to any
query-specified
+ projections.
+ If the required-projection property is absent, no mandatory
projection applies,
+ and a reader MAY project any subset of columns of the table,
including all columns.
+
+ 1. A reader MUST project only columns listed in the
required-projection.
+ - If a listed column has a transform, the reader MUST apply it
and replace
+ all references to the underlying column with the transformed
value
+ (for example, truncate[4](cc) MUST be projected as
truncate[4](cc) AS cc,
+ and all references to cc during query evaluation post applying
required-row-filter MUST resolve to this alias).
+ - Columns not listed in the required-projection MUST NOT be read.
+
+ 2. A column MUST appear at most once in the required-projection.
+
+ 3. Multiple transformed versions of the same column (e.g.,
truncate[5](col)
+ and truncate[3](col) MUST NOT appear in the required-projection.
+
+ 4. If a projection entry includes an action that the reader cannot
evaluate,
+ the reader MUST fail rather than ignore the transform.
+
+ 5. An identity transform is equivalent to projecting the column
directly.
+
+ 8. The data type of the projected column MUST match the data type
defined for the transform result.
+
+ type: array
+ items:
+ $ref: '#/components/schemas/Projection'
+ required-row-filter:
+ description: >
+ An expression that filters rows in the table.
+
+ 1. A reader MUST discard any row for which the filter evaluates to
false or null, and
+ no information derived from discarded rows MAY be included in
the query result.
+
+ 2. Row filters MUST be evaluated against the original,
untransformed column values.
+ Required projections MUST be applied only after row filters are
applied.
+
+ 3. If the catalog supports multiple row access filters for the
table, it is
+ the catalog's responsibility to combine them using the
appropriate logic (e.g., AND, OR).
+
+ 4. If a client cannot interpret or evaluate a provided filter
expression, it MUST fail.
+
+ 5. If the required-row-filter property is absent or empty, no
mandatory filtering is imposed.
+ $ref: '#/components/schemas/Expression'
+
+ Projection:
+ type: object
+ description: Defines a projection for a column.
+ properties:
+ source-id:
+ type: int
+ description: field id of the column being projected.
+ action:
+ $ref: '#/components/schemas/Action'
+ required:
+ - source-id
+ - action
+
+ Action:
Review Comment:
the action like sha256 / null are very well defined like one needs to do
project null for this column ... one option would have been we create
transforms for this and then wrap a scalar expression referecing the transform
which return this value, it seemed like an overkill for this function rather
what we did now is one has an action if its a known mask just execute it, same
is for transform, I wonder if for UDFs we just need apply_udf action ?
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