fix: table functions output as return instead of schema

This is for consistency with other functions

Author: benbellick

extensions/functions_table.yaml

@@ -28,7 +28,7 @@ table_functions:
             constant: true
         deterministic: true
         sessionDependent: false
-        schema:
+        return:
           names:
             - value
           struct:
@@ -47,7 +47,7 @@ table_functions:
             constant: true
         deterministic: true
         sessionDependent: false
-        schema:
+        return:
           names:
             - value
           struct:
@@ -62,7 +62,7 @@ table_functions:
             description: The ending value of the series (inclusive)
         deterministic: true
         sessionDependent: false
-        schema:
+        return:
           names:
             - value
           struct:
@@ -77,7 +77,7 @@ table_functions:
             description: The ending value of the series (inclusive)
         deterministic: true
         sessionDependent: false
-        schema:
+        return:
           names:
             - value
           struct:
@@ -99,7 +99,7 @@ table_functions:
         sessionDependent: false
         # Schema references type parameter T from list<T>
         # The field type is derived from the list element type
-        schema:
+        return:
           names:
             - element
           struct:

site/docs/expressions/table_functions.md

@@ -30,7 +30,7 @@ Table functions are defined in YAML extension files, similar to scalar, aggregat
 Like scalar functions' return types, table function schemas follow a clear pattern:
 
 !!! note "Required Constraint"
-    **If a table function's YAML definition includes an output schema, the `derived` field MUST be set to `true` in the plan, and the `table_schema` field MUST match the YAML definition (with any type parameters resolved based on the bound argument types).**
+    **If a table function's YAML definition includes a `return` field, the `derived` field MUST be set to `true` in the plan, and the `table_schema` field MUST match the YAML definition (with any type parameters resolved based on the bound argument types).**
 
 **Derived schemas (`derived: true`)** - The schema can be **deterministically derived from the function signature**, including:
 - **Static schemas**: Fixed output regardless of argument values (e.g., `generate_series` always produces `{value: i64}`)
@@ -113,12 +113,12 @@ Table functions are represented as their own relation type, `TableFunctionRel`.
 - **function_reference**: Points to a function anchor referencing the table function definition
 - **arguments**: Must be constant expressions (currently; literals or expressions evaluable without input data)
 - **derived**: Boolean flag indicating schema source:
-  - `true` - Schema determinable from function signature (concrete types or type parameters). **Required when the YAML definition includes a schema.**
-  - `false` - Schema depends on runtime data content. **Only allowed when the YAML definition omits the schema field.**
+  - `true` - Schema determinable from function signature (concrete types or type parameters). **Required when the YAML definition includes a `return` field.**
+  - `false` - Schema depends on runtime data content. **Only allowed when the YAML definition omits the `return` field.**
 - **table_schema**: The output schema (always present). Must match the YAML definition if derived is true (with type parameters resolved). Contains the actual schema whether derived from YAML or provided by the producer.
 - **common**: Standard relation properties (emit, hints, etc.)
 
-**The key distinction:** Set `derived: true` if the schema can be determined by looking at the function signature and argument types in the YAML definition. Set `derived: false` only if the YAML definition omits the schema field because it requires inspecting runtime data content.
+**The key distinction:** Set `derived: true` if the schema can be determined by looking at the function signature and argument types in the YAML definition. Set `derived: false` only if the YAML definition omits the `return` field because it requires inspecting runtime data content.
 
 Table functions can be used anywhere a relation is expected - as a leaf node, or as input to other relational operators like `FilterRel`, `ProjectRel`, etc.
 

site/docs/relations/logical_relations.md

@@ -127,7 +127,7 @@ Like scalar function return types, table function schemas can be concrete types
 | ------------------ | ------------------------------------------------------------ | -------- |
 | Function Reference | Points to a function_anchor defined in the plan, referencing a table function in the extension YAML files | Required |
 | Arguments          | Constant expressions to pass as arguments to the function. Must match the function signature exactly. Must be literals or expressions that can be evaluated without input data. | Required |
-| Derived            | Boolean flag indicating schema source:<br>• `true` - Schema determinable from function signature (concrete or type-parameterized). **Must be true if YAML defines a schema.**<br>• `false` - Schema depends on runtime data content. **Only allowed if YAML omits schema.** | Required |
+| Derived            | Boolean flag indicating schema source:<br>• `true` - Schema determinable from function signature (concrete or type-parameterized). **Must be true if YAML defines a `return` field.**<br>• `false` - Schema depends on runtime data content. **Only allowed if YAML omits `return` field.** | Required |
 | Table Schema       | The output schema (NamedStruct). Always present. **Must match YAML definition (with type parameters resolved) when derived is true.** | Required |
 
 ### Use Cases

text/simple_extensions_schema.yaml

@@ -334,8 +334,8 @@ $defs:
               $ref: "#/$defs/sessionDependent"
             deterministic:
               $ref: "#/$defs/deterministic"
-            schema:
-              # The output schema.
+            return:
+              # The output schema (NamedStruct).
               # Omit this field only if the schema depends on runtime data content
               # (not determinable from function signature).
               $ref: "#/$defs/type"