SQLite-backed tables

OpenADS can open and drive a SQLite database through the same ACE / rddads surface used for DBF / ADT tables. From the point of view of a Harbour / Clipper / X# application the SQLite table behaves like an ordinary work area — navigation (Skip, GoTop, GoBottom), field read/write, and the standard Ads* calls all work.

Requirements

• OpenADS built with OPENADS_WITH_SQLITE — this is ON by default in CMakeLists.txt (the SQLite amalgamation is vendored via FetchContent).
• The connection URI must start with sqlite:// followed by the path to the .db file.

How it works

The SQLite path is selected entirely by the connection URI. AdsConnect60 calls parse_sqlite_uri(); when the URI matches sqlite://… it opens a SqliteConnection instead of the native DBF/CDX engine. Every later ACE call (AdsOpenTable90, AdsGetField, AdsSetField, AdsSkip, AdsSeek, AdsCreateIndex61, …) is routed to the SQLite backend.

1. Connect with a sqlite:// URI

LOCAL hConn
AdsConnect60( "sqlite:///path/to/database.db", ;
              ADS_LOCAL_SERVER, NIL, NIL, 0, @hConn )

The third slash is the leading / of the absolute file path, so sqlite:///tmp/app.db opens /tmp/app.db.

2. Open an existing table

Through rddads the table opens like any other work area:

USE customers VIA "ADSCDX" NEW SHARED

(X# applications use the AXDBFCDX RDD; the ACE-level routing is identical.)

Field-type mapping

The field type is inferred from the SQLite column’s declared type (case-insensitive substring match):

SQLite declared type contains	OpenADS field type	Length
INT	Integer	4
REAL / FLOA / DOUB	Double	8 (6 dec)
BLOB	Binary	10
anything else (e.g. TEXT)	Character	64

Encryption

A cipher key can be supplied as a query parameter; it is URL-decoded before use:

AdsConnect60( "sqlite:///path/db.sqlite?key=mypassword", ;
              ADS_LOCAL_SERVER, NIL, NIL, 0, @hConn )

Current limitations

• Open only — AdsCreateTable does not create SQLite tables. Passing a SQLite connection handle falls back to the native DBF path; create the schema in SQLite directly instead.
• Indexes are exposed as SqliteIndex with basic seek / next / prev that map to ORDER BY queries.
• Transactions map to ordinary SQLite transactions.

Other SQL backends (OpenADS Plus)

SQLite is one of four SQL backends selected the same way — by the connection URI. PostgreSQL, MariaDB / MySQL and any ODBC-reachable engine are also supported behind the ACE ABI:

Backend	Connection URI
SQLite	sqlite:///path/to/db.sqlite[?key=…]
PostgreSQL	postgresql://user:pass@host:5432/dbname
MariaDB / MySQL	mariadb://user:pass@host:3306/dbname
ODBC (any)	odbc://Driver={…};Server=…;Database=…;UID=…;PWD=…

All four sit behind a single pluggable backend-ops registry (one BackendTableOps struct + one registration line per backend), so the ABI navigation / field functions stay backend-agnostic. Read + navigation + column SEEK work today; write is per-backend. Identifiers are restricted to safe ASCII and SEEK values use prepared-statement parameters. See docs/OPENADS_PLUS.md.