postgis: allow for altering the default behavior of keeping open postgresql connections until the whole process ends - when 'persist_connection' = false new connections will be opened and closed for each datasource instance. (closes #434)

CHANGELOG

@@ -15,6 +15,9 @@ For a complete change history, see the SVN log.
 Mapnik 0.6.2 Release
 --------------------
 
+- PostGIS: Add a 'persist_connection' option (default true), that when false will release 
+  the idle psql connection after datasource goes out of scope (r1337) (#433,#434)
+
 - Filters: Add support for '!=' as an alias to '<>' for not-equals filters (avoids &lt;&gt;) (r1326) (#427)  
 
 - Gdal Plugin: Add support for Gdal overviews, enabling fast loading of > 1GB rasters (r1321) (#54)

plugins/input/postgis/connection.hpp

@@ -40,9 +40,11 @@ class Connection
    private:
       PGconn *conn_;
       int cursorId;
+      bool closed_;
    public:
       Connection(std::string const& connection_str)
-         :cursorId(0)
+         :cursorId(0),
+         closed_(false)
       {
          conn_=PQconnectdb(connection_str.c_str());
          if (PQstatus(conn_) != CONNECTION_OK)
@@ -67,6 +69,7 @@ class Connection
          PQclear(result);
          return ok;
       }
+      
       boost::shared_ptr<ResultSet> executeQuery(const std::string& sql,int type=0) const
       {
          PGresult *result=0;
@@ -109,7 +112,14 @@ class Connection
       
       void close()
       {
-         PQfinish(conn_);
+         if (!closed_)
+         {
+             PQfinish(conn_);
+#ifdef MAPNIK_DEBUG
+             std::clog << "PostGIS: datasource closed, also closing connection - " << conn_ << "\n";
+#endif
+             closed_ = true;
+         }
       }
       
       std::string new_cursor_name()
@@ -121,10 +131,14 @@ class Connection
       
       ~Connection()
       {
-         PQfinish(conn_);
+         if (!closed_)
+         {
+             PQfinish(conn_);
 #ifdef MAPNIK_DEBUG
-         std::clog << "close connection " << conn_ << "\n";
-#endif 
+             std::clog << "PostGIS: postgresql connection closed - " << conn_ << "\n";
+#endif
+             closed_ = true;
+         }
       }
 };
 

plugins/input/postgis/postgis.cpp

@@ -76,11 +76,23 @@ postgis_datasource::postgis_datasource(parameters const& params)
               params.get<std::string>("dbname"),
               params.get<std::string>("user"),
               params.get<std::string>("password")),
-     bbox_token_("!bbox!")
+     bbox_token_("!bbox!"),
+     persist_connection_(*params_.get<mapnik::boolean>("persist_connection",true))
 {   
 
-   if (table_.empty()) throw mapnik::datasource_exception("missing <table> parameter");
-   
+   if (table_.empty()) throw mapnik::datasource_exception("PostGIS: missing <table> parameter");
+
+#ifdef MAPNIK_DEBUG
+   if (persist_connection_)
+   {
+       clog << "PostGIS: persisting connection pool..." << endl;
+   }
+   else
+   {
+       clog << "PostGIS: not persisting connection..." << endl;   
+   }
+#endif
+
    boost::optional<int> initial_size = params_.get<int>("inital_size",1);
    boost::optional<int> max_size = params_.get<int>("max_size",10);
 
@@ -257,7 +269,7 @@ postgis_datasource::postgis_datasource(parameters const& params)
                case 25:    // text
                   desc_.add_descriptor(attribute_descriptor(fld_name,mapnik::String));
                   break;
-               default: // shouldn't get here
+               default: // shouldn not get here
 #ifdef MAPNIK_DEBUG
                   clog << "unknown type_oid="<<type_oid<<endl;
 #endif
@@ -490,4 +502,19 @@ Envelope<double> postgis_datasource::envelope() const
    return extent_;
 }
 
-postgis_datasource::~postgis_datasource() {}
+postgis_datasource::~postgis_datasource() 
+{
+    if (!persist_connection_)
+    {
+        ConnectionManager *mgr=ConnectionManager::instance();
+        shared_ptr<Pool<Connection,ConnectionCreator> > pool=mgr->getPool(creator_.id());
+        if (pool)
+        {
+            shared_ptr<Connection> conn = pool->borrowObject();
+            if (conn)
+            {
+                conn->close();
+            }
+        }
+    }
+}

plugins/input/postgis/postgis.hpp

@@ -70,6 +70,7 @@ class postgis_datasource : public datasource
       bool multiple_geometries_;
       static const std::string name_;
       const std::string bbox_token_;
+      bool persist_connection_;
    public:
       static std::string name();
       int type() const;