huaxingao commented on code in PR #17822:
URL: https://github.com/apache/iceberg/pull/17822#discussion_r4287193230
##########
format/spec.md:
##########
@@ -1197,6 +1333,8 @@ Table metadata consists of the following fields:
| _optional_ | **`partition-statistics`** | A list (optional) of
[partition statistics](#partition-statistics). |
| _required_ | **`next-row-id`** | A `long` higher than all
assigned row IDs; the next snapshot's `first-row-id`. See [Row
Lineage](#row-lineage). |
| _optional_ | **`encryption-keys`** | A list (optional) of
[encryption keys](#encryption-keys) used for table encryption. |
+ | _optional_ | **`last-constraint-id`** | An integer; the highest
assigned constraint ID for the table. This is used to ensure constraints are
always assigned an unused ID. See [Constraints](#constraints). |
+ | _optional_ | **`constraints`** | A list (optional) of
[constraints](#constraints) for the table. |
Review Comment:
Done
##########
format/spec.md:
##########
@@ -655,6 +658,125 @@ Sorting floating-point numbers should produce the
following behavior: `-NaN` < `
A data or delete file is associated with a sort order by the sort order's id
within [a manifest](#manifests). Therefore, the table must declare all the sort
orders for lookup. A table could also be configured with a default sort order
id, indicating how the new data should be sorted by default. Writers should use
this default sort order to sort the data on write, but are not required to if
the default order is prohibitively expensive, as it would be for streaming
writes.
+### Constraints
+
+Constraints are added in v4 and are not supported in v3 or earlier.
+
+A **constraint** declares a condition that a table's rows are expected to
satisfy. Its definition is stored in table metadata. Each snapshot contains the
writer-reported status of each constraint that existed when the snapshot was
created; see [Constraint Validation](#constraint-validation).
+
+Three constraint types are defined:
+
+* `check` -- every row must satisfy a predicate
+* `unique` -- the values of a set of fields must be distinct across the rows
in which every field in the set is non-null; a row in which any field in the
set is null is not compared, so more than one such row may exist
+* `primary-key` -- the values of a set of fields must be distinct across all
rows and must not be null
+
+A constraint is stored separately from the table schema and must refer to
fields by field ID. Constraints may evolve independently from the schema, being
added, modified, or removed.
+
+#### Constraint Fields
+
+A constraint consists of the following fields:
+
+| Requirement | Field name | Type | Description |
+|-------------|---------------------------|-----------|-------------|
+| _required_ | **`constraint-id`** | `int` | ID of the constraint;
unique within the table |
+| _required_ | **`type`** | `string` | The constraint type:
`check`, `unique`, or `primary-key` |
+| _required_ | **`name`** | `string` | A name for the
constraint that is unique within the table. Names are for human consumption and
must not be used to identify a constraint in metadata |
+| _required_ | **`enforced`** | `boolean` | Whether writers must
only add rows that satisfy the constraint |
+| _required_ | **`timestamp-ms`** | `long` | Timestamp in
milliseconds from the unix epoch when the constraint was created or last
modified. The timestamp is informational and must not be used to determine
whether a constraint applies to a snapshot or whether it holds |
+| _optional_ | **`expression`** | `expression` | The predicate that
every row must satisfy, see [Check Constraint
Expressions](#check-constraint-expressions). Required for a `check` constraint
and must not be set for other types |
+| _optional_ | **`field-ids`** | `list<int>` | The set of field IDs
that the constraint applies to. Required for a `unique` or `primary-key`
constraint and must not be set for a `check` constraint |
+
+The fields that define what a constraint requires are embedded directly in the
constraint based on its `type`. Each type carries only the metadata that it
requires: a `check` constraint has an `expression` and must not declare
`field-ids`, and a `unique` or `primary-key` constraint has `field-ids` and
must not declare an `expression`. This keeps a single source of truth for the
fields that a constraint references.
Review Comment:
Agreed. Removed.
##########
format/spec.md:
##########
@@ -655,6 +658,125 @@ Sorting floating-point numbers should produce the
following behavior: `-NaN` < `
A data or delete file is associated with a sort order by the sort order's id
within [a manifest](#manifests). Therefore, the table must declare all the sort
orders for lookup. A table could also be configured with a default sort order
id, indicating how the new data should be sorted by default. Writers should use
this default sort order to sort the data on write, but are not required to if
the default order is prohibitively expensive, as it would be for streaming
writes.
+### Constraints
+
+Constraints are added in v4 and are not supported in v3 or earlier.
+
+A **constraint** declares a condition that a table's rows are expected to
satisfy. Its definition is stored in table metadata. Each snapshot contains the
writer-reported status of each constraint that existed when the snapshot was
created; see [Constraint Validation](#constraint-validation).
+
+Three constraint types are defined:
+
+* `check` -- every row must satisfy a predicate
+* `unique` -- the values of a set of fields must be distinct across the rows
in which every field in the set is non-null; a row in which any field in the
set is null is not compared, so more than one such row may exist
+* `primary-key` -- the values of a set of fields must be distinct across all
rows and must not be null
+
+A constraint is stored separately from the table schema and must refer to
fields by field ID. Constraints may evolve independently from the schema, being
added, modified, or removed.
+
+#### Constraint Fields
+
+A constraint consists of the following fields:
+
+| Requirement | Field name | Type | Description |
+|-------------|---------------------------|-----------|-------------|
+| _required_ | **`constraint-id`** | `int` | ID of the constraint;
unique within the table |
+| _required_ | **`type`** | `string` | The constraint type:
`check`, `unique`, or `primary-key` |
+| _required_ | **`name`** | `string` | A name for the
constraint that is unique within the table. Names are for human consumption and
must not be used to identify a constraint in metadata |
+| _required_ | **`enforced`** | `boolean` | Whether writers must
only add rows that satisfy the constraint |
+| _required_ | **`timestamp-ms`** | `long` | Timestamp in
milliseconds from the unix epoch when the constraint was created or last
modified. The timestamp is informational and must not be used to determine
whether a constraint applies to a snapshot or whether it holds |
+| _optional_ | **`expression`** | `expression` | The predicate that
every row must satisfy, see [Check Constraint
Expressions](#check-constraint-expressions). Required for a `check` constraint
and must not be set for other types |
+| _optional_ | **`field-ids`** | `list<int>` | The set of field IDs
that the constraint applies to. Required for a `unique` or `primary-key`
constraint and must not be set for a `check` constraint |
+
+The fields that define what a constraint requires are embedded directly in the
constraint based on its `type`. Each type carries only the metadata that it
requires: a `check` constraint has an `expression` and must not declare
`field-ids`, and a `unique` or `primary-key` constraint has `field-ids` and
must not declare an `expression`. This keeps a single source of truth for the
fields that a constraint references.
+
+The `field-ids` of a `unique` or `primary-key` constraint must reference
primitive fields and must not reference fields within a `list` or a `map`.
Fields of type `float`, `double`, `geometry`, or `geography` must not be used
because Iceberg does not define equality for them. Fields of type `unknown`
must not be used because their values are always null.
Review Comment:
Fixed. Thanks
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