Custom fields serialization extending TSQLRecordHistory

EMartin · 2017-12-01 21:53:25

Hi @ab,

I need more fields in inherited TSQLRecordHistory:

  TSQLARISHistory = class(TSQLRecordHistory)
  protected
    fLogonName: RawUTF8;
    fTableName: RawUTF8;
    fRecID: TID;
  published
    property LogonName: RawUTF8 index 50 read fLogonName write fLogonName;
    property RecID: TID read fRecID write fRecID;
    property TableName: RawUTF8 index 50 read fTableName write fTableName;
  end;

and I have modified mORMot.pas in this way:

interface
...

type
  ...
  TSQLRestServer = class(TSQLRest)
  protected
    ...
    function MainEngineUpdateFieldIncrement(TableModelIndex: integer; ID: TID;
      const FieldName: RawUTF8; Increment: Int64): boolean; virtual; abstract;
    /// Fields serialization for history tracking changes
    // - Fields: name value pairs for JSON serialization.
    // - JSON: JSON serialized fields
    procedure DoHistoryFieldsSerialization(const Fields: array of const; var JSON: RawUTF8); virtual;
    ...
 end;

implementation
...
procedure TSQLRestServer.DoHistoryFieldsSerialization(const Fields: array of const; var JSON: RawUTF8);
begin
  JSON := JSONEncode(Fields);
end;

function TSQLRestServer.InternalUpdateEvent(aEvent: TSQLEvent; aTableIndex: integer;
  aID: TID; const aSentData: RawUTF8; aIsBlobFields: PSQLFieldBits): boolean;
procedure DoTrackChanges;
var TableHistoryIndex: integer;
    JSON: RawUTF8;
    Event: TSQLHistoryEvent;
begin
  case aEvent of
  seAdd:    Event := heAdd;
  seUpdate: Event := heUpdate;
  seDelete: Event := heDelete;
  else exit;
  end;
  TableHistoryIndex := fTrackChangesHistoryTableIndex[aTableIndex];
  fAcquireExecution[execORMWrite].Safe.Lock; // avoid race condition
  try // low-level Add(TSQLRecordHistory) without cache
    DoHistoryFieldsSerialization(['ModifiedRecord',aTableIndex+aID shl 6,'Event',ord(Event),
                        'SentDataJSON',aSentData,'TimeStamp',ServerTimeStamp], JSON); // <<--- call new procedure
    fAcquireExecution[execORMWrite].fSafe.Lock;
    try // may be within a batch in another thread
      EngineAdd(TableHistoryIndex,JSON);
    finally
      fAcquireExecution[execORMWrite].fSafe.Unlock;
    end;
    { TODO: use a BATCH (in background thread) to speed up TSQLHistory storage }
    if fTrackChangesHistory[TableHistoryIndex].CurrentRow>
        fTrackChangesHistory[TableHistoryIndex].MaxSentDataJsonRow then begin
      // gather & compress TSQLRecordHistory.SentDataJson into History BLOB
      TrackChangesFlush(TSQLRecordHistoryClass(Model.Tables[TableHistoryIndex]));
      fTrackChangesHistory[TableHistoryIndex].CurrentRow := 0;
    end else
      // fast append as JSON until reached MaxSentDataJsonRow
      inc(fTrackChangesHistory[TableHistoryIndex].CurrentRow);
  finally
    fAcquireExecution[execORMWrite].Safe.UnLock;
  end;
end;
begin
  ...
end;

and I implemented DoHistorySerialization in my code:

  ...
  procedure TARISRestServer.DoHistoryFieldsSerialization(const Fields: array of const; var JSON: RawUTF8);
  var
    lFields: TDocVariantData;
  begin
    lFields.InitObject(Fields);
    lFields.AddValue('LogonName',ServiceContext.Request.SessionUserName);
    lFields.AddValue('RecID',lFields.Value['ModifiedRecord'] shr 6);
    lFields.AddValue('TableName',fModel.Tables[lFields.I['ModifiedRecord'] and 63].SQLTableName);
    JSON := lFields.ToJSON;
  end;
  ...

and all works OK !!!

Are you agree with this modification and can you apply them ?

Thanks in advance.

EMartin · 2017-12-03 16:22:20

Do you not agree ?

ab · 2017-12-03 20:24:27

Made more sense to me to add a virtual method at TSQLRecordHistory level.

Please check https://synopse.info/fossil/info/7d7b243077

Thanks for the proposal!

EMartin · 2017-12-04 13:39:47

Thank you @ab, works fine !!!

lagodny · 2020-01-02 12:03:09

Well I overridden InitializeFields and got extra fields in the table. Works great.
But what about compression? How to save these fields during compression? Maybe it makes sense to make HistoryAdd virtual in order to be able to add additional fields? Would that be enough?

mORMot Open Source

#1 2017-12-01 21:53:25

Custom fields serialization extending TSQLRecordHistory

#2 2017-12-03 16:22:20

Re: Custom fields serialization extending TSQLRecordHistory

#3 2017-12-03 20:24:27

Re: Custom fields serialization extending TSQLRecordHistory

#4 2017-12-04 13:39:47

Re: Custom fields serialization extending TSQLRecordHistory

#5 2020-01-02 12:03:09

Re: Custom fields serialization extending TSQLRecordHistory

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