Fix for "text type with an unknown/unsupported collation cannot be ha…

…shed" error (vitessio#13852)

go/test/endtoend/preparestmt/stmt_methods_test.go

@@ -436,3 +436,24 @@ func TestShowColumns(t *testing.T) {
 	require.Len(t, cols, 6)
 	require.False(t, rows.Next())
 }
+
+func TestBinaryColumn(t *testing.T) {
+	defer cluster.PanicHandler(t)
+	dbo := Connect(t, "interpolateParams=false")
+	defer dbo.Close()
+
+	_, err := dbo.Query(`SELECT DISTINCT
+                BINARY table_info.table_name AS table_name,
+                table_info.create_options AS create_options,
+                table_info.table_comment AS table_comment
+              FROM information_schema.tables AS table_info
+              JOIN information_schema.columns AS column_info
+                  ON BINARY column_info.table_name = BINARY table_info.table_name
+              WHERE
+                  table_info.table_schema = ?
+                  AND column_info.table_schema = ?
+                  -- Exclude views.
+                  AND table_info.table_type = 'BASE TABLE'
+              ORDER BY BINARY table_info.table_name`, keyspaceName, keyspaceName)
+	require.NoError(t, err)
+}

go/vt/vtgate/semantics/semantic_state.go

@@ -260,6 +260,15 @@ func (st *SemTable) TypeForExpr(e sqlparser.Expr) (sqltypes.Type, collations.ID,
 	if typ, found := st.ExprTypes[e]; found {
 		return typ.Type, typ.Collation, true
 	}
+
+	// We add a lot of WeightString() expressions to queries at late stages of the planning,
+	// which means that they don't have any type information. We can safely assume that they
+	// are VarBinary, since that's the only type that WeightString() can return.
+	_, isWS := e.(*sqlparser.WeightStringFuncExpr)
+	if isWS {
+		return sqltypes.VarBinary, collations.CollationBinaryID, true
+	}
+
 	return sqltypes.Unknown, collations.Unknown, false
 }