feat: add dynamic parameter expression

proto/substrait/algebra.proto

@@ -957,6 +957,7 @@ message Expression {
     Cast cast = 11;
     Subquery subquery = 12;
     Nested nested = 13;
+    DynamicParameter dynamic_parameter = 14;
 
     // deprecated: enum literals are only sensible in the context of
     // function arguments, for which FunctionArgument should now be
@@ -1611,6 +1612,16 @@ message Expression {
   }
 }
 
+// Expression that represents a dynamic parameter.
+// Dynamic parameters are identified by a surrogate key within a plan.
+message DynamicParameter {
+  // The type of the dynamic parameter.
+  Type type = 1;
+
+  // The surrogate key used within a plan to reference a specific parameter binding.
+  uint32 parameter_anchor = 2;
+}
+
 // The description of a field to sort on (including the direction of sorting and null semantics)
 message SortField {
   Expression expr = 1;

proto/substrait/plan.proto

@@ -46,6 +46,11 @@ message Plan {
   // unused. In many cases, a consumer may be able to work with a plan even if
   // one or more message types defined here are unknown.
   repeated string expected_type_urls = 5;
+
+  // An optional list of bindings for dynamic parameters used in this plan.
+  // The index of each entry in the list corresponds to the parameter_anchor
+  // of a DynamicParameter expression, mapping it to its runtime value.
+  repeated Expression.Literal parameter_bindings = 7;
 }
 
 // This message type can be used to deserialize only the version of a Substrait

site/docs/expressions/_config

@@ -7,3 +7,4 @@ arrange:
   - table_functions.md
   - user_defined_functions.md
   - embedded_functions.md
+  - dynamic_parameters.md

site/docs/expressions/dynamic_parameters.md

@@ -0,0 +1,12 @@
+# Dynamic Parameter Expression
+
+The dynamic parameter expression represents a placeholder within an expression whose value is determined at runtime.
+This is particularly useful for parameterized queries where certain values are not known until execution.
+Additionally, using dynamic parameters can enable other use cases, such as sharing execution plans without embedding sensitive information.
+
+A dynamic parameter expression includes the following properties:
+
+| Property           | Description                                                                   | Required |
+|--------------------|-------------------------------------------------------------------------------|----------|
+| `type`             | Specifies the expected data type of the dynamic parameter.                    | Yes      |
+| `parameter_anchor` | A surrogate key used within a plan to reference a specific parameter binding. | Yes      |

site/docs/relations/basics.md

@@ -73,6 +73,14 @@ A guarantee that data output from this operation is provided with a sort order.
 | Clustered                  | Ensures that all equal values are coalesced (but no ordering between values is defined). E.g. for values 1,2,3,1,2,3, output could be any of the following: 1,1,2,2,3,3 or 1,1,3,3,2,2 or 2,2,1,1,3,3 or 2,2,3,3,1,1 or 3,3,1,1,2,2 or 3,3,2,2,1,1. | N/A, may appear anywhere but will be coalesced. |
 
 
+## Dynamic Parameters
+
+Dynamic parameters act as placeholders within expressions, with their values determined at runtime.
+This is particularly useful for *parameterized queries*,  *query reuse*, and  *execution plan sharing*, where specific values are not known ahead of time or need to be replaced dynamically during execution.
+
+### Dynamic Parameter Bindings
+In a plan's relational tree, dynamic parameters are referenced in expressions without predefined values.
+Their values are supplied via parameter bindings, which can either be included in the plan's optional bindings field or supplied separately at execution time.