lazarus-ccr/components/tvplanit/source/addons/zeos/vpzeosds.pas

{$I vp.inc}

unit VpZeosDs;

interface

uses
  SysUtils, Classes, DB,
  VpData, VpBaseDS, VpDBDS,
  ZCompatibility, ZConnection, ZDataset;

type
  
  { TVpZeosDatastore }
  
  TVpZeosDatastore = class(TVpCustomDBDatastore)
  private
    FConnection: TZConnection;
    FContactsTable: TZTable;
    FEventsTable: TZTable;
    FResourceTable: TZTable;
    FTasksTable: TZTable;
    procedure CreateAutoInc_Firebird(ATableName, AIdFieldName: String);
    procedure SetConnection(const AValue: TZConnection);
    
  protected
    procedure CreateTable(const ATableName: String; CreateIndex: Boolean = true);
    procedure CreateAllTables;
    function GetContactsTable: TDataset; override;
    function GetEventsTable: TDataset; override;
    function GetResourceTable: TDataset; override;
    function GetTasksTable: TDataset; override;
    procedure InternalPurgeContacts(Res: TVpResource); override;
    procedure InternalPurgeEvents(Res: TVpResource); override;
    procedure InternalPurgeTasks(Res: TVpResource); override;
    procedure Loaded; override;
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
    procedure SetConnected(const AValue: Boolean); override;
    procedure SetTableConnections(AConnection: TZConnection);
    function TableExists(ATableName: String): Boolean;
    function TablesExist: boolean;

  protected
    FIdFieldTypeNameInSQL: String;
    FBoolFieldTypeNameInSQL: String;
    procedure AdjustSQLFieldTypeNames; virtual;
    
  protected
    // Fix old tables
    procedure AddField(ATableName, AFieldName: String; AFieldType: TFieldType;
      ASize: Integer=0);
    procedure RenameFields(ATableName: String; AFields: TStrings);
    procedure FixContactsTable;

  public
    constructor Create(AOwner: TComponent); override;
    procedure CreateTables;
    function GetNextID({%H-}TableName: string): integer; override;

    property ResourceTable;
    property EventsTable;
    property ContactsTable;
    property TasksTable;

  published
    property Connection: TZConnection read FConnection write SetConnection;

    // inherited
    property AutoConnect default false;
    property AutoCreate default false;
    property Daybuffer;
  end;


implementation

uses
  LazFileUtils, ZAbstractDataset,
  VpConst, VpException;

{ TVpZeosDatastore }

constructor TVpZeosDatastore.Create(AOwner: TComponent);
begin
  inherited;
  FAutoCreate := false;

  FContactsTable := TZTable.Create(self);
  FContactsTable.TableName := ContactsTableName;
  FContactsTable.UpdateMode := umUpdateAll;

  FEventsTable := TZTable.Create(Self);
  FEventsTable.TableName := EventsTableName;
  FEventsTable.UpdateMode := umUpdateAll;

  FResourceTable := TZTable.Create(self);
  FResourceTable.TableName := ResourceTableName;
  FResourceTable.UpdateMode := umUpdateAll;

  FTasksTable := TZTable.Create(self);
  FTasksTable.TableName := TasksTableName;
  FTasksTable.UpdateMode := umUpdateAll;
end;

procedure TVpZeosDatastore.AddField(ATableName, AFieldName: String;
  AFieldType: TFieldType; ASize: Integer=0);
var
  ft: String;
  sql: String;
begin
  if AFieldType = ftInteger then
    ft := 'INTEGER' else
  if (AFieldType = ftString) then
    ft := 'VARCHAR(' + intToStr(ASize) + ')'
  else
    raise Exception.Create('Field type not supported here.');
  sql := Format('ALTER TABLE %s ADD COLUMN %s %s;', [ATablename, AFieldName, ft]);
  FConnection.ExecuteDirect(sql);
end;

{ Select the correct SQL field type names which vary between SQL dialects. }
procedure TVpZeosDatastore.AdjustSQLFieldTypeNames;
var
  protocol: String;
begin
  FIdFieldTypeNameInSQL := 'INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT';
  FBoolFieldTypeNameInSQL := 'BOOL';
 
  if Assigned(FConnection) then
  begin
    protocol := Lowercase(FConnection.Protocol);
    if protocol = 'firebird' then
    begin
//      FIdFieldTypeNameInSQL := 'INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY';    // This can be used in Firebird v3 to replace the trigger and generator
      FIdFieldTypeNameInSQL := 'INTEGER NOT NULL PRIMARY KEY';    // This works for firebird v2.x and v3 when triggers & generators are provided
      FBoolFieldTypenameInSQL := 'BOOLEAN';
    end else
    if pos('postgres', protocol) > 0 then
      FIdFieldTypeNameInSQL := 'SERIAL NOT NULL PRIMARY KEY'
    else 
    if protocol = 'sqlite' then
      FIdFieldTypeNameInSQL := 'INTEGER PRIMARY KEY'
    else 
    if protocol = 'mssql' then
    begin
      FIdFieldTypeNameInSQL := 'INTEGER NOT NULL IDENTITY PRIMARY KEY';
      FBoolFieldTypeNameInSQL := 'BIT';
    end else
    if protocol = 'mysql' then
      FBoolFieldTypeNameInSQL := 'BIT';
  end;
end;

procedure TVpZeosDatastore.CreateAllTables;
var
  wasConnected: Boolean;
begin
  wasConnected := FConnection.Connected;
  try
    if FContactsTable.Connection = nil then begin
      FConnection.Connected := false;
      SetTableConnections(FConnection);
    end;
    FConnection.Connected := true;
    if not TableExists(ContactsTableName) then CreateTable(ContactsTableName);
    if not TableExists(EventsTableName) then CreateTable(EventsTableName);
    if not TableExists(ResourceTableName) then CreateTable(ResourceTableName);
    if not TableExists(TasksTableName) then CreateTable(TasksTableName);
  finally
    FConnection.Connected := wasConnected;
  end;
end;

{ Create generator and trigger for Firebird in order to autoincrement the values
  in field AIdFieldName of table ATableName.
  http://firebirdfaq.org/faq29/ }
procedure TVpZeosDatastore.CreateAutoInc_Firebird(ATableName, AIdFieldName: String);
begin
  FConnection.ExecuteDirect(Format(
    'CREATE GENERATOR gen_%s_id;', [ATableName]
  ));
  FConnection.ExecuteDirect(Format(
    'SET GENERATOR gen_%s_id TO 0;', [ATableName]
  ));
  FConnection.ExecuteDirect(Format(
    'CREATE TRIGGER %0:s_BI FOR %0:s ' +
    'ACTIVE BEFORE INSERT POSITION 0 ' +
    'AS ' +
    'BEGIN ' +
    'if (NEW.%1:s is NULL) then NEW.%1:s = GEN_ID(GEN_%0:s_ID, 1); ' +
    'END', [ATableName, AIdFieldName]
  ));
end;

procedure TVpZeosDatastore.CreateTable(const ATableName: String;
  CreateIndex: Boolean = true);
var
  CREATE_TABLE: String;
begin
  if (Lowercase(FConnection.Protocol) = 'firebird') then
    CREATE_TABLE := 'RECREATE TABLE '  // Not clear if this is correct for firebird v2.x, it is for fb v3
  else
    CREATE_TABLE := 'CREATE TABLE ';

  if ATableName = ContactsTableName then begin
    FConnection.ExecuteDirect(
      CREATE_TABLE + 'Contacts ('+
        'RecordID ' + FIDFieldTypeNameInSQL + ', '+
        'ResourceID INTEGER, '+
        'FirstName VARCHAR(50), '+
        'LastName VARCHAR(50), '+
        'Title VARCHAR(20) ,'+
        'Category INTEGER, '+
        'Birthdate DATE, '+
        'Anniversary DATE, '+
        'Company VARCHAR(50), '+
        'Department VARCHAR(50), '+
        'Job_Position VARCHAR(30), '+
        'AddressType1 INTEGER, '+
        'Address1 VARCHAR(100), '+
        'City1 VARCHAR(50), '+
        'State1 VARCHAR(25), '+
        'Zip1 VARCHAR(10), '+
        'Country1 VARCHAR(25), '+
        'AddressType2 INTEGER, '+
        'Address2 VARCHAR(100), '+
        'City2 VARCHAR(50), '+
        'State2 VARCHAR(25), '+
        'Zip2 VARCHAR(10), '+
        'Country2 VARCHAR(25), '+
        'Notes VARCHAR(1024), '+
        'EMail1 VARCHAR(100), '+
        'EMail2 VARCHAR(100), '+
        'EMail3 VARCHAR(100), '+
        'EMailType1 INTEGER, '+
        'EMailType2 INTEGER, '+
        'EMailType3 INTEGER, '+
        'Phone1 VARCHAR(25), '+
        'Phone2 VARCHAR(25), '+
        'Phone3 VARCHAR(25), '+
        'Phone4 VARCHAR(25), '+
        'Phone5 VARCHAR(25), '+
        'PhoneType1 INTEGER, '+
        'PhoneType2 INTEGER, '+
        'PhoneType3 INTEGER, '+
        'PhoneType4 INTEGER, '+
        'PhoneType5 INTEGER, '+
        'Website1 VARCHAR(100), '+
        'Website2 VARCHAR(100), '+
        'WebsiteType1 INTEGER, '+
        'WebsiteType2 INTEGER, '+
        'Custom1 VARCHAR(100), '+
        'Custom2 VARCHAR(100),'+
        'Custom3 VARCHAR(100), '+
        'Custom4 VARCHAR(100), '+
        'UserField0 VARCHAR(100), '+
        'UserField1 VARCHAR(100), '+
        'UserField2 VARCHAR(100), '+
        'UserField3 VARCHAR(100), '+
        'UserField4 VARCHAR(100), '+
        'UserField5 VARCHAR(100), '+
        'UserField6 VARCHAR(100), '+
        'UserField7 VARCHAR(100), '+
        'UserField8 VARCHAR(100), '+
        'UserField9 VARCHAR(100) )'
    );
    if CreateIndex then begin
      FConnection.ExecuteDirect(
        'CREATE INDEX ContactsResourceID_idx ON Contacts(ResourceID)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX ContactsName_idx ON Contacts(LastName, FirstName)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX ContactsCompany_idx ON Contacts(Company)'
      );
    end;
    if Lowercase(FConnection.Protocol) = 'firebird' then
      CreateAutoInc_Firebird('Contacts', 'RecordID');
  end else
  if ATableName = EventsTableName then begin
    FConnection.ExecuteDirect(
      CREATE_TABLE + 'Events ('+
        'RecordID ' + FIdFieldTypeNameInSQL + ', '+
        'StartTime TIMESTAMP, '+
        'EndTime TIMESTAMP, '+
        'ResourceID INTEGER, '+
        'Description VARCHAR(255), '+
        'Location VARCHAR(255), '+
        'Notes VARCHAR(1024), ' +
        'Category INTEGER, '+
        'AllDayEvent ' + FBoolFieldTypeNameInSQL + ', '+
        'DingPath VARCHAR(255), '+
        'AlarmSet ' + FBoolFieldTypeNameInSQL + ', '+
        'AlarmAdvance INTEGER, '+
        'AlarmAdvanceType INTEGER, '+
        'SnoozeTime TIMESTAMP, '+
        'RepeatCode INTEGER, '+
        'RepeatRangeEnd TIMESTAMP, '+
        'CustomInterval INTEGER, '+
        'UserField0 VARCHAR(100), '+
        'UserField1 VARCHAR(100), '+
        'UserField2 VARCHAR(100), '+
        'UserField3 VARCHAR(100), '+
        'UserField4 VARCHAR(100), '+
        'UserField5 VARCHAR(100), '+
        'UserField6 VARCHAR(100), '+
        'UserField7 VARCHAR(100), '+
        'UserField8 VARCHAR(100), '+
        'UserField9 VARCHAR(100) )'
    );
    if CreateIndex then begin
      FConnection.ExecuteDirect(
        'CREATE INDEX EventsResourceID_idx ON Events(ResourceID)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX EventsStartTime_idx ON Events(StartTime)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX EventsEndTime_idx ON Events(EndTime)'
      );
    end;
    if Lowercase(FConnection.Protocol) = 'firebird' then
      CreateAutoInc_Firebird('Events', 'RecordID');
  end else
  if ATableName = ResourceTableName then begin
    FConnection.ExecuteDirect(
      CREATE_TABLE + 'Resources ( '+
         'ResourceID ' + FIdFieldTypeNameInSQL + ', '+
         'Description VARCHAR(255), '+
         'Notes VARCHAR(1024), '+
         'ImageIndex INTEGER, '+
         'ResourceActive ' + FBoolFieldTypeNameInSQL + ', '+
         'UserField0 VARCHAR(100), '+
         'UserField1 VARCHAR(100), '+
         'UserField2 VARCHAR(100), '+
         'UserField3 VARCHAR(100), '+
         'UserField4 VARCHAR(100), '+
         'UserField5 VARCHAR(100), '+
         'UserField6 VARCHAR(100), '+
         'UserField7 VARCHAR(100), '+
         'UserField8 VARCHAR(100), '+
         'UserField9 VARCHAR(100) )'
    );
    if Lowercase(FConnection.Protocol) = 'firebird' then
      CreateAutoInc_Firebird('Resources', 'ResourceID');
  end else
  if ATableName = TasksTableName then begin
    FConnection.ExecuteDirect(
      CREATE_TABLE + 'Tasks ('+
        'RecordID ' + FIdFieldTypeNameInSQL + ', '+
        'ResourceID INTEGER, '+
        'Complete ' + FBoolFieldTypeNameInSQL + ', '+
        'Description VARCHAR(255), '+
        'Details VARCHAR(1024), '+
        'CreatedOn TIMESTAMP, '+
        'Priority INTEGER, '+
        'Category INTEGER, '+
        'CompletedOn TIMESTAMP, '+
        'DueDate TIMESTAMP, '+
        'UserField0 VARCHAR(100), '+
        'UserField1 VARCHAR(100), '+
        'UserField2 VARCHAR(100), '+
        'UserField3 VARCHAR(100), '+
        'UserField4 VARCHAR(100), '+
        'UserField5 VARCHAR(100), '+
        'UserField6 VARCHAR(100), '+
        'UserField7 VARCHAR(100), '+
        'UserField8 VARCHAR(100), '+
        'UserField9 VARCHAR(100) )'
    );
    if CreateIndex then begin
      FConnection.ExecuteDirect(
        'CREATE INDEX TasksResourceID_idx ON Tasks(ResourceID)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX TasksDueDate_idx ON Tasks(DueDate)'
      );
      FConnection.ExecuteDirect(
        'CREATE INDEX TasksCompletedOn_idx ON Tasks(CompletedOn)'
      );
      if Lowercase(FConnection.Protocol) = 'firebird' then
        CreateAutoInc_Firebird('Tasks', 'RecordID');
    end;
  end;
end;

procedure TVpZeosDatastore.CreateTables;
var
  wasConnected: Boolean;
begin
  if FConnection = nil then
    raise EVpException.Create('Database must be connected in order to create tables.');

  wasConnected := FConnection.Connected;
  try
    // Make sure that Connection property has been set
    if not wasConnected then
      SetTableconnections(FConnection);
    CreateAllTables;
  finally
    Connected := wasConnected;
  end;
end;

procedure TVpZeosDatastore.FixContactsTable;
var
  list: TStrings;
  autocommit: Boolean;
  fieldnames: TStrings;
begin
  autocommit := FConnection.AutoCommit;
  ContactsTable.Close;
  list := TStringList.Create;
  try
    FConnection.GetColumnNames(ContactsTableName, '', list);
    FConnection.AutoCommit := false;
    try
      // Fields renamed in 1.05
      fieldnames := TStringList.Create;
      try
        if list.IndexOf('Address') > -1 then fieldnames.Add('Address|Address1');
        if list.IndexOf('City') > -1 then fieldnames.Add('City|City1');
        if list.IndexOf('State') > -1 then fieldnames.Add('State|State1');
        if list.IndexOf('Zip') > -1 then fieldnames.Add('Zip|Zip1');
        if list.IndexOf('Country') > -1 then fieldnames.Add('Country|Country1');
        if list.IndexOf('EMail') > -1 then fieldnames.Add('EMail|EMail1');
        if fieldnames.Count > 0 then begin
          RenameFields(ContactsTableName, fieldnames);
          exit;   // This automatically creates the new fields
        end;
      finally
        fieldnames.Free;
      end;

      // Fields added in 1.05
      if list.IndexOf('Department') = -1 then
        AddField(ContactsTableName, 'Department', ftString, 50);
      if list.IndexOf('AddressType1') = -1 then
        AddField(ContactsTableName, 'AddressType1', ftInteger);
      if list.IndexOf('AddressType2') = -1 then
        AddField(ContactsTableName, 'AddressType2', ftInteger);
      if list.IndexOf('Address2') = -1 then
        AddField(ContactsTableName, 'Address2', ftString, 100);
      if list.IndexOf('City2') = -1 then
        AddField(ContactsTableName, 'City2', ftString, 50);
      if list.IndexOf('State2') = -1 then
        AddField(ContactsTableName, 'State2', ftString, 25);
      if list.IndexOf('Zip2') = -1 then
        AddField(ContactsTableName, 'Zip2', ftString, 10);
      if list.IndexOf('country2') = -1 then
        AddField(ContactsTableName, 'Country2', ftString, 25);
      if list.IndexOf('EMail2') = -1 then
        AddField(ContactsTableName, 'EMail2', ftString, 100);
      if list.IndexOf('EMail3') = -1 then
        AddField(ContactsTableName, 'EMail3', ftString, 100);
      if list.IndexOf('EMailType1') = -1 then
        AddField(ContactsTableName, 'EMailType1', ftInteger);
      if list.IndexOf('EMailType2') = -1 then
        AddField(ContactsTableName, 'EMailType2', ftInteger);
      if list.IndexOf('EMailType3') = -1 then
        AddField(ContactsTableName, 'EMailType3', ftInteger);
      if list.IndexOf('Website1') = -1 then
        AddField(ContactsTableName, 'Website1', ftString, 100);
      if list.IndexOf('Website2') = -1 then
        AddField(ContactsTableName, 'Website2', ftString, 100);
      if list.IndexOf('WebsiteType1') = -1 then
        AddField(ContactsTableName, 'WebsiteType1', ftInteger);
      if list.IndexOf('WebsiteType2') = -1 then
        AddField(ContactsTableName, 'WebsiteType2', ftInteger);

      FConnection.Commit;
    except
      FConnection.Rollback;
      raise Exception.Create('Failure to update table structure to current VisualPlanIt version');
    end;
  finally
    list.Free;
  end;

  FConnection.Connected := false;
  FConnection.AutoCommit := autocommit;
  FConnection.Connected := true;
end;

function TVpZeosDatastore.GetContactsTable: TDataset;
begin
  Result := FContactsTable;
end;

function TVpZeosDatastore.GetEventsTable: TDataset;
begin
  Result := FEventsTable;
end;

{ This is not needed in the ZEOS datastore as these tables use
  autoincrement fields. }
function TVpZeosDatastore.GetNextID(TableName: string): integer;
begin
  Result := -1;
end;

function TVpZeosDatastore.GetResourceTable : TDataset;
begin
  Result := FResourceTable;
end;

function TVpZeosDatastore.GetTasksTable : TDataset;
begin
  Result := FTasksTable;
end;

{ Removes all contacts of the specified resource from the database. }
procedure TVpZeosDataStore.InternalPurgeContacts(Res: TVpResource);
var
  sql: String;
begin
  sql := Format('DELETE FROM Contacts WHERE ResourceID = %d', [Res.ResourceID]);
  FConnection.ExecuteDirect(sql);
end;

{ Removes all events of the specified resource from the database. }
procedure TVpZeosDatastore.InternalPurgeEvents(Res: TVpResource);
var
  sql: String;
begin
  sql := Format('DELETE FROM Events WHERE ResourceID = %d', [Res.ResourceID]);
  FConnection.ExecuteDirect(sql);
end;

{ Removes all tasks of the specified resource from the database. }
procedure TVpZeosDatastore.InternalPurgeTasks(Res: TVpResource);
var
  sql: String;
begin
  sql := Format('DELETE FROM Tasks WHERE ResourceID = %d', [Res.ResourceID]);
  FConnection.ExecuteDirect(sql);
end;

procedure TVpZeosDatastore.Loaded;
begin
  inherited;
  if not (csDesigning in ComponentState) then
    Connected := AutoConnect and (
      AutoCreate or
      (FContactsTable.Exists and FEventsTable.Exists and FResourceTable.Exists and FTasksTable.Exists)
    );
end;

procedure TVpZeosDatastore.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if (Operation = opRemove) and (AComponent = FConnection) then
    FConnection := nil;
end;

{ Renames the fields specified in the list. Each list item contains old and new
  fieldnames separated by a bar character (|).

  Note that sqlite3 does not provide a command for renaming of fields. Therefore,
  the old table is renamed to a temp table, a new table with the renamed fields
  is created and the content of the temp table is copied to the new table.
  Finally the temp table is deleted.

  See:
  https://stackoverflow.com/questions/805363/how-do-i-rename-a-column-in-a-sqlite-database-table

  TO DO:
  Take care of the case that a renamed field belongs to an index, constraint, etc.
  (this case is ignored currently). }
procedure TVpZeosDatastore.RenameFields(ATableName: String; AFields: TStrings);
const
  NO_INDEX = false;
var
  sql: String;
  oldFields: TStrings;
  oldfn, newfn: String;
  srcfn, destfn: String;
  i, j, p: Integer;
  done: Boolean;
begin
  oldfields := TStringList.Create;
  try
    FConnection.GetColumnNames(ATableName, '', oldfields);

    { 1 - Rename old table (append _TMP to tablename) }
    sql := Format('ALTER TABLE %0:s RENAME TO %0:s_TMP;', [ATableName]);
    FConnection.ExecuteDirect(sql);

    { 2 - Create new table }
    if ATableName = ContactsTableName then
      CreateTable(ContactsTableName, NO_INDEX) else
    if ATablename = EventsTableName then
      CreateTable(EventsTablename, NO_INDEX) else
    if ATableName = ResourceTableName then
      CreateTable(ResourceTableName, NO_INDEX) else
    if ATableName = TasksTableName then
      CreateTable(TasksTableName, NO_INDEX)
    else
      raise Exception.Create('Unknown table in RenameFields.');

    { 3 - Copy contents from temp table to new table }
    srcfn := '';
    destfn := '';
    for i:=0 to oldfields.Count-1 do begin
      done := false;
      // Is field "oldfields[i]" contained in the list of fields to be renamed?
      for j:=0 to AFields.Count-1 do begin
        p := pos('|', AFields[j]);
        oldfn := copy(AFields[j], 1, p-1);
        newfn := copy(AFields[j], p+1, MaxInt);
        if oldfn = oldfields[i] then begin
          // yes: add old field name to srcfn, new field name to destfn
          srcfn := srcfn + ',' + oldfn;
          destfn := destfn + ',' + newfn;
          done := true;
          break;
        end;
      end;
      if not done then begin
        // no: add current field name to srcfn and destfn
        srcfn := srcfn + ',' + oldfields[i];
        destfn := destfn + ',' + oldfields[i];
      end;
    end;
    // Remove the beginning comma added above.
    if srcfn <> '' then System.Delete(srcfn, 1, 1);
    if destfn <> '' then System.Delete(destfn, 1, 1);
    // Execute INSERT command
    sql := Format(
      'INSERT INTO %0:s (%1:s) SELECT %2:s FROM %0:s_TMP;', [
      ATableName, destfn, srcfn
    ]);
    FConnection.ExecuteDirect(sql);

    { 4 - Finally delete the temp table }
    sql := Format('DROP TABLE %s_TMP;', [ATableName]);
    FConnection.ExecuteDirect(sql);

    FConnection.Disconnect;
    FConnection.Connect;
  finally
    oldfields.Free;
  end;
end;

procedure TVpZeosDatastore.SetConnected(const AValue: Boolean);
var
  canLoad: Boolean = false;
begin
  if (AValue = Connected) or (FConnection = nil) then
    exit;

  if AValue and AutoCreate and not TablesExist then
    CreateTables;

  FConnection.Connected := AValue;

  if FConnection.Connected and TablesExist then begin
    FContactsTable.Open;
    // If field "Department" does not exist then it is an old table and must be reworked.
    if ContactsTable.Fields.FindField('Department') = nil then
    begin
      FixContactsTable;
      FContactsTable.Open;
    end;
    FEventsTable.Open;
    FResourceTable.Open;
    FTasksTable.Open;
    canLoad := true;
  end;

  inherited SetConnected(AValue);

  if canLoad then
    Load;
end;

procedure TVpZeosDatastore.SetConnection(const AValue: TZConnection);
var
  wasConnected: Boolean;
begin
  if AValue = FConnection then
    exit;

  wasConnected := (AValue <> nil) and AValue.Connected and
    (FConnection <> nil) and FConnection.Connected;

  FConnection := AValue;
  
  AdjustSQLFieldTypeNames;

  if not Connected then
    SetTableConnections(FConnection);

  if AutoCreate and (FConnection <> nil) then
    CreateTables;

  if Autoconnect or wasConnected then
    Connected := true;
end;

// Must be disconnected!
procedure TVpZeosDatastore.SetTableConnections(AConnection: TZConnection);
begin
  if FContactsTable.Connection = nil then begin
    FContactsTable.Connection := AConnection;
    FEventsTable.Connection := AConnection;
    FResourcetable.Connection := AConnection;
    FTaskstable.Connection := AConnection;
  end;
end;

function TVpZeosDatastore.TableExists(ATableName: String): Boolean;
var
  L: TStringList;
begin
  Result := false;
  if not FConnection.Connected then
    exit;

  L := TStringList.Create;
  try
    L.CaseSensitive := false;
    FConnection.GetTableNames('', L);
    Result := L.IndexOf(ATablename) <> -1;;
  finally
    L.Free;
  end;
end;

function TVpZeosDatastore.TablesExist: Boolean;
var
  L: TStringList;
begin
  Result := false;
  if not FConnection.Connected then
    exit;

  L := TStringList.Create;
  try
    L.CaseSensitive := false;
    FConnection.GetTableNames('', L);
    Result := (L.IndexOf(FContactsTable.TableName) <> -1) and
              (L.IndexOf(FEventsTable.TableName) <> -1) and
              (L.IndexOf(FResourceTable.TableName) <> -1) and
              (L.IndexOf(FTasksTable.TableName) <> -1);
  finally
    L.Free;
  end;
end;

end.