reference a value from other linked table

common/build.rs

@@ -19,6 +19,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .type_attribute(".komp_ac.search", serde)
         .type_attribute(".komp_ac.search2", serde)
         .type_attribute(".komp_ac.table_definition", serde)
+        .type_attribute(
+            ".komp_ac.table_definition.ColumnDefinition",
+            "#[serde(default)]",
+        )
         .type_attribute(".komp_ac.table_script", serde)
         .type_attribute(".komp_ac.table_structure", serde)
         .type_attribute(".komp_ac.table_validation", serde)

common/proto/table_definition.proto

@@ -121,9 +121,9 @@ message PostTableDefinitionRequest {
   // allowed.
   string table_name = 1;
 
-  // The table's columns, including its links and stored linked projections.
+  // The table's columns, including its links and stored linked values.
-  // A projection uses field_type FROM(link_column.source_column); its physical
+  // A linked value uses ColumnDefinition.linked_value; its physical type and
-  // type and money metadata are inferred from the linked source column.
+  // money metadata are inferred from the linked source column.
   repeated ColumnDefinition columns = 3;
 
   // Column names to index, matching names declared above. System columns
@@ -276,7 +276,7 @@ message AddTableColumnsRequest {
   string table_name = 2;
 
   // New user-defined columns only. Existing columns cannot be changed here.
-  // Stored linked projections use field_type FROM(link_column.source_column).
+  // Stored linked values use ColumnDefinition.linked_value.
   repeated ColumnDefinition columns = 3;
 
   // Optional indexes for the new columns only.
@@ -359,9 +359,6 @@ message ColumnDefinition {
   //   LINK(table) → BIGINT referencing that table in the same profile, indexed
   //                 automatically. A table may hold several links to the same
   //                 target as long as the columns are named differently.
-  //   FROM(link.source) → stored, read-only copy of an atomic column reached
-  //                 through another column in this definition whose type is
-  //                 LINK(...). SQL type and money metadata are inferred.
   string field_type = 2;
 
   // MONEY rounding applied before a value is stored.
@@ -381,6 +378,19 @@ message ColumnDefinition {
   // Enables a Boolean ledger on Boolean columns. ANY means
   // one true contribution wins; ALL means one false contribution wins.
   BooleanLedgerOperator boolean_ledger = 7;
+
+  // Defines this named column as a stored, read-only value copied through an
+  // existing LINK column. field_type and money metadata are inferred from the
+  // source column and must not be supplied by the caller.
+  optional LinkedValueDefinition linked_value = 8;
+}
+
+message LinkedValueDefinition {
+  // Exact display name of a LINK column in the table being defined.
+  string link_column = 1;
+
+  // Exact display name of an atomic column in the linked table.
+  string source_column = 2;
 }
 
 enum BooleanLedgerOperator {

common/src/proto/komp_ac.table_definition.rs

@@ -25,9 +25,9 @@ pub struct PostTableDefinitionRequest {
     /// allowed.
     #[prost(string, tag = "1")]
     pub table_name: ::prost::alloc::string::String,
-    /// The table's columns, including its links and stored linked projections.
+    /// The table's columns, including its links and stored linked values.
-    /// A projection uses field_type FROM(link_column.source_column); its physical
+    /// A linked value uses ColumnDefinition.linked_value; its physical type and
-    /// type and money metadata are inferred from the linked source column.
+    /// money metadata are inferred from the linked source column.
     #[prost(message, repeated, tag = "3")]
     pub columns: ::prost::alloc::vec::Vec<ColumnDefinition>,
     /// Column names to index, matching names declared above. System columns
@@ -201,7 +201,7 @@ pub struct AddTableColumnsRequest {
     #[prost(string, tag = "2")]
     pub table_name: ::prost::alloc::string::String,
     /// New user-defined columns only. Existing columns cannot be changed here.
-    /// Stored linked projections use field_type FROM(link_column.source_column).
+    /// Stored linked values use ColumnDefinition.linked_value.
     #[prost(message, repeated, tag = "3")]
     pub columns: ::prost::alloc::vec::Vec<ColumnDefinition>,
     /// Optional indexes for the new columns only.
@@ -255,6 +255,7 @@ pub struct PutTableDefinitionResponse {
 }
 /// Describes one user-defined column for a table.
 #[derive(serde::Serialize, serde::Deserialize)]
+#[serde(default)]
 #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct ColumnDefinition {
     /// Public display name for this column; the physical column uses a stable
@@ -292,9 +293,6 @@ pub struct ColumnDefinition {
     /// LINK(table) → BIGINT referencing that table in the same profile, indexed
     /// automatically. A table may hold several links to the same
     /// target as long as the columns are named differently.
-    /// FROM(link.source) → stored, read-only copy of an atomic column reached
-    /// through another column in this definition whose type is
-    /// LINK(...). SQL type and money metadata are inferred.
     #[prost(string, tag = "2")]
     pub field_type: ::prost::alloc::string::String,
     /// MONEY rounding applied before a value is stored.
@@ -316,6 +314,21 @@ pub struct ColumnDefinition {
     #[prost(enumeration = "BooleanLedgerOperator", tag = "7")]
     #[serde(default, alias = "boolean_ledger_operator")]
     pub boolean_ledger: i32,
+    /// Defines this named column as a stored, read-only value copied through an
+    /// existing LINK column. field_type and money metadata are inferred from the
+    /// source column and must not be supplied by the caller.
+    #[prost(message, optional, tag = "8")]
+    pub linked_value: ::core::option::Option<LinkedValueDefinition>,
+}
+#[derive(serde::Serialize, serde::Deserialize)]
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct LinkedValueDefinition {
+    /// Exact display name of a LINK column in the table being defined.
+    #[prost(string, tag = "1")]
+    pub link_column: ::prost::alloc::string::String,
+    /// Exact display name of an atomic column in the linked table.
+    #[prost(string, tag = "2")]
+    pub source_column: ::prost::alloc::string::String,
 }
 /// Response after table creation (success + DDL preview).
 #[derive(serde::Serialize, serde::Deserialize)]

web/src/schema/mod.rs

@@ -1273,6 +1273,7 @@ pub(crate) fn proto_columns(columns: &[ColumnDefinition]) -> Vec<ProtoColumnDefi
             boolean_ledger: 0,
             currency: column.currency.clone(),
             required: column.required,
+            linked_value: None,
         })
         .collect()
 }