Quick and dirty patch to DB-Manager after PR 8831

The "comments" PR 8831 added support for postgres only
(and broke all the others backends).

I'd be in favor of a revert of the whole original PR but
this patch restores functionality and could be an acceptable
temporary fix until the comments PR is reworked in a more
maintainable and elegant way.

Fixes #21151 btw

python/plugins/db_manager/db_plugins/gpkg/plugin.py

@@ -301,6 +301,10 @@ def __init__(self, row, table):
         self.num, self.name, self.dataType, self.notNull, self.default, self.primaryKey = row
         self.hasDefault = self.default
 
+    def getComment(self):
+        """Returns the comment for a field"""
+        return ''
+
 
 class GPKGTableIndex(TableIndex):
 

python/plugins/db_manager/db_plugins/oracle/plugin.py

@@ -557,6 +557,10 @@ def update(self, new_name, new_type_str=None, new_not_null=None,
             self.table().refreshIndexes()
         return ret
 
+    def getComment(self):
+        """Returns the comment for a field"""
+        return ''
+
 
 class ORTableConstraint(TableConstraint):
 

python/plugins/db_manager/db_plugins/spatialite/plugin.py

@@ -294,6 +294,10 @@ def __init__(self, row, table):
         self.num, self.name, self.dataType, self.notNull, self.default, self.primaryKey = row
         self.hasDefault = self.default
 
+    def getComment(self):
+        """Returns the comment for a field"""
+        return ''
+
 
 class SLTableIndex(TableIndex):
 

python/plugins/db_manager/db_plugins/vlayers/plugin.py

@@ -192,3 +192,7 @@ def __init__(self, row, table):
         TableField.__init__(self, table)
         self.num, self.name, self.dataType, self.notNull, self.default, self.primaryKey = row
         self.hasDefault = self.default
+
+    def getComment(self):
+        """Returns the comment for a field"""
+        return ''

python/plugins/db_manager/dlg_field_properties.py

@@ -56,18 +56,23 @@ def setField(self, fld):
         self.chkNull.setChecked(not fld.notNull)
         if fld.hasDefault:
             self.editDefault.setText(fld.default)
-        # Check with SQL query 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" % (self.table.name, self.editName.text())
-        # Get the comment for the field with SQL Query
-        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" % (self.table.name, self.editName.text())
-        c = self.db.connector._execute(None, sql_cpt) # Execute check query
-        res = self.db.connector._fetchone(c)[0] # Fetch data
-        # Check if result is 1 then it's ok, else we don't want to get a value
-        if res == 1:
-            c = self.db.connector._execute(None, sql) # Execute query returning the comment value
-            res = self.db.connector._fetchone(c)[0] # Fetch the comment value
-            self.db.connector._close_cursor(c) # Close cursor
-            self.editCom.setText(res) # Set comment value
+        # This is an ugly patch, but the comments PR https://github.com/qgis/QGIS/pull/8831 added
+        # support for postgres only and broke all the others :(
+        try:
+            # Check with SQL query 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" % (self.table.name, self.editName.text())
+            # Get the comment for the field with SQL Query
+            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" % (self.table.name, self.editName.text())
+            c = self.db.connector._execute(None, sql_cpt) # Execute check query
+            res = self.db.connector._fetchone(c)[0] # Fetch data
+            # Check if result is 1 then it's ok, else we don't want to get a value
+            if res == 1:
+                c = self.db.connector._execute(None, sql) # Execute query returning the comment value
+                res = self.db.connector._fetchone(c)[0] # Fetch the comment value
+                self.db.connector._close_cursor(c) # Close cursor
+                self.editCom.setText(res) # Set comment value
+        except:
+            self.editCom.setEnabled(False)
 
     def getField(self, newCopy=False):
         fld = TableField(self.table) if not self.fld or newCopy else self.fld

python/plugins/db_manager/dlg_table_properties.py

@@ -29,7 +29,7 @@
 from qgis.utils import OverrideCursor
 
 from .db_plugins.data_model import TableFieldsModel, TableConstraintsModel, TableIndexesModel
-from .db_plugins.plugin import BaseError
+from .db_plugins.plugin import BaseError, DbError
 from .dlg_db_error import DlgDbError
 
 from .dlg_field_properties import DlgFieldProperties
@@ -333,25 +333,37 @@ def deleteIndex(self):
                 DlgDbError.showError(e, self)
 
     def createComment(self):
-        #Function that add a comment to the selected table
+        """Adds a comment to the selected table"""
+
         try:
             #Using the db connector, executing de SQL query Comment on table
             self.db.connector._execute(None, 'COMMENT ON TABLE "{0}"."{1}" IS E\'{2}\';'.format(self.table.schema().name, self.table.name, self.viewComment.text()))
         except DbError as e:
             DlgDbError.showError(e, self)
             return
+        except Exception as e:
+            # This is an ugly patch, but the comments PR https://github.com/qgis/QGIS/pull/8831 added
+            # support for postgres only and broke all the others :(
+            QMessageBox.information(self, self.tr("Add comment"), self.tr("Comments are not supported for this database."))
+            return
         self.refresh()
         #Display successful message
         QMessageBox.information(self, self.tr("Add comment"), self.tr("Table successfully commented"))
 
     def deleteComment(self):
-        #Function that drop the comment to the selected table
+        """Drops the comment on the selected table"""
+
         try:
             #Using the db connector, executing de SQL query Comment on table using the NULL definition
             self.db.connector._execute(None, 'COMMENT ON TABLE "{0}"."{1}" IS NULL;'.format(self.table.schema().name, self.table.name))
         except DbError as e:
             DlgDbError.showError(e, self)
             return
+        except Exception as e:
+            # This is an ugly patch, but the comments PR https://github.com/qgis/QGIS/pull/8831 added
+            # support for postgres only and broke all the others :(
+            QMessageBox.information(self, self.tr("Add comment"), self.tr("Comments are not supported for this database."))
+            return
         self.refresh()
         #Refresh line edit, put a void comment
         self.viewComment.setText('')