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 {}{}{} = ?",
-
-    nanodbc::string query = fromUTF8( fmt::format( "SELECT * FROM {}{}{} WHERE {}{}{} = ?",
                                         m_quoteChar, tableName, m_quoteChar,
-                                                   m_quoteChar, columnName, 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;
 }
 

common/database/database_lib_settings.cpp

@@ -96,6 +96,10 @@ DATABASE_LIB_SETTINGS::DATABASE_LIB_SETTINGS( const std::string& aFilename ) :
                 }
             },
             {} ) );
+
+    m_params.emplace_back( new PARAM<int>( "cache.max_size", &m_Cache.max_size, 256 ) );
+
+    m_params.emplace_back( new PARAM<int>( "cache.max_age", &m_Cache.max_age, 10 ) );
 }
 
 

eeschema/sch_plugins/database/sch_database_plugin.cpp

@@ -236,6 +236,8 @@ void SCH_DATABASE_PLUGIN::ensureConnection()
 
             THROW_IO_ERROR( msg );
         }
+
+        m_conn->SetCacheParams( m_settings->m_Cache.max_size, m_settings->m_Cache.max_age );
     }
 }
 

include/database/database_cache.h

@@ -0,0 +1,100 @@
+/*
+ * This program source code file is part of KiCad, a free EDA CAD application.
+ *
+ * Copyright (C) 2022 Jon Evans <jon@craftyjon.com>
+ * Copyright (C) 2022 KiCad Developers, see AUTHORS.txt for contributors.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KICAD_DATABASE_CACHE_H
+#define KICAD_DATABASE_CACHE_H
+
+#include <chrono>
+#include <list>
+#include <string>
+#include <unordered_map>
+
+#include <database/database_connection.h>
+
+
+class DATABASE_CACHE
+{
+public:
+    typedef std::pair<std::string, std::pair<time_t, DATABASE_CONNECTION::ROW>> CACHE_ENTRY;
+
+    DATABASE_CACHE( size_t aMaxSize, time_t aMaxAge ) :
+            m_maxSize( aMaxSize ),
+            m_maxAge( aMaxAge )
+    {}
+
+    void Put( const std::string& aQuery, const DATABASE_CONNECTION::ROW& aResult )
+    {
+        auto it = m_cache.find( aQuery );
+
+        time_t time = std::chrono::system_clock::to_time_t( std::chrono::system_clock::now() );
+
+        m_cacheMru.push_front( std::make_pair( aQuery,
+                                               std::make_pair( time, aResult ) ) );
+
+        if( it != m_cache.end() )
+        {
+            m_cacheMru.erase( it->second );
+            m_cache.erase( it );
+        }
+
+        m_cache[aQuery] = m_cacheMru.begin();
+
+        if( m_cache.size() > m_maxSize )
+        {
+            auto last = m_cacheMru.end();
+            last--;
+            m_cache.erase( last->first );
+            m_cacheMru.pop_back();
+        }
+    }
+
+    bool Get( const std::string& aQuery, DATABASE_CONNECTION::ROW& aResult )
+    {
+        auto it = m_cache.find( aQuery );
+
+        if( it == m_cache.end() )
+            return false;
+
+        time_t time = std::chrono::system_clock::to_time_t( std::chrono::system_clock::now() );
+
+        if( time - it->second->second.first > m_maxAge )
+        {
+            m_cacheMru.erase( it->second );
+            m_cache.erase( it );
+            return false;
+        }
+
+        m_cacheMru.splice( m_cacheMru.begin(), m_cacheMru, it->second );
+
+        aResult = it->second->second.second;
+        return true;
+    }
+
+    void SetMaxSize( size_t aMaxSize ) { m_maxSize = aMaxSize; }
+    void SetMaxAge( time_t aMaxAge ) { m_maxAge = aMaxAge; }
+
+private:
+    size_t m_maxSize;
+    time_t m_maxAge;
+    std::list<CACHE_ENTRY> m_cacheMru;
+    std::unordered_map<std::string, std::list<CACHE_ENTRY>::iterator> m_cache;
+};
+
+#endif //KICAD_DATABASE_CACHE_H

include/database/database_connection.h

@@ -34,6 +34,8 @@ namespace nanodbc
     class connection;
 }
 
+class DATABASE_CACHE;
+
 
 class DATABASE_CONNECTION
 {
@@ -52,6 +54,8 @@ public:
 
     ~DATABASE_CONNECTION();
 
+    void SetCacheParams( int aMaxSize, int aMaxAge );
+
     bool Connect();
 
     bool Disconnect();
@@ -104,6 +108,8 @@ private:
     long m_timeout;
 
     char m_quoteChar;
+
+    std::unique_ptr<DATABASE_CACHE> m_cache;
 };
 
 #endif //KICAD_DATABASE_CONNECTION_H

include/database/database_lib_settings.h

@@ -76,6 +76,13 @@ struct DATABASE_LIB_TABLE
 };
 
 
+struct DATABASE_CACHE_SETTINGS
+{
+    int max_size;    ///< Maximum number of single-row results to cache
+    int max_age;     ///< Max age of cached rows before they expire, in seconds
+};
+
+
 class DATABASE_LIB_SETTINGS : public JSON_SETTINGS
 {
 public:
@@ -87,6 +94,8 @@ public:
 
     std::vector<DATABASE_LIB_TABLE> m_Tables;
 
+    DATABASE_CACHE_SETTINGS m_Cache;
+
 protected:
     wxString getFileExt() const override;
 };