Add an index for the muc_log_line table

This immensely speeds up the archive select queries.

fix #3292

src/database/database.cpp

@@ -6,6 +6,8 @@
 #include <utils/get_first_non_empty.hpp>
 #include <utils/time.hpp>
 
+#include <database/index.hpp>
+
 #include <sqlite3.h>
 
 sqlite3* Database::db;
@@ -42,6 +44,7 @@ void Database::open(const std::string& filename)
   Database::irc_channel_options.upgrade(Database::db);
   Database::roster.create(Database::db);
   Database::roster.upgrade(Database::db);
+  create_index<Database::Owner, Database::IrcChanName, Database::IrcServerName>(Database::db, "archive_index", Database::muc_log_lines.get_name());
 }
 
 

src/database/index.hpp

+#pragma once
+
+#include <sqlite3.h>
+
+#include <string>
+#include <tuple>
+
+namespace
+{
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N == sizeof...(T), void>::type
+add_column_name(std::string&)
+{ }
+
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N < sizeof...(T), void>::type
+add_column_name(std::string& out)
+{
+  using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<std::tuple<T...>>()))>::type;
+  out += ColumnType::name;
+  if (N != sizeof...(T) - 1)
+    out += ",";
+  add_column_name<N+1, T...>(out);
+}
+}
+
+template <typename... Columns>
+void create_index(sqlite3* db, const std::string& name, const std::string& table)
+{
+  std::string res{"CREATE INDEX IF NOT EXISTS "};
+  res += name + " ON " + table + "(";
+  add_column_name<0, Columns...>(res);
+  res += ")";
+
+  char* error;
+  const auto result = sqlite3_exec(db, res.data(), nullptr, nullptr, &error);
+  if (result != SQLITE_OK)
+    {
+      log_error("Error executing query: ", error);
+      sqlite3_free(error);
+    }
+}