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Applied patch from Juergen that adds a connection pool to the postgre… 
…s provider

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@7268 c8812cc2-4d05-0410-92ff-de0c093fc19c
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mhugent committed Oct 12, 2007
1 parent c03502e commit 820cb45
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Showing 2 changed files with 108 additions and 50 deletions.
146 changes: 96 additions & 50 deletions src/providers/postgres/qgspostgresprovider.cpp
View file
Expand Up @@ -97,7 +97,6 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
else
mSchemaTableName = "\"" + mTableName + "\"";


QgsDebugMsg("Table name is " + mTableName);
QgsDebugMsg("SQL is " + sqlWhereClause);
QgsDebugMsg("Connection info is " + mUri.connInfo);
Expand All @@ -110,37 +109,18 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
//pLog.open((const char *)logFile);
//QgsDebugMsg("Opened log file for " + mTableName);

PGconn *pd = PQconnectdb((const char *) mUri.connInfo);
// check the connection status
if (PQstatus(pd) != CONNECTION_OK)
{
QgsDebugMsg("Connection to database failed");
valid = false;
return;
}

// store the connection for future use
connection = pd;

//set client encoding to unicode because QString uses UTF-8 anyway
QgsDebugMsg("setting client encoding to UNICODE");

int errcode=PQsetClientEncoding(connection, "UNICODE");

if(errcode==0) {
QgsDebugMsg("encoding successfully set");
} else if(errcode==-1) {
QgsDebugMsg("error in setting encoding");
} else {
QgsDebugMsg("undefined return value from encoding setting");
connection = connectDb( (const char *)mUri.connInfo );
if( connection==NULL ) {
valid = false;
return;
}

QgsDebugMsg("Checking for select permission on the relation\n");

// Check that we can read from the table (i.e., we have
// select permission).
QString sql = "select * from " + mSchemaTableName + " limit 1";
PGresult* testAccess = PQexec(pd, (const char*)(sql.utf8()));
PGresult* testAccess = PQexec(connection, (const char*)(sql.utf8()));
if (PQresultStatus(testAccess) != PGRES_TUPLES_OK)
{
showMessageBox(tr("Unable to access relation"),
Expand All @@ -150,33 +130,19 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
"SQL: " + sql);
PQclear(testAccess);
valid = false;
PQfinish(connection);
disconnectDb();
return;
}
PQclear(testAccess);

/* Check to see if we have GEOS support and if not, warn the user about
the problems they will see :) */
QgsDebugMsg("Checking for GEOS support");

if(!hasGEOS(pd))
{
showMessageBox(tr("No GEOS Support!"),
tr("Your PostGIS installation has no GEOS support.\n"
"Feature selection and identification will not "
"work properly.\nPlease install PostGIS with "
"GEOS support (http://geos.refractions.net)"));
}
//--std::cout << "Connection to the database was successful\n";

if (!getGeometryDetails()) // gets srid and geometry type
{
// the table is not a geometry table
numberFeatures = 0;
valid = false;

QgsDebugMsg("Invalid Postgres layer");
PQfinish(connection);
disconnectDb();
return;
}

Expand All @@ -187,14 +153,14 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
// Get the relation oid for use in later queries
sql = "SELECT oid FROM pg_class WHERE relname = '" + mTableName + "' AND relnamespace = ("
"SELECT oid FROM pg_namespace WHERE nspname = '" + mSchemaName + "')";
PGresult *tresult= PQexec(pd, (const char *)(sql.utf8()));
PGresult *tresult= PQexec(connection, (const char *)(sql.utf8()));
QString tableoid = PQgetvalue(tresult, 0, 0);
PQclear(tresult);

// Get the table description
sql = "SELECT description FROM pg_description WHERE "
"objoid = " + tableoid + " AND objsubid = 0";
tresult = PQexec(pd, (const char*) sql.utf8());
tresult = PQexec(connection, (const char*) sql.utf8());
if (PQntuples(tresult) > 0)
mDataComment = PQgetvalue(tresult, 0, 0);
PQclear(tresult);
Expand All @@ -203,7 +169,7 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
// field name, type, length, and precision (if numeric)
sql = "select * from " + mSchemaTableName + " limit 0";

PGresult *result = PQexec(pd, (const char *) (sql.utf8()));
PGresult *result = PQexec(connection, (const char *) (sql.utf8()));
//--std::cout << "Field: Name, Type, Size, Modifier:" << std::endl;

// The queries inside this loop could possibly be combined into one
Expand All @@ -221,20 +187,20 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)
"oid = (SELECT typelem FROM pg_type WHERE "
"typelem = " + typOid + " AND typlen = -1)";

PGresult* oidResult = PQexec(pd, (const char *) sql);
PGresult* oidResult = PQexec(connection, (const char *) sql);
QString fieldTypeName = PQgetvalue(oidResult, 0, 0);
QString fieldSize = PQgetvalue(oidResult, 0, 1);
PQclear(oidResult);

sql = "SELECT attnum FROM pg_attribute WHERE "
"attrelid = " + tableoid + " AND attname = '" + fieldName + "'";
PGresult *tresult = PQexec(pd, (const char *)(sql.utf8()));
PGresult *tresult = PQexec(connection, (const char *)(sql.utf8()));
QString attnum = PQgetvalue(tresult, 0, 0);
PQclear(tresult);

sql = "SELECT description FROM pg_description WHERE "
"objoid = " + tableoid + " AND objsubid = " + attnum;
tresult = PQexec(pd, (const char*)(sql.utf8()));
tresult = PQexec(connection, (const char*)(sql.utf8()));
if (PQntuples(tresult) > 0)
fieldComment = PQgetvalue(tresult, 0, 0);
PQclear(tresult);
Expand Down Expand Up @@ -306,7 +272,7 @@ QgsPostgresProvider::QgsPostgresProvider(QString const & uri)

// Close the database connection if the layer isn't going to be loaded.
if (!valid)
PQfinish(connection);
disconnectDb();
}

QgsPostgresProvider::~QgsPostgresProvider()
Expand All @@ -329,13 +295,93 @@ QgsPostgresProvider::~QgsPostgresProvider()
QApplication::sendPostedEvents(this, QGis::ProviderExtentCalcEvent);
QApplication::sendPostedEvents(this, QGis::ProviderCountCalcEvent);
#endif
PQfinish(connection);

disconnectDb();

QgsDebugMsg("deconstructing.");

//pLog.flush();
}

PGconn *QgsPostgresProvider::connectDb(const char *conninfo)
{
if( connections.contains(conninfo) )
{
QgsDebugMsg(QString("Using cached connection for ") + conninfo);
connections[conninfo]->ref++;
return connections[conninfo]->conn;
}

QgsDebugMsg(QString("New postgres connection for ") + conninfo);

PGconn *pd = PQconnectdb(conninfo);
// check the connection status
if (PQstatus(pd) != CONNECTION_OK)
{
QgsDebugMsg("Connection to database failed");
return NULL;
}

//set client encoding to unicode because QString uses UTF-8 anyway
QgsDebugMsg("setting client encoding to UNICODE");

int errcode=PQsetClientEncoding(pd, "UNICODE");

if(errcode==0)
{
QgsDebugMsg("encoding successfully set");
}
else if(errcode==-1)
{
QgsDebugMsg("error in setting encoding");
}
else
{
QgsDebugMsg("undefined return value from encoding setting");
}

/* Check to see if we have GEOS support and if not, warn the user about
the problems they will see :) */
QgsDebugMsg("Checking for GEOS support");

if(!hasGEOS(pd))
{
showMessageBox(tr("No GEOS Support!"),
tr("Your PostGIS installation has no GEOS support.\n"
"Feature selection and identification will not "
"work properly.\nPlease install PostGIS with "
"GEOS support (http://geos.refractions.net)"));
}
//--std::cout << "Connection to the database was successful\n";

Conn *conn = new Conn(pd);
connections.insert( conninfo, conn );

return pd;
}

void QgsPostgresProvider::disconnectDb()
{
QMapIterator <QString, Conn *> i(connections);
while( i.hasNext() )
{
i.next();

if( i.value()->conn == connection )
break;
}

assert( i.value()->conn==connection );
assert( i.value()->ref>0 );

if( --i.value()->ref==0 )
{
PQfinish( i.value()->conn );
delete (i.value());
connections.remove( i.key() );
}
}

QString QgsPostgresProvider::storageType()
{
return "PostgreSQL database with PostGIS extension";
Expand Down Expand Up @@ -434,7 +480,6 @@ bool QgsPostgresProvider::getNextFeature(QgsFeature& feature)
} // if new queue is required

// Now return the next feature from the queue

feature = mFeatureQueue.front();
mFeatureQueue.pop();

Expand Down Expand Up @@ -2609,3 +2654,4 @@ QGISEXTERN bool isProvider(){
return true;
}

QMap<QString, QgsPostgresProvider::Conn *> QgsPostgresProvider::connections;
12 changes: 12 additions & 0 deletions src/providers/postgres/qgspostgresprovider.h
View file
Expand Up @@ -546,6 +546,18 @@ class QgsPostgresProvider:public QgsVectorDataProvider
*/
void customEvent ( QCustomEvent * e );

private:
struct Conn {
Conn(PGconn *connection) : ref(1), conn(connection) {}

int ref;
PGconn *conn;
};

PGconn *connectDb(const char *conninfo);
void disconnectDb();

static QMap<QString, Conn *> connections;
};

#endif

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