(query) Pre: Model columns that don't have type tags closer to Column.

query-algebrizer/src/clauses/mod.rs

@@ -512,9 +512,6 @@ impl ConjoiningClauses {
         // to get its type, record that we can get it from this table.
         let needs_type_extraction =
             !late_binding &&                                // Never need to extract for bound vars.
-            // Never need to extract types for refs, and var columns are handled elsewhere:
-            // a subquery will be projecting a type tag.
-            column == Column::Fixed(DatomsColumn::Value) &&
             self.known_type(&var).is_none() &&              // Don't need to extract if we know a single type.
             !self.extracted_types.contains_key(&var);       // We're already extracting the type.
 
@@ -523,8 +520,11 @@ impl ConjoiningClauses {
         // If we subsequently find out its type, we'll remove this later -- see
         // the removal in `constrain_var_to_type`.
         if needs_type_extraction {
-            self.extracted_types.insert(var.clone(), alias.for_type_tag());
+            if let Some(tag_alias) = alias.for_associated_type_tag() {
+                self.extracted_types.insert(var.clone(), tag_alias);
             }
+        }
+
         self.column_bindings.entry(var).or_insert(vec![]).push(alias);
     }
 

query-algebrizer/src/types.rs

@@ -127,6 +127,16 @@ impl DatomsColumn {
             ValueTypeTag => "value_type_tag",
         }
     }
+
+    /// The type of the `v` column is determined by the `value_type_tag` column.  Return the
+    /// associated column determining the type of this column, if there is one.
+    pub fn associated_type_tag_column(&self) -> Option<DatomsColumn> {
+        use self::DatomsColumn::*;
+        match *self {
+            Value => Some(ValueTypeTag),
+            _ => None,
+        }
+    }
 }
 
 impl ColumnName for DatomsColumn {
@@ -220,9 +230,12 @@ impl QualifiedAlias {
         QualifiedAlias(table, column.into())
     }
 
-    pub fn for_type_tag(&self) -> QualifiedAlias {
+    pub fn for_associated_type_tag(&self) -> Option<QualifiedAlias> {
-        // TODO: this only makes sense for `DatomsColumn` tables.
+        match self.1 {
-        QualifiedAlias(self.0.clone(), Column::Fixed(DatomsColumn::ValueTypeTag))
+            Column::Fixed(ref c) => c.associated_type_tag_column().map(Column::Fixed),
+            Column::Fulltext(_) => None,
+            Column::Variable(_) => None,
+        }.map(|d| QualifiedAlias(self.0.clone(), d))
     }
 }
 

query-translator/src/translate.rs

@@ -170,7 +170,7 @@ impl ToConstraint for ColumnConstraint {
                 Constraint::equal(left.to_column(), right.to_column()),
 
             Equals(qa, QueryValue::PrimitiveLong(value)) => {
-                let tag_column = qa.for_type_tag().to_column();
+                let tag_column = qa.for_associated_type_tag().expect("an associated type tag alias").to_column();
                 let value_column = qa.to_column();
 
                 // A bare long in a query might match a ref, an instant, a long (obviously), or a