connector.py

# -*- coding: utf-8 -*-

"""
/***************************************************************************
Name                 : DB Manager
Description          : Database manager plugin for QGIS
Date                 : May 23, 2011
copyright            : (C) 2011 by Giuseppe Sucameli
email                : brush.tyler@gmail.com

The content of this file is based on
- PG_Manager by Martin Dobias <wonder.sk@gmail.com> (GPLv2 license)
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
"""
from builtins import str
from builtins import range

from functools import cmp_to_key

from qgis.PyQt.QtCore import QRegExp, QFile
from qgis.core import Qgis, QgsCredentials, QgsDataSourceUri

from ..connector import DBConnector
from ..plugin import ConnectionError, DbError, Table

import os
import psycopg2
import psycopg2.extensions
# use unicode!
psycopg2.extensions.register_type(psycopg2.extensions.UNICODE)
psycopg2.extensions.register_type(psycopg2.extensions.UNICODEARRAY)


def classFactory():
    return PostGisDBConnector


class PostGisDBConnector(DBConnector):

    def __init__(self, uri):
        DBConnector.__init__(self, uri)

        self.host = uri.host() or os.environ.get('PGHOST')
        self.port = uri.port() or os.environ.get('PGPORT')

        username = uri.username() or os.environ.get('PGUSER')
        password = uri.password() or os.environ.get('PGPASSWORD')

        # Do not get db and user names from the env if service is used
        if not uri.service():
            if username is None:
                username = os.environ.get('USER')
            self.dbname = uri.database() or os.environ.get('PGDATABASE') or username
            uri.setDatabase(self.dbname)

        expandedConnInfo = self._connectionInfo()
        try:
            self.connection = psycopg2.connect(expandedConnInfo)
        except self.connection_error_types() as e:
            # get credentials if cached or asking to the user no more than 3 times
            err = str(e)
            uri = self.uri()
            conninfo = uri.connectionInfo(False)

            for i in range(3):
                (ok, username, password) = QgsCredentials.instance().get(conninfo, username, password, err)
                if not ok:
                    raise ConnectionError(e)

                if username:
                    uri.setUsername(username)

                if password:
                    uri.setPassword(password)

                newExpandedConnInfo = uri.connectionInfo(True)
                try:
                    self.connection = psycopg2.connect(newExpandedConnInfo)
                    QgsCredentials.instance().put(conninfo, username, password)
                except self.connection_error_types() as e:
                    if i == 2:
                        raise ConnectionError(e)
                    err = str(e)
                finally:
                    # clear certs for each time trying to connect
                    self._clearSslTempCertsIfAny(newExpandedConnInfo)
        finally:
            # clear certs of the first connection try
            self._clearSslTempCertsIfAny(expandedConnInfo)

        self.connection.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)

        c = self._execute(None, u"SELECT current_user,current_database()")
        self.user, self.dbname = self._fetchone(c)
        self._close_cursor(c)

        self._checkSpatial()
        self._checkRaster()
        self._checkGeometryColumnsTable()
        self._checkRasterColumnsTable()

    def _connectionInfo(self):
        return str(self.uri().connectionInfo(True))

    def _clearSslTempCertsIfAny(self, connectionInfo):
        # remove certs (if any) of the connectionInfo
        expandedUri = QgsDataSourceUri(connectionInfo)

        def removeCert(certFile):
            certFile = certFile.replace("'", "")
            file = QFile(certFile)
            # set permission to allow removing on Win.
            # On linux and Mac if file is set with QFile::>ReadUser
            # does not create problem removing certs
            if not file.setPermissions(QFile.WriteOwner):
                raise Exception('Cannot change permissions on {}: error code: {}'.format(file.fileName(), file.error()))
            if not file.remove():
                raise Exception('Cannot remove {}: error code: {}'.format(file.fileName(), file.error()))

        sslCertFile = expandedUri.param("sslcert")
        if sslCertFile:
            removeCert(sslCertFile)

        sslKeyFile = expandedUri.param("sslkey")
        if sslKeyFile:
            removeCert(sslKeyFile)

        sslCAFile = expandedUri.param("sslrootcert")
        if sslCAFile:
            removeCert(sslCAFile)

    def _checkSpatial(self):
        """ check whether postgis_version is present in catalog """
        c = self._execute(None, u"SELECT COUNT(*) FROM pg_proc WHERE proname = 'postgis_version'")
        self.has_spatial = self._fetchone(c)[0] > 0
        self._close_cursor(c)
        return self.has_spatial

    def _checkRaster(self):
        """ check whether postgis_version is present in catalog """
        c = self._execute(None, u"SELECT COUNT(*) FROM pg_proc WHERE proname = 'postgis_raster_lib_version'")
        self.has_raster = self._fetchone(c)[0] > 0
        self._close_cursor(c)
        return self.has_raster

    def _checkGeometryColumnsTable(self):
        c = self._execute(None,
                          u"SELECT relkind = 'v' OR relkind = 'm' FROM pg_class WHERE relname = 'geometry_columns' AND relkind IN ('v', 'r', 'm', 'p')")
        res = self._fetchone(c)
        self._close_cursor(c)
        self.has_geometry_columns = (res is not None and len(res) != 0)

        if not self.has_geometry_columns:
            self.has_geometry_columns_access = self.is_geometry_columns_view = False
        else:
            self.is_geometry_columns_view = res[0]
            # find out whether has privileges to access geometry_columns table
            priv = self.getTablePrivileges('geometry_columns')
            self.has_geometry_columns_access = priv[0]
        return self.has_geometry_columns

    def _checkRasterColumnsTable(self):
        c = self._execute(None,
                          u"SELECT relkind = 'v' OR relkind = 'm' FROM pg_class WHERE relname = 'raster_columns' AND relkind IN ('v', 'r', 'm', 'p')")
        res = self._fetchone(c)
        self._close_cursor(c)
        self.has_raster_columns = (res is not None and len(res) != 0)

        if not self.has_raster_columns:
            self.has_raster_columns_access = self.is_raster_columns_view = False
        else:
            self.is_raster_columns_view = res[0]
            # find out whether has privileges to access geometry_columns table
            self.has_raster_columns_access = self.getTablePrivileges('raster_columns')[0]
        return self.has_raster_columns

    def cancel(self):
        if self.connection:
            self.connection.cancel()

    def getInfo(self):
        c = self._execute(None, u"SELECT version()")
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getSpatialInfo(self):
        """ returns tuple about PostGIS support:
                - lib version
                - geos version
                - proj version
                - installed scripts version
                - released scripts version
        """
        if not self.has_spatial:
            return

        try:
            c = self._execute(None,
                              u"SELECT postgis_lib_version(), postgis_geos_version(), postgis_proj_version(), postgis_scripts_installed(), postgis_scripts_released()")
        except DbError:
            return
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def hasSpatialSupport(self):
        return self.has_spatial

    def hasRasterSupport(self):
        return self.has_raster

    def hasCustomQuerySupport(self):
        return Qgis.QGIS_VERSION[0:3] >= "1.5"

    def hasTableColumnEditingSupport(self):
        return True

    def hasCreateSpatialViewSupport(self):
        return True

    def fieldTypes(self):
        return [
            "integer", "bigint", "smallint",  # integers
            "serial", "bigserial",  # auto-incrementing ints
            "real", "double precision", "numeric",  # floats
            "varchar", "varchar(255)", "char(20)", "text",  # strings
            "date", "time", "timestamp"  # date/time
        ]

    def getDatabasePrivileges(self):
        """ db privileges: (can create schemas, can create temp. tables) """
        sql = u"SELECT has_database_privilege(current_database(), 'CREATE'), has_database_privilege(current_database(), 'TEMP')"
        c = self._execute(None, sql)
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getSchemaPrivileges(self, schema):
        """ schema privileges: (can create new objects, can access objects in schema) """
        schema = 'current_schema()' if schema is None else self.quoteString(schema)
        sql = u"SELECT has_schema_privilege(%(s)s, 'CREATE'), has_schema_privilege(%(s)s, 'USAGE')" % {'s': schema}
        c = self._execute(None, sql)
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getTablePrivileges(self, table):
        """ table privileges: (select, insert, update, delete) """

        schema, tablename = self.getSchemaTableName(table)
        schema_priv = self.getSchemaPrivileges(schema)
        if not schema_priv[1]:
            return

        t = self.quoteId(table)
        sql = u"""SELECT has_table_privilege(%(t)s, 'SELECT'), has_table_privilege(%(t)s, 'INSERT'),
                                has_table_privilege(%(t)s, 'UPDATE'), has_table_privilege(%(t)s, 'DELETE')""" % {
            't': self.quoteString(t)}
        c = self._execute(None, sql)
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getSchemas(self):
        """ get list of schemas in tuples: (oid, name, owner, perms) """
        sql = u"SELECT oid, nspname, pg_get_userbyid(nspowner), nspacl, pg_catalog.obj_description(oid) FROM pg_namespace WHERE nspname !~ '^pg_' AND nspname != 'information_schema' ORDER BY nspname"

        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def getTables(self, schema=None, add_sys_tables=False):
        """ get list of tables """
        tablenames = []
        items = []

        sys_tables = ["spatial_ref_sys", "geography_columns", "geometry_columns",
                      "raster_columns", "raster_overviews"]

        try:
            vectors = self.getVectorTables(schema)
            for tbl in vectors:
                if not add_sys_tables and tbl[1] in sys_tables and tbl[2] in ['', 'public']:
                    continue
                tablenames.append((tbl[2], tbl[1]))
                items.append(tbl)
        except DbError:
            pass

        try:
            rasters = self.getRasterTables(schema)
            for tbl in rasters:
                if not add_sys_tables and tbl[1] in sys_tables and tbl[2] in ['', 'public']:
                    continue
                tablenames.append((tbl[2], tbl[1]))
                items.append(tbl)
        except DbError:
            pass

        sys_tables = ["spatial_ref_sys", "geography_columns", "geometry_columns",
                      "raster_columns", "raster_overviews"]

        if schema:
            schema_where = u" AND nspname = %s " % self.quoteString(schema)
        else:
            schema_where = u" AND (nspname != 'information_schema' AND nspname !~ 'pg_') "

        # get all tables and views
        sql = u"""SELECT
                                                cla.relname, nsp.nspname, cla.relkind,
                                                pg_get_userbyid(relowner), reltuples, relpages,
                                                pg_catalog.obj_description(cla.oid)
                                        FROM pg_class AS cla
                                        JOIN pg_namespace AS nsp ON nsp.oid = cla.relnamespace
                                        WHERE cla.relkind IN ('v', 'r', 'm', 'p') """ + schema_where + """
                                        ORDER BY nsp.nspname, cla.relname"""

        c = self._execute(None, sql)
        for tbl in self._fetchall(c):
            if tablenames.count((tbl[1], tbl[0])) <= 0:
                item = list(tbl)
                item.insert(0, Table.TableType)
                items.append(item)
        self._close_cursor(c)

        return sorted(items, key=cmp_to_key(lambda x, y: (x[1] > y[1]) - (x[1] < y[1])))

    def getVectorTables(self, schema=None):
        """ get list of table with a geometry column
                it returns:
                        name (table name)
                        namespace (schema)
                        type = 'view' (is a view?)
                        owner
                        tuples
                        pages
                        geometry_column:
                                f_geometry_column (or pg_attribute.attname, the geometry column name)
                                type (or pg_attribute.atttypid::regtype, the geometry column type name)
                                coord_dimension
                                srid
        """

        if not self.has_spatial:
            return []

        if schema:
            schema_where = u" AND nspname = %s " % self.quoteString(schema)
        else:
            schema_where = u" AND (nspname != 'information_schema' AND nspname !~ 'pg_') "

        geometry_column_from = u""
        geometry_fields_select = u"""att.attname,
                                                textin(regtypeout(att.atttypid::regtype)),
                                                NULL, NULL"""
        if self.has_geometry_columns and self.has_geometry_columns_access:
            geometry_column_from = u"""LEFT OUTER JOIN geometry_columns AS geo ON
                                                cla.relname = geo.f_table_name AND nsp.nspname = f_table_schema AND
                                                lower(att.attname) = lower(f_geometry_column)"""
            geometry_fields_select = u"""CASE WHEN geo.f_geometry_column IS NOT NULL THEN geo.f_geometry_column ELSE att.attname END,
                                                CASE WHEN geo.type IS NOT NULL THEN geo.type ELSE textin(regtypeout(att.atttypid::regtype)) END,
                                                geo.coord_dimension, geo.srid"""

        # discovery of all tables and whether they contain a geometry column
        sql = u"""SELECT
                                                cla.relname, nsp.nspname, cla.relkind,
                                                pg_get_userbyid(relowner), cla.reltuples, cla.relpages,
                                                pg_catalog.obj_description(cla.oid),
                                                """ + geometry_fields_select + """

                                        FROM pg_class AS cla
                                        JOIN pg_namespace AS nsp ON
                                                nsp.oid = cla.relnamespace

                                        JOIN pg_attribute AS att ON
                                                att.attrelid = cla.oid AND
                                                att.atttypid = 'geometry'::regtype OR
                                                att.atttypid IN (SELECT oid FROM pg_type WHERE typbasetype='geometry'::regtype )

                                        """ + geometry_column_from + """

                                        WHERE cla.relkind IN ('v', 'r', 'm', 'p') """ + schema_where + """
                                        ORDER BY nsp.nspname, cla.relname, att.attname"""

        items = []

        c = self._execute(None, sql)
        for i, tbl in enumerate(self._fetchall(c)):
            item = list(tbl)
            item.insert(0, Table.VectorType)
            items.append(item)
        self._close_cursor(c)

        return items

    def getRasterTables(self, schema=None):
        """ get list of table with a raster column
                it returns:
                        name (table name)
                        namespace (schema)
                        type = 'view' (is a view?)
                        owner
                        tuples
                        pages
                        raster_column:
                                r_raster_column (or pg_attribute.attname, the raster column name)
                                pixel type
                                block size
                                internal or external
                                srid
        """

        if not self.has_spatial:
            return []
        if not self.has_raster:
            return []

        if schema:
            schema_where = u" AND nspname = %s " % self.quoteString(schema)
        else:
            schema_where = u" AND (nspname != 'information_schema' AND nspname !~ 'pg_') "

        raster_column_from = u""
        raster_fields_select = u"""att.attname, NULL, NULL, NULL, NULL, NULL"""
        if self.has_raster_columns and self.has_raster_columns_access:
            raster_column_from = u"""LEFT OUTER JOIN raster_columns AS rast ON
                                                cla.relname = rast.r_table_name AND nsp.nspname = r_table_schema AND
                                                lower(att.attname) = lower(r_raster_column)"""
            raster_fields_select = u"""CASE WHEN rast.r_raster_column IS NOT NULL THEN rast.r_raster_column ELSE att.attname END,
                                                rast.pixel_types,
                                                rast.scale_x,
                                                rast.scale_y,
                                                rast.out_db,
                                                rast.srid"""

        # discovery of all tables and whether they contain a raster column
        sql = u"""SELECT
                                                cla.relname, nsp.nspname, cla.relkind,
                                                pg_get_userbyid(relowner), cla.reltuples, cla.relpages,
                                                pg_catalog.obj_description(cla.oid),
                                                """ + raster_fields_select + """

                                        FROM pg_class AS cla
                                        JOIN pg_namespace AS nsp ON
                                                nsp.oid = cla.relnamespace

                                        JOIN pg_attribute AS att ON
                                                att.attrelid = cla.oid AND
                                                att.atttypid = 'raster'::regtype OR
                                                att.atttypid IN (SELECT oid FROM pg_type WHERE typbasetype='raster'::regtype )

                                        """ + raster_column_from + """

                                        WHERE cla.relkind IN ('v', 'r', 'm', 'p') """ + schema_where + """
                                        ORDER BY nsp.nspname, cla.relname, att.attname"""

        items = []

        c = self._execute(None, sql)
        for i, tbl in enumerate(self._fetchall(c)):
            item = list(tbl)
            item.insert(0, Table.RasterType)
            items.append(item)
        self._close_cursor(c)

        return items

    def getTableRowCount(self, table):
        c = self._execute(None, u"SELECT COUNT(*) FROM %s" % self.quoteId(table))
        res = self._fetchone(c)[0]
        self._close_cursor(c)
        return res

    def getTableFields(self, table):
        """ return list of columns in table """

        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" AND nspname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT a.attnum AS ordinal_position,
                                a.attname AS column_name,
                                t.typname AS data_type,
                                a.attlen AS char_max_len,
                                a.atttypmod AS modifier,
                                a.attnotnull AS notnull,
                                a.atthasdef AS hasdefault,
                                adef.adsrc AS default_value,
                                pg_catalog.format_type(a.atttypid,a.atttypmod) AS formatted_type
                        FROM pg_class c
                        JOIN pg_attribute a ON a.attrelid = c.oid
                        JOIN pg_type t ON a.atttypid = t.oid
                        JOIN pg_namespace nsp ON c.relnamespace = nsp.oid
                        LEFT JOIN pg_attrdef adef ON adef.adrelid = a.attrelid AND adef.adnum = a.attnum
                        WHERE
                          a.attnum > 0 AND c.relname=%s %s
                        ORDER BY a.attnum""" % (self.quoteString(tablename), schema_where)

        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def getTableIndexes(self, table):
        """ get info about table's indexes. ignore primary key constraint index, they get listed in constraints """
        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" AND nspname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT idxcls.relname, indkey, indisunique = 't'
                                                FROM pg_index JOIN pg_class ON pg_index.indrelid=pg_class.oid
                                                JOIN pg_class AS idxcls ON pg_index.indexrelid=idxcls.oid
                                                JOIN pg_namespace nsp ON pg_class.relnamespace = nsp.oid
                                                        WHERE pg_class.relname=%s %s
                                                        AND indisprimary != 't' """ % (
            self.quoteString(tablename), schema_where)
        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def getTableConstraints(self, table):

        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" AND nspname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT c.conname, c.contype, c.condeferrable, c.condeferred, array_to_string(c.conkey, ' '), c.consrc,
                         t2.relname, c.confupdtype, c.confdeltype, c.confmatchtype, array_to_string(c.confkey, ' ') FROM pg_constraint c
                  LEFT JOIN pg_class t ON c.conrelid = t.oid
                        LEFT JOIN pg_class t2 ON c.confrelid = t2.oid
                        JOIN pg_namespace nsp ON t.relnamespace = nsp.oid
                        WHERE t.relname = %s %s """ % (self.quoteString(tablename), schema_where)

        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def getTableTriggers(self, table):

        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" AND nspname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT tgname, proname, tgtype, tgenabled NOT IN ('f', 'D')  FROM pg_trigger trig
                          LEFT JOIN pg_class t ON trig.tgrelid = t.oid
                                                        LEFT JOIN pg_proc p ON trig.tgfoid = p.oid
                                                        JOIN pg_namespace nsp ON t.relnamespace = nsp.oid
                                                        WHERE t.relname = %s %s """ % (
            self.quoteString(tablename), schema_where)

        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def enableAllTableTriggers(self, enable, table):
        """ enable or disable all triggers on table """
        self.enableTableTrigger(None, enable, table)

    def enableTableTrigger(self, trigger, enable, table):
        """ enable or disable one trigger on table """
        trigger = self.quoteId(trigger) if trigger is not None else "ALL"
        sql = u"ALTER TABLE %s %s TRIGGER %s" % (self.quoteId(table), "ENABLE" if enable else "DISABLE", trigger)
        self._execute_and_commit(sql)

    def deleteTableTrigger(self, trigger, table):
        """ delete trigger on table """
        sql = u"DROP TRIGGER %s ON %s" % (self.quoteId(trigger), self.quoteId(table))
        self._execute_and_commit(sql)

    def getTableRules(self, table):

        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" AND schemaname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT rulename, definition FROM pg_rules
                                        WHERE tablename=%s %s """ % (self.quoteString(tablename), schema_where)

        c = self._execute(None, sql)
        res = self._fetchall(c)
        self._close_cursor(c)
        return res

    def deleteTableRule(self, rule, table):
        """ delete rule on table """
        sql = u"DROP RULE %s ON %s" % (self.quoteId(rule), self.quoteId(table))
        self._execute_and_commit(sql)

    def getTableExtent(self, table, geom):
        """ find out table extent """
        subquery = u"SELECT st_extent(%s) AS extent FROM %s" % (self.quoteId(geom), self.quoteId(table))
        sql = u"SELECT st_xmin(extent), st_ymin(extent), st_xmax(extent), st_ymax(extent) FROM (%s) AS subquery" % subquery

        c = self._execute(None, sql)
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getTableEstimatedExtent(self, table, geom):
        """ find out estimated extent (from the statistics) """
        if self.isRasterTable(table):
            return

        schema, tablename = self.getSchemaTableName(table)
        schema_part = u"%s," % self.quoteString(schema) if schema is not None else ""

        subquery = u"SELECT st_estimated_extent(%s%s,%s) AS extent" % (
            schema_part, self.quoteString(tablename), self.quoteString(geom))
        sql = u"""SELECT st_xmin(extent), st_ymin(extent), st_xmax(extent), st_ymax(extent) FROM (%s) AS subquery """ % subquery

        try:
            c = self._execute(None, sql)
        except DbError:  # No statistics for the current table
            return
        res = self._fetchone(c)
        self._close_cursor(c)
        return res

    def getViewDefinition(self, view):
        """ returns definition of the view """

        schema, tablename = self.getSchemaTableName(view)
        schema_where = u" AND nspname=%s " % self.quoteString(schema) if schema is not None else ""

        sql = u"""SELECT pg_get_viewdef(c.oid) FROM pg_class c
                                                JOIN pg_namespace nsp ON c.relnamespace = nsp.oid
                        WHERE relname=%s %s AND (relkind='v' OR relkind='m') """ % (
            self.quoteString(tablename), schema_where)

        c = self._execute(None, sql)
        res = self._fetchone(c)
        self._close_cursor(c)
        return res[0] if res is not None else None

    def getSpatialRefInfo(self, srid):
        if not self.has_spatial:
            return

        try:
            c = self._execute(None, "SELECT srtext FROM spatial_ref_sys WHERE srid = '%d'" % srid)
        except DbError:
            return
        sr = self._fetchone(c)
        self._close_cursor(c)
        if sr is None:
            return

        srtext = sr[0]
        # try to extract just SR name (should be quoted in double quotes)
        regex = QRegExp('"([^"]+)"')
        if regex.indexIn(srtext) > -1:
            srtext = regex.cap(1)
        return srtext

    def isVectorTable(self, table):
        if self.has_geometry_columns and self.has_geometry_columns_access:
            schema, tablename = self.getSchemaTableName(table)
            sql = u"SELECT count(*) FROM geometry_columns WHERE f_table_schema = %s AND f_table_name = %s" % (
                self.quoteString(schema), self.quoteString(tablename))

            c = self._execute(None, sql)
            res = self._fetchone(c)
            self._close_cursor(c)
            return res is not None and res[0] > 0

        return False

    def isRasterTable(self, table):
        if self.has_raster_columns and self.has_raster_columns_access:
            schema, tablename = self.getSchemaTableName(table)
            sql = u"SELECT count(*) FROM raster_columns WHERE r_table_schema = %s AND r_table_name = %s" % (
                self.quoteString(schema), self.quoteString(tablename))

            c = self._execute(None, sql)
            res = self._fetchone(c)
            self._close_cursor(c)
            return res is not None and res[0] > 0

        return False

    def createTable(self, table, field_defs, pkey):
        """ create ordinary table
                        'fields' is array containing field definitions
                        'pkey' is the primary key name
        """
        if len(field_defs) == 0:
            return False

        sql = "CREATE TABLE %s (" % self.quoteId(table)
        sql += u", ".join(field_defs)
        if pkey is not None and pkey != "":
            sql += u", PRIMARY KEY (%s)" % self.quoteId(pkey)
        sql += ")"

        self._execute_and_commit(sql)
        return True

    def deleteTable(self, table):
        """ delete table and its reference in either geometry_columns or raster_columns """
        schema, tablename = self.getSchemaTableName(table)
        schema_part = u"%s, " % self.quoteString(schema) if schema is not None else ""
        if self.isVectorTable(table):
            sql = u"SELECT DropGeometryTable(%s%s)" % (schema_part, self.quoteString(tablename))
        elif self.isRasterTable(table):
            # Fix #8521: delete raster table and references from raster_columns table
            sql = u"DROP TABLE %s" % self.quoteId(table)
        else:
            sql = u"DROP TABLE %s" % self.quoteId(table)
        self._execute_and_commit(sql)

    def emptyTable(self, table):
        """ delete all rows from table """
        sql = u"TRUNCATE %s" % self.quoteId(table)
        self._execute_and_commit(sql)

    def renameTable(self, table, new_table):
        """ rename a table in database """
        schema, tablename = self.getSchemaTableName(table)
        if new_table == tablename:
            return

        c = self._get_cursor()

        sql = u"ALTER TABLE %s RENAME TO %s" % (self.quoteId(table), self.quoteId(new_table))
        self._execute(c, sql)

        # update geometry_columns if PostGIS is enabled
        if self.has_geometry_columns and not self.is_geometry_columns_view:
            schema_where = u" AND f_table_schema=%s " % self.quoteString(schema) if schema is not None else ""
            sql = u"UPDATE geometry_columns SET f_table_name=%s WHERE f_table_name=%s %s" % (
                self.quoteString(new_table), self.quoteString(tablename), schema_where)
            self._execute(c, sql)

        self._commit()

    def commentTable(self, schema, tablename, comment, db):
        db.connector._execute(None, 'COMMENT ON TABLE "{0}"."{1}" IS E\'{2}\';'.format(schema, tablename, comment))

    def unCommentTable(self, schema, tablename, db):
        db.connector._execute(None, 'COMMENT ON TABLE "{0}"."{1}" IS NULL;'.format(schema, tablename))

    def getComment(self, tab, field, db):
        """Returns the comment for a field"""
        # SQL Query checking if a comment exists for the field
        sql_cpt = "Select count(*) from pg_description pd, pg_class pc, pg_attribute pa where relname = '%s' and attname = '%s' and pa.attrelid = pc.oid and pd.objoid = pc.oid and pd.objsubid = pa.attnum" % (tab, field)
        # SQL Query that return the comment of the field
        sql = "Select pd.description from pg_description pd, pg_class pc, pg_attribute pa where relname = '%s' and attname = '%s' and pa.attrelid = pc.oid and pd.objoid = pc.oid and pd.objsubid = pa.attnum" % (tab, field)
        c = db.connector._execute(None, sql_cpt) # Execute Check query
        res = db.connector._fetchone(c)[0] # Store result
        if res == 1:
            # When a comment exists
            c = db.connector._execute(None, sql) # Execute query
            res = db.connector._fetchone(c)[0] # Store result
            db.connector._close_cursor(c) # Close cursor
            return res # Return comment
        else:
            return ''

    def moveTableToSchema(self, table, new_schema):
        schema, tablename = self.getSchemaTableName(table)
        if new_schema == schema:
            return

        c = self._get_cursor()

        sql = u"ALTER TABLE %s SET SCHEMA %s" % (self.quoteId(table), self.quoteId(new_schema))
        self._execute(c, sql)

        # update geometry_columns if PostGIS is enabled
        if self.has_geometry_columns and not self.is_geometry_columns_view:
            schema, tablename = self.getSchemaTableName(table)
            schema_where = u" AND f_table_schema=%s " % self.quoteString(schema) if schema is not None else ""
            sql = u"UPDATE geometry_columns SET f_table_schema=%s WHERE f_table_name=%s %s" % (
                self.quoteString(new_schema), self.quoteString(tablename), schema_where)
            self._execute(c, sql)

        self._commit()

    def moveTable(self, table, new_table, new_schema=None):
        schema, tablename = self.getSchemaTableName(table)
        if new_schema == schema and new_table == tablename:
            return
        if new_schema == schema:
            return self.renameTable(table, new_table)
        if new_table == table:
            return self.moveTableToSchema(table, new_schema)

        c = self._get_cursor()
        t = u"__new_table__"

        sql = u"ALTER TABLE %s RENAME TO %s" % (self.quoteId(table), self.quoteId(t))
        self._execute(c, sql)

        sql = u"ALTER TABLE %s SET SCHEMA %s" % (self.quoteId((schema, t)), self.quoteId(new_schema))
        self._execute(c, sql)

        sql = u"ALTER TABLE %s RENAME TO %s" % (self.quoteId((new_schema, t)), self.quoteId(table))
        self._execute(c, sql)

        # update geometry_columns if PostGIS is enabled
        if self.has_geometry_columns and not self.is_geometry_columns_view:
            schema, tablename = self.getSchemaTableName(table)
            schema_where = u" f_table_schema=%s AND " % self.quoteString(schema) if schema is not None else ""
            schema_part = u" f_table_schema=%s, " % self.quoteString(new_schema) if schema is not None else ""
            sql = u"UPDATE geometry_columns SET %s f_table_name=%s WHERE %s f_table_name=%s" % (
                schema_part, self.quoteString(new_table), schema_where, self.quoteString(tablename))
            self._execute(c, sql)

        self._commit()

    def createView(self, view, query):
        sql = u"CREATE VIEW %s AS %s" % (self.quoteId(view), query)
        self._execute_and_commit(sql)

    def createSpatialView(self, view, query):
        self.createView(view, query)

    def deleteView(self, view, isMaterialized=False):
        sql = u"DROP %s VIEW %s" % ('MATERIALIZED' if isMaterialized else '', self.quoteId(view))
        self._execute_and_commit(sql)

    def renameView(self, view, new_name):
        """ rename view in database """
        self.renameTable(view, new_name)

    def createSchema(self, schema):
        """ create a new empty schema in database """
        sql = u"CREATE SCHEMA %s" % self.quoteId(schema)
        self._execute_and_commit(sql)

    def deleteSchema(self, schema):
        """ drop (empty) schema from database """
        sql = u"DROP SCHEMA %s" % self.quoteId(schema)
        self._execute_and_commit(sql)

    def renameSchema(self, schema, new_schema):
        """ rename a schema in database """
        sql = u"ALTER SCHEMA %s RENAME TO %s" % (self.quoteId(schema), self.quoteId(new_schema))
        self._execute_and_commit(sql)

    def runVacuum(self):
        """ run vacuum on the db """
        self._execute_and_commit("VACUUM")

    def runVacuumAnalyze(self, table):
        """ run vacuum analyze on a table """
        sql = u"VACUUM ANALYZE %s" % self.quoteId(table)
        self._execute(None, sql)
        self._commit()

    def runRefreshMaterializedView(self, table):
        """ run refresh materialized view on a table """
        sql = u"REFRESH MATERIALIZED VIEW %s" % self.quoteId(table)
        self._execute(None, sql)
        self._commit()

    def addTableColumn(self, table, field_def):
        """ add a column to table """
        sql = u"ALTER TABLE %s ADD %s" % (self.quoteId(table), field_def)
        self._execute_and_commit(sql)

    def deleteTableColumn(self, table, column):
        """ delete column from a table """
        if self.isGeometryColumn(table, column):
            # use PostGIS function to delete geometry column correctly
            schema, tablename = self.getSchemaTableName(table)
            schema_part = u"%s, " % self.quoteString(schema) if schema else ""
            sql = u"SELECT DropGeometryColumn(%s%s, %s)" % (
                schema_part, self.quoteString(tablename), self.quoteString(column))
        else:
            sql = u"ALTER TABLE %s DROP %s" % (self.quoteId(table), self.quoteId(column))
        self._execute_and_commit(sql)

    def updateTableColumn(self, table, column, new_name=None, data_type=None, not_null=None, default=None, comment=None, test=None):
        if new_name is None and data_type is None and not_null is None and default is None and comment is None:
            return

        c = self._get_cursor()

        # update column definition
        col_actions = []
        if data_type is not None:
            col_actions.append(u"TYPE %s" % data_type)
        if not_null is not None:
            col_actions.append(u"SET NOT NULL" if not_null else u"DROP NOT NULL")
        if default is not None:
            if default and default != '':
                col_actions.append(u"SET DEFAULT %s" % default)
            else:
                col_actions.append(u"DROP DEFAULT")
        if len(col_actions) > 0:
            sql = u"ALTER TABLE %s" % self.quoteId(table)
            alter_col_str = u"ALTER %s" % self.quoteId(column)
            for a in col_actions:
                sql += u" %s %s," % (alter_col_str, a)
            self._execute(c, sql[:-1])

        # rename the column
        if new_name is not None and new_name != column:
            sql = u"ALTER TABLE %s RENAME %s TO %s" % (
                self.quoteId(table), self.quoteId(column), self.quoteId(new_name))
            self._execute(c, sql)

            # update geometry_columns if PostGIS is enabled
            if self.has_geometry_columns and not self.is_geometry_columns_view:
                schema, tablename = self.getSchemaTableName(table)
                schema_where = u" f_table_schema=%s AND " % self.quoteString(schema) if schema is not None else ""
                sql = u"UPDATE geometry_columns SET f_geometry_column=%s WHERE %s f_table_name=%s AND f_geometry_column=%s" % (
                    self.quoteString(new_name), schema_where, self.quoteString(tablename), self.quoteString(column))
                self._execute(c, sql)

        # comment the column
        if comment is not None:
            schema, tablename = self.getSchemaTableName(table)
            sql = u"COMMENT ON COLUMN %s.%s.%s is '%s'" % (schema, tablename, column, comment)
            self._execute(c, sql)

        self._commit()

    def renameTableColumn(self, table, column, new_name):
        """ rename column in a table """
        return self.updateTableColumn(table, column, new_name)

    def setTableColumnType(self, table, column, data_type):
        """ change column type """
        return self.updateTableColumn(table, column, None, data_type)

    def setTableColumnNull(self, table, column, is_null):
        """ change whether column can contain null values """
        return self.updateTableColumn(table, column, None, None, not is_null)

    def setTableColumnDefault(self, table, column, default):
        """ change column's default value.
                If default=None or an empty string drop default value """
        return self.updateTableColumn(table, column, None, None, None, default)

    def isGeometryColumn(self, table, column):

        schema, tablename = self.getSchemaTableName(table)
        schema_where = u" f_table_schema=%s AND " % self.quoteString(schema) if schema is not None else ""

        sql = u"SELECT count(*) > 0 FROM geometry_columns WHERE %s f_table_name=%s AND f_geometry_column=%s" % (
            schema_where, self.quoteString(tablename), self.quoteString(column))

        c = self._execute(None, sql)
        res = self._fetchone(c)[0] == 't'
        self._close_cursor(c)
        return res

    def addGeometryColumn(self, table, geom_column='geom', geom_type='POINT', srid=-1, dim=2):
        schema, tablename = self.getSchemaTableName(table)
        schema_part = u"%s, " % self.quoteString(schema) if schema else ""

        sql = u"SELECT AddGeometryColumn(%s%s, %s, %d, %s, %d)" % (
            schema_part, self.quoteString(tablename), self.quoteString(geom_column), srid, self.quoteString(geom_type), dim)
        self._execute_and_commit(sql)

    def deleteGeometryColumn(self, table, geom_column):
        return self.deleteTableColumn(table, geom_column)

    def addTableUniqueConstraint(self, table, column):
        """ add a unique constraint to a table """
        sql = u"ALTER TABLE %s ADD UNIQUE (%s)" % (self.quoteId(table), self.quoteId(column))
        self._execute_and_commit(sql)

    def deleteTableConstraint(self, table, constraint):
        """ delete constraint in a table """
        sql = u"ALTER TABLE %s DROP CONSTRAINT %s" % (self.quoteId(table), self.quoteId(constraint))
        self._execute_and_commit(sql)

    def addTablePrimaryKey(self, table, column):
        """ add a primery key (with one column) to a table """
        sql = u"ALTER TABLE %s ADD PRIMARY KEY (%s)" % (self.quoteId(table), self.quoteId(column))
        self._execute_and_commit(sql)

    def createTableIndex(self, table, name, column):
        """ create index on one column using default options """
        sql = u"CREATE INDEX %s ON %s (%s)" % (self.quoteId(name), self.quoteId(table), self.quoteId(column))
        self._execute_and_commit(sql)

    def deleteTableIndex(self, table, name):
        schema, tablename = self.getSchemaTableName(table)
        sql = u"DROP INDEX %s" % self.quoteId((schema, name))
        self._execute_and_commit(sql)

    def createSpatialIndex(self, table, geom_column='geom'):
        schema, tablename = self.getSchemaTableName(table)
        idx_name = self.quoteId(u"sidx_%s_%s" % (tablename, geom_column))
        sql = u"CREATE INDEX %s ON %s USING GIST(%s)" % (idx_name, self.quoteId(table), self.quoteId(geom_column))
        self._execute_and_commit(sql)

    def deleteSpatialIndex(self, table, geom_column='geom'):
        schema, tablename = self.getSchemaTableName(table)
        idx_name = self.quoteId(u"sidx_%s_%s" % (tablename, geom_column))
        return self.deleteTableIndex(table, idx_name)

    def execution_error_types(self):
        return psycopg2.Error, psycopg2.ProgrammingError, psycopg2.Warning

    def connection_error_types(self):
        return psycopg2.InterfaceError, psycopg2.OperationalError

    # moved into the parent class: DbConnector._execute()
    # def _execute(self, cursor, sql):
    #       pass

    # moved into the parent class: DbConnector._execute_and_commit()
    # def _execute_and_commit(self, sql):
    #       pass

    # moved into the parent class: DbConnector._get_cursor()
    # def _get_cursor(self, name=None):
    #       pass

    # moved into the parent class: DbConnector._fetchall()
    # def _fetchall(self, c):
    #       pass

    # moved into the parent class: DbConnector._fetchone()
    # def _fetchone(self, c):
    #       pass

    # moved into the parent class: DbConnector._commit()
    # def _commit(self):
    #       pass

    # moved into the parent class: DbConnector._rollback()
    # def _rollback(self):
    #       pass

    # moved into the parent class: DbConnector._get_cursor_columns()
    # def _get_cursor_columns(self, c):
    #       pass

    def getSqlDictionary(self):
        from .sql_dictionary import getSqlDictionary

        sql_dict = getSqlDictionary()

        # get schemas, tables and field names
        items = []
        sql = u"""SELECT nspname FROM pg_namespace WHERE nspname !~ '^pg_' AND nspname != 'information_schema'
UNION SELECT relname FROM pg_class WHERE relkind IN ('v', 'r', 'm', 'p')
UNION SELECT attname FROM pg_attribute WHERE attnum > 0"""
        c = self._execute(None, sql)
        for row in self._fetchall(c):
            items.append(row[0])
        self._close_cursor(c)

        sql_dict["identifier"] = items
        return sql_dict

    def getQueryBuilderDictionary(self):
        from .sql_dictionary import getQueryBuilderDictionary

        return getQueryBuilderDictionary()