feat(platform): document count index (#2516)

Co-authored-by: Quantum Explorer <quantum@dash.org>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

packages/rs-dpp/schema/meta_schemas/document/v0/document-meta.json

@@ -426,6 +426,10 @@
               "resolution"
             ],
             "additionalProperties": false
+          },
+          "countable": {
+            "type": "boolean",
+            "description": "Enables countable operations on the index. Adds extra costs for documents storage"
           }
         },
         "required": [

packages/rs-dpp/src/data_contract/document_type/class_methods/try_from_schema/v1/mod.rs

@@ -38,6 +38,8 @@ use crate::consensus::basic::document::MissingPositionsInDocumentTypePropertiesE
 use crate::consensus::basic::token::InvalidTokenPositionError;
 #[cfg(feature = "validation")]
 use crate::consensus::basic::BasicError;
+#[cfg(feature = "validation")]
+use crate::consensus::basic::UnsupportedFeatureError;
 use crate::data_contract::config::v0::DataContractConfigGettersV0;
 use crate::data_contract::config::DataContractConfig;
 use crate::data_contract::document_type::class_methods::try_from_schema::{
@@ -319,6 +321,17 @@ impl DocumentTypeV1 {
 
                         #[cfg(feature = "validation")]
                         if full_validation {
+                            // Countable indices are only supported starting from protocol version 12
+                            if index.countable && platform_version.protocol_version < 12 {
+                                return Err(ProtocolError::ConsensusError(Box::new(
+                                    UnsupportedFeatureError::new(
+                                        "count index".to_string(),
+                                        platform_version.protocol_version,
+                                    )
+                                    .into(),
+                                )));
+                            }
+
                             validation_operations.extend(std::iter::once(
                                 ProtocolValidationOperation::DocumentTypeSchemaIndexValidation(
                                     index.properties.len() as u64,

packages/rs-dpp/src/data_contract/document_type/index/mod.rs

@@ -295,6 +295,8 @@ pub struct Index {
     pub null_searchable: bool,
     /// Contested indexes are useful when a resource is considered valuable
     pub contested_index: Option<ContestedIndexInformation>,
+    /// Enables countable operations on the index
+    pub countable: bool,
 }
 
 impl Index {
@@ -469,6 +471,7 @@ impl TryFrom<&[(Value, Value)]> for Index {
         let mut name = None;
         let mut contested_index = None;
         let mut index_properties: Vec<IndexProperty> = Vec::new();
+        let mut countable = false;
 
         for (key_value, value_value) in index_type_value_map {
             let key = key_value.to_str()?;
@@ -585,6 +588,13 @@ impl TryFrom<&[(Value, Value)]> for Index {
                     }
                     contested_index = Some(contested_index_information);
                 }
+                "countable" => {
+                    countable = value_value
+                        .as_bool()
+                        .ok_or(DataContractError::ValueWrongType(
+                            "countable value must be a boolean".to_string(),
+                        ))?;
+                }
                 "properties" => {
                     let properties =
                         value_value
@@ -627,6 +637,7 @@ impl TryFrom<&[(Value, Value)]> for Index {
             unique,
             null_searchable,
             contested_index,
+            countable,
         })
     }
 }
@@ -680,6 +691,7 @@ mod tests {
             unique,
             null_searchable: true,
             contested_index: None,
+            countable: false,
         }
     }
 

packages/rs-dpp/src/data_contract/document_type/index/random_index.rs

@@ -60,6 +60,7 @@ impl Index {
             unique,
             null_searchable: true,
             contested_index: None,
+            countable: false,
         })
     }
 }