Hi all,
What's the best way to manage multiple database connections in an
application? Specifically, how can I manage which db connection is
used for models, queries, &c.?
The documentation says that multiple connections can be declared with
a unique name for each on calling addDatabase(). My simple
implementation yields errors and doesn't seem to provide a means to
load data or call queries on one or the other. For example,
db2 = QtSql.QSqlDatabase.addDatabase("QPSQL")
db2.setDatabaseName("foo_db")
db1 = QtSql.QSqlDatabase.addDatabase("QSQLITE")
db1.setDatabaseName(":memory:")
This yields the following errors:
QSqlDatabasePrivate::removeDatabase: connection
'qt_sql_default_connection' is still in use, all queries will cease to
work.
QSqlDatabasePrivate::addDatabase: duplicate connection name
'qt_sql_default_connection', old connection removed.
Then creating and setting a data model uses which database? Both?
self.theModel = QtSql.QSqlTableModel(self)
self.theModel.setTable("color")
See the main() method in the attached example. Thanks in advance!
Scott
#!/usr/bin/env python
import sys, os
from PyQt4 import QtCore, QtGui, QtSql
COLOR_ID, NAME, DESCRIPTION = range(3)
def createFakeData():
query = QtSql.QSqlQuery()
query.exec_("DROP TABLE color")
query.exec_("""CREATE TABLE color (
color_id PRIMARY KEY,
name VARCHAR(32) UNIQUE NOT NULL,
description TEXT NOT NULL)""")
query.exec_("INSERT INTO color (name, description) "
"VALUES ('red', 'this is red')")
query.exec_("INSERT INTO color (name, description) "
"VALUES ('green', 'this is green')")
query.exec_("INSERT INTO color (name, description) "
"VALUES ('blue', 'this is blue')")
#-------------------------------------------------------------------------------
# class
#-------------------------------------------------------------------------------
class DbTestForm(QtGui.QWidget):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self)
# table model
# ------------------------------------------------
self.theModel = QtSql.QSqlTableModel(self)
self.theModel.setTable("color")
self.theModel.setSort(NAME, QtCore.Qt.AscendingOrder)
self.theModel.setEditStrategy(QtSql.QSqlTableModel.OnManualSubmit)
# column headers
self.theModel.setHeaderData(COLOR_ID, QtCore.Qt.Horizontal, QtCore.QVariant("COLOR_ID"))
self.theModel.setHeaderData(NAME, QtCore.Qt.Horizontal, QtCore.QVariant("NAME"))
self.theModel.setHeaderData(DESCRIPTION, QtCore.Qt.Horizontal, QtCore.QVariant("DESCRIPTION"))
select = self.theModel.select()
# table view
# ------------------------------------------------
self.theView = QtGui.QTableView()
self.theView.setSortingEnabled(True)
self.theView.setModel(self.theModel)
self.theView.setSelectionMode(QtGui.QTableView.SingleSelection)
self.theView.setSelectionBehavior(QtGui.QTableView.SelectRows)
self.theView.setColumnHidden(COLOR_ID, True)
self.theView.resizeColumnsToContents()
self.theView.horizontalHeader().setStretchLastSection(True)
# table layout
# ------------------------------------------------
self.tableLayout = QtGui.QVBoxLayout()
self.tableLayout.addWidget(self.theView)
self.setLayout(self.tableLayout)
# table view selection model
# ------------------------------------------------
self.theSelectionModel = self.theView.selectionModel()
# signals/slots
# ------------------------------------------------
self.connect(self.theSelectionModel, QtCore.SIGNAL("selectionChanged(QItemSelection, QItemSelection)"), self.getSelection)
# methods
# ------------------------------------------------
def getSelection(self, selected, deselected):
currentIndex = self.theSelectionModel.currentIndex()
row = currentIndex.row()
selectedIndex = self.theModel.index(row, 2) # column count starts at 1
print "data: ", self.theModel.data(currentIndex).toString()
print "row: ", currentIndex.row()
print "row data: ", self.theModel.data(selectedIndex).toString()
#-------------------------------------------------------------------------------
# main
#-------------------------------------------------------------------------------
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
db2 = QtSql.QSqlDatabase.addDatabase("QPSQL")
db2.setDatabaseName("foo_db")
db1 = QtSql.QSqlDatabase.addDatabase("QSQLITE")
db1.setDatabaseName(":memory:")
if not db1.open():
QtGui.QMessageBox.warning(None, "Test",
QtCore.QString("Database Error: %1").arg(db1.lastError().text()))
sys.exit(1)
ok = db1.open()
print "db1 connection: ", ok
createFakeData()
form = DbTestForm()
form.setWindowTitle("Db Test")
form.show()
sys.exit(app.exec_())
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