DbLib: Add single-row query cache

Since single-row queries are performed rapid-fire during certain actions like
stepping through the symbol browser, there is high value in caching them for
a small amount of time.  The default cache parameters will keep results for
10 seconds, which errs on the side of getting fresh data from the database
on most user interactions.

common/database/database_connection.cpp

@@ -43,6 +43,7 @@
 #include <wx/log.h>
 
 #include <database/database_connection.h>
+#include <database/database_cache.h>
 
 
 const char* const traceDatabase = "KICAD_DATABASE";
@@ -88,6 +89,8 @@ DATABASE_CONNECTION::DATABASE_CONNECTION( const std::string& aDataSourceName,
     m_pass    = aPassword;
     m_timeout = aTimeoutSeconds;
 
+    m_cache = std::make_unique<DATABASE_CACHE>( 10, 1 );
+
     if( aConnectNow )
         Connect();
 }
@@ -100,6 +103,8 @@ DATABASE_CONNECTION::DATABASE_CONNECTION( const std::string& aConnectionString,
     m_connectionString = aConnectionString;
     m_timeout          = aTimeoutSeconds;
 
+    m_cache = std::make_unique<DATABASE_CACHE>( 10, 1 );
+
     if( aConnectNow )
         Connect();
 }
@@ -112,6 +117,22 @@ DATABASE_CONNECTION::~DATABASE_CONNECTION()
 }
 
 
+void DATABASE_CONNECTION::SetCacheParams( int aMaxSize, int aMaxAge )
+{
+    if( !m_cache )
+        return;
+
+    if( aMaxSize < 0 )
+        aMaxSize = 0;
+
+    if( aMaxAge < 0 )
+        aMaxAge = 0;
+
+    m_cache->SetMaxSize( static_cast<size_t>( aMaxSize ) );
+    m_cache->SetMaxAge( static_cast<time_t>( aMaxAge ) );
+}
+
+
 bool DATABASE_CONNECTION::Connect()
 {
     nanodbc::string dsn  = fromUTF8( m_dsn );
@@ -301,11 +322,19 @@ bool DATABASE_CONNECTION::SelectOne( const std::string& aTable,
 
     const std::string& columnName = columnCacheIter->first;
 
-    nanodbc::statement statement( *m_conn );
+    std::string queryStr = fmt::format( "SELECT * FROM {}{}{} WHERE {}{}{} = ?",
+                                        m_quoteChar, tableName, m_quoteChar,
+                                        m_quoteChar, columnName, m_quoteChar );
 
-    nanodbc::string query = fromUTF8( fmt::format( "SELECT * FROM {}{}{} WHERE {}{}{} = ?",
-                                                   m_quoteChar, tableName, m_quoteChar,
-                                                   m_quoteChar, columnName, m_quoteChar ) );
+    nanodbc::statement statement( *m_conn );
+    nanodbc::string query = fromUTF8( queryStr );
+
+    if( m_cache->Get( queryStr, aResult ) )
+    {
+        wxLogTrace( traceDatabase, wxT( "SelectOne: `%s` with parameter `%s` - cache hit" ),
+                    toUTF8( query ), aWhere.second );
+        return true;
+    }
 
     try
     {
@@ -364,6 +393,8 @@ bool DATABASE_CONNECTION::SelectOne( const std::string& aTable,
         return false;
     }
 
+    m_cache->Put( queryStr, aResult );
+
     return true;
 }