Efficient database access to various DBMS from Delphi XE2

Question 1

If you are using XE2, I would recommend dbExpress.

It supports ODBC (but not for SAP HANA)
Unidirectional datasets can be used with ClientDataSet for caching. In fact, ClientDataSets can be used to cache any dataset component.

If you are using XE3 or later, I would recommend FireDAC.

Embarcadero purchased AnyDAC and have renamed it FireDAC.
It is included with the Enterprise SKU and above. A free download is available for licensed XE3 users.
I believe this will be their data access strategy going forward. See this recent blog post.

I understand FireDAC can be used with XE2, but I'm not sure if there are any issues.

Question 2

I decided to conduct a little performance research: UniDAC (5.0.1) vs FireDAC (8.0.1), on Delphi XE3. Databases: Firebird, MySQL & SQL Server.

Here are the 150k records fetch results (memory usage was considered as the difference between before and after fetching).

Firebird:

CREATE TABLE TEST_PERF (
    ID  INTEGER PRIMARY KEY,
    VC  VARCHAR(200),
    NM  NUMERIC(18,2),
    DT  TIMESTAMP
)

UniDAC - 0,909 seconds, ate 12 324 044 of memory

FireDAC - 0,967 seconds, ate 282 179 668 of memory (I'm shocked)

MySQL:

CREATE TABLE TEST_PERF (
    ID  INTEGER PRIMARY KEY,
    VC  VARCHAR(200),
    NM  NUMERIC(18,2),
    DT  DATETIME
)

UniDAC - 0,363 seconds and 11 552 604 of memory

FireDAC - 0,713 seconds and 49 375 108 of memory

SQL Server:

CREATE TABLE TEST_PERF (
    ID  INTEGER PRIMARY KEY,
    VC  VARCHAR(200),
    NM  NUMERIC(18,2),
    DT  DATETIME
)

UniDAC - 0,391 seconds and 14 155 576 of memory

FireDAC - 0,324 seconds and 51 775 844 of memory

Everything was measured simply:

function MemoryUsed: Cardinal;
var
  st: TMemoryManagerState;
  sb: TSmallBlockTypeState;
begin
  GetMemoryManagerState(st);
  Result := st.TotalAllocatedMediumBlockSize + st.TotalAllocatedLargeBlockSize;
  for sb in st.SmallBlockTypeStates do
    Result := Result + sb.UseableBlockSize * sb.AllocatedBlockCount;
end;

  UniQuery1.SQL.Text := 'select * from test_perf';
  UniQuery1.SpecificOptions.Values['FetchAll'] := 'True';
  mem := MemoryUsed;
  tc := Now;
  UniQuery1.Open;
  UniQuery1.Last;
  tc := Now - tc;
  mem := MemoryUsed - mem;
  Memo1.Lines.Add('UniDAC Firebird: Time: ' + FloatToStr(tc * 24 * 60 * 60) + ' sec; Memory used: ' + IntToStr(mem));

  ADQuery1.SQL.Text := 'select * from test_perf';
  ADQuery1.FetchOptions.Mode := fmAll;
  mem := MemoryUsed;
  tc := Now;
  ADQuery1.Open;
  ADQuery1.Last;
  tc := Now - tc;
  mem := MemoryUsed - mem;
  Memo1.Lines.Add('FireDAC Firebird: Time: ' + FloatToStr(tc * 24 * 60 * 60) + ' sec; Memory used: ' + IntToStr(mem));

If anyone is interested, here is the test application, you can add there performance comparison for ADO, dbExpress, ZeosLib, and others you are interested in.

Question 3

I always use ADO - used it with SQLServer, Oracle, Sybase, PostGreSQL and others. You can find an ADO provider for just about any database. Never had a problem I was not able to work out with a bit of research. Since ADO is so widely used, most of the problems are well known. And UDL files can make your life a lot easier.

But I never use the Delphi ADO components on the component palette - either I use them in memory, or more often, dump the results of the ADO calls directly into a TKBMMemtable and avoid the Delphi 'out of the box' stuff entirely. You can write a utility function that will do it automatically for you.

Question 4

Firedac-Comes with Delphi,So probably you´ll have to pay for it anyway. UNidac-Faster and let you not have to upgrade Delphi so frequentely,in order to have the data Acess being update,also if you one day decide to go to Lazzarus you save a lot of work too.

Question 5

There are many misconceptions in many of the threads so I´ll try to give my 2 cents. The problem is that we Delphians used to think in executables,so we look for ways of moving data(specially when our database and application server are hosted outside); These scenarios will never beat a RIA application, because you don´t move data anymore,but just a representation of the screen. Another misconception is saying that TDATASET does not work well with AJAX. Just see some UNIGUI examples on youtube. BTW I'm using ordinary DataSnap with a clientdataset, not ORM.

Efficient database access to various DBMS from Delphi XE2

My needs

My guesses

What I found so far