ircd::db: Consider if column dropped for boolean test.

include/ircd/db/column.h

@@ -116,8 +116,8 @@ struct ircd::db::column
 	explicit operator database &();
 	explicit operator database::column &();
 
-	explicit operator bool() const               { return bool(c);                                 }
+	explicit operator bool() const;
-	bool operator!() const                       { return !c;                                      }
+	bool operator!() const;
 
 	// [GET] Iterations
 	const_iterator begin(gopts = {});
@@ -294,6 +294,13 @@ const
 	return *c;
 }
 
+inline bool
+ircd::db::column::operator!()
+const
+{
+	return !bool(*this);
+}
+
 inline ircd::db::column::operator
 database::column &()
 {

include/ircd/db/database/column.h

@@ -24,6 +24,7 @@ namespace ircd::db
 	const std::string &name(const database::column &);
 	uint32_t id(const database::column &);
 
+	bool dropped(const database::column &);
 	void drop(database::column &);                   // Request to erase column from db
 }
 

ircd/db.cc

@@ -1599,6 +1599,14 @@ ircd::db::drop(database::column &c)
 	};
 }
 
+bool
+ircd::db::dropped(const database::column &c)
+{
+	return c.descriptor?
+		c.descriptor->drop:
+		true;
+}
+
 uint32_t
 ircd::db::id(const database::column &c)
 {
@@ -5624,6 +5632,15 @@ const
 	return { *this, key };
 }
 
+ircd::db::column::operator
+bool()
+const
+{
+	return c?
+		!dropped(*c):
+		false;
+}
+
 ircd::db::column::operator
 const descriptor &()
 const