ircd::db: Add interface to query size of key in column.

include/ircd/db/column.h

@@ -44,6 +44,10 @@ namespace ircd::db
 	bool cached(column &, const string_view &key, const gopts & = {});
 	void prefetch(column &, const string_view &key, const gopts & = {});
 
+	// [GET] Query space usage
+	size_t bytes(column &, const std::pair<string_view, string_view> &range, const gopts & = {});
+	size_t bytes_value(column &, const string_view &key, const gopts & = {});
+
 	// [GET] Convenience functions to copy data into your buffer.
 	string_view read(column &, const string_view &key, const mutable_buffer &, const gopts & = {});
 	std::string read(column &, const string_view &key, const gopts & = {});

ircd/db.cc

@@ -5520,6 +5520,38 @@ ircd::db::write(column &column,
 	};
 }
 
+size_t
+ircd::db::bytes_value(column &column,
+                      const string_view &key,
+                      const gopts &gopts)
+{
+	size_t ret{0};
+	column(key, std::nothrow, gopts, [&ret]
+	(const string_view &value)
+	{
+		ret = value.size();
+	});
+
+	return ret;
+}
+
+size_t
+ircd::db::bytes(column &column,
+                const std::pair<string_view, string_view> &key,
+                const gopts &gopts)
+{
+	database &d(column);
+	database::column &c(column);
+	const rocksdb::Range range[1]
+	{
+		{ slice(key.first), slice(key.second) }
+	};
+
+	uint64_t ret[1] {0};
+	d.d->GetApproximateSizes(c, range, 1, ret);
+	return ret[0];
+}
+
 void
 ircd::db::prefetch(column &column,
                    const string_view &key,

modules/console.cc

@@ -3159,7 +3159,7 @@ try
 {
 	const params param{line, " ",
 	{
-		"dbname", "column"
+		"dbname", "column", "key"
 	}};
 
 	auto &database
@@ -3167,7 +3167,7 @@ try
 		db::database::get(param.at(0))
 	};
 
-	if(!param[1] || param[1] == "*")
+	if(!param["column"] || param["column"] == "*")
 	{
 		const auto bytes
 		{
@@ -3178,6 +3178,61 @@ try
 		return true;
 	}
 
+	if(param["key"])
+	{
+		db::column column
+		{
+			database, param["column"]
+		};
+
+		const bool is_integer_key
+		{
+			try_lex_cast<ulong>(param["key"])
+		};
+
+		const uint64_t integer_key[2]
+		{
+			is_integer_key?
+				lex_cast<ulong>(param["key"]):
+				0UL,
+
+			integer_key[0] + 1
+		};
+
+		const string_view key[2]
+		{
+			is_integer_key?
+				byte_view<string_view>{integer_key[0]}:
+				param["key"],
+
+			is_integer_key?
+				byte_view<string_view>{integer_key[1]}:
+				param["key"]
+		};
+
+		const auto value
+		{
+			db::bytes_value(column, key[0])
+		};
+
+		const auto value_compressed
+		{
+			db::bytes(column, {key[0], key[1]})
+		};
+
+		out << param["column"]
+		    << (is_integer_key? "[(binary)" : "[") << param["key"] << "] "
+		    << ": " << value << " (uncompressed value)"
+		    << std::endl;
+
+		out << param["column"]
+		    << (is_integer_key? "[(binary)" : "[") << param["key"] << "] "
+		    << ": " << value_compressed
+		    << std::endl;
+
+		return true;
+	}
+
 	const auto query{[&out, &database]
 	(const string_view &colname)
 	{
@@ -3196,15 +3251,15 @@ try
 		    << std::endl;
 	}};
 
-	if(param[1] != "**")
+	if(param["column"] == "**")
 	{
-		query(param.at(1));
+		for(const auto &column : database.columns)
+			query(name(*column));
+
 		return true;
 	}
 
-	for(const auto &column : database.columns)
-		query(name(*column));
-
+	query(param["column"]);
 	return true;
 }
 catch(const std::out_of_range &e)