README

FireDAC-BDE

FireDAC driver for the BDE

A FireDAC physical driver (DriverID=BDE) that lets modern FireDAC code read and write legacy dBase III/IV (.DBF) and Paradox 7+ (.DB) tables through the Borland Database Engine (BDE).

You keep using TFDConnection, TFDQuery, TFDTable, transactions and parameters as with any other FireDAC database; the driver takes care of talking to the BDE underneath.

Unofficial, community project. Not affiliated with or endorsed by Embarcadero. Developed and tested with Delphi 13.2, Windows 32-bit only (the BDE is 32-bit). 🇮🇹 Leggi in italiano

Why

Migrating an application from BDE to FireDAC is easy; migrating the data usually isn't (shared DBF/Paradox files used by other legacy programs). This driver lets new FireDAC code work directly on the legacy files while the old programs keep running, with no hybrid infrastructure and no code that is specific to a database.

Features

• Connection through a BDE alias or a plain folder path (no alias needed).
• Metadata: table list, fields, indexes, primary key (TFDMetaInfoQuery, GetTableNames, GetFieldNames, ...).
• TFDQuery / TFDTable / TFDCommand with named parameters, fetch of all field types including memo and BLOB.
• Updates through Edit/Post, Append, Delete, and direct UPDATE/INSERT/DELETE.
• Transactions (StartTransaction/Commit/Rollback) – tested with rollback on both DBF and Paradox.
• Shared access with other applications, record-lock errors mapped to ekRecordLocked, configurable lock wait (LockRetry).
• DBF and Paradox files with the same base name coexisting in one folder.
• Design-time package (component TFDPhysBDEDriverLink).

Requirements

• Delphi with FireDAC (developed on 13.2; other versions untested – reports welcome).
• A working BDE installation (bdertl package, Borland Database Engine on the machine). The BDE is a legacy Embarcadero product; obtain it according to your own license. Nothing from the BDE or FireDAC sources is included here.
• Build target: Windows 32-bit.

Installation

1. Clone the repository (git clone https://github.com/<your-user>/Firedac-BDE.git) and open FDBDE_D132.groupproj (target platform Win32).
2. Build FDBDERun (runtime package, requires bdertl).
3. Build and Install FDBDEDesign (design-time package).
4. In your projects either add FDBDERun to the runtime packages, or just add FireDAC.Phys.BDEDef and FireDAC.Phys.BDE to a uses clause: the driver registers itself in the initialization section.

Command line (Windows, Delphi 13): build.bat [Debug|Release] builds the packages and BDETest; test.bat runs BDETest on a copy of the synthetic sample data; install-ide.bat registers the design-time package in the IDE (close RAD Studio first); clean.bat removes generated files. Other Delphi versions: set BDSVER=<n> or set RSVARS=<path to rsvars.bat>.

If the compiler cannot find FireDAC.inc, add $(BDS)\source\data\firedac to the library/search path (do not copy that file into the repository, it belongs to Embarcadero).

Usage

FDConnection1.DriverName := 'BDE';
FDConnection1.Params.Database := 'C:\Data\Legacy';   // folder with .DBF/.DB, or a BDE alias
FDConnection1.Params.Values['LockRetry'] := '1';     // optional
FDConnection1.Open;

// Table names must carry the extension and be double-quoted in SQL
FDQuery1.Open('select * from "CUSTOMERS.DBF" where ID = :id', [42]);

// Updating a DBF needs a UNIQUE key field (DBF has no primary key)
FDQuery1.UpdateOptions.UpdateTableName := 'CUSTOMERS.DBF';
FDQuery1.UpdateOptions.KeyFields := 'ID';
FDQuery1.Edit;
FDQuery1.FieldByName('NAME').AsString := 'New name';
FDQuery1.Post;

Connection parameters

Things to know (limitations)

• Windows 32-bit only. The BDE does not exist for 64-bit.
• SQL dialect = BDE Local SQL: no LIMIT/TOP, CASE, COALESCE, CURRENT_DATE, LENGTH, few functions, limited joins/subqueries; LIKE is case-sensitive; use parameters for dates. FireDAC does skip/limit on the client side. See docs/LOCAL_SQL.md. For CASE, COALESCE, LIMIT, CTEs or joins across sources you can run FireDAC's own Local SQL (SQLite virtual tables) on top of the driver: docs/LOCAL_SQL_ON_BDE.md (experimental).
• File extensions. A folder can hold CLIENTS.DB and CLIENTS.DBF. Always use the extension and double quotes in SQL ("CLIENTS.DBF"); without it the BDE picks Paradox.
• DBF has no primary key. Set UpdateOptions.KeyFields to a field that is really unique, otherwise FireDAC reports "Exact update affected [N] rows".
• Memo parameters. To write a memo with hand-written SQL, give the parameter a memo type (DataType := ftWideMemo; AsWideMemo := ...). A plain string parameter on a memo column raises no error on Paradox/dBase but writes nothing. Edit/Post is not affected.
• Rollback of an empty memo (dBase III). Rolling back a transaction that gave a value to a memo that was previously empty can leave the BDE in an inconsistent state: the next query on that row fails with "BLOB already opened". Rows with an existing memo are not affected. Close and reopen the connection after such a rollback. (BDE behaviour, seen on dBase III; not seen on dBase IV.)
• Locks. Waiting time on a locked record is governed by the BDE; use LockRetry. In the tests a row modified inside an open transaction stayed locked for other connections until commit/rollback, on both DBF and Paradox.
• "Insufficient disk space" at random. A BDE bug (free space near a multiple of 4 GB), not a driver one. Fix: put Demos\FixBDE4GbBug.pas first in the uses of your program. See docs/BDE_4GB_BUG.md.
• One BDE session per connection; the BDE is not designed for heavy multi-threading.
• Strings are exposed as Unicode; the conversion uses the table's language driver, so characters outside the table's code page may not survive a round trip.
• Memo text is decoded with the system ANSI code page. If an application stored UTF-8 inside a memo (for example XML with a BOM), you get the UTF-8 bytes as ANSI characters (<?xml ...). The conversion is lossless: re-decode in your code with TEncoding.UTF8.GetString(TEncoding.ANSI.GetBytes(S)).
• Not implemented: DDL helpers (create/alter table through FireDAC), stored procedures, event alerts, array DML optimisation (arrays are executed row by row).

What has been tested

Real-world dBase IV (≈3,600 rows, 119 fields, memo) and Paradox tables, Delphi 13.2, with Demos\BDETest:

Trying it

python Tools/make_sample_dbf.py            # creates Demos/Data/SAMPLE.DBF + .DBT (synthetic data)
Demos\BDETest.exe Demos\Data SAMPLE.DBF ID NAME NOTES

BDETest <folder|alias> <TABLE.DB|DBF> [key field] [text field] [memo field] [row 1-5] [date field]

With a key, text and memo field the test also performs update, insert, delete and memo writes inside a transaction that is rolled back, and a lock test with a second connection. Run the write tests on a copy of your data. BDETest takes an optional 6th parameter (row 1-5 of the sample used as key); row 3 of SAMPLE.DBF has a memo, row 1 has none. A Paradox sample can be created with Tools\MakeSampleParadox.dpr (untested).

Repository layout

Source/      driver units (BDEDef, BDEMeta, BDE) + design-time registration (BDEReg)
Packages/    Delphi packages (d132 = Delphi 13.2)
Demos/       BDETest console program + synthetic sample data, FixBDE4GbBug unit
Tools/       sample data generators
docs/        architecture notes

Source comments and the test program messages are in Italian.

Contributing

Bug reports and test results on other Delphi versions or table types are very welcome – see CONTRIBUTING.md.

License

MIT. FireDAC, the BDE and Delphi are products of Embarcadero Technologies.