See https://www.sqlite.org/vtab.html for more details.
This work was started from
https://github.com/gwenn/gosqlite/blob/master/vtab.{c,go} and adds:
- Porting the API to go-sqlite3 APIs.
- Support for >= Go 1.6 without requiring the `cgocheck` flag to be changed.
- Filling out the unfinished callback functions for the `Vtable` struct.
- A simple `Context` API layer for ease of use when adding modules.
Tests are included.
The semantics of sql.Tx.Commit impose that the transaction is
finished and cleaned up by the time the driver's Commit function
returns. However sqlite3 leaves the transaction open if COMMIT
fails due to an SQLITE_BUSY error, so *we* must clean it up.
Closes#184.
The cgo pointer passing rules forbid passing a Go pointer to C if that
pointer points to memory containing other Go pointers. This is true
even if the Go pointer is converted to uintptr.
This change fixes the code to use a handle instead, and to look up the
handle in the callback function.
In Go 1.6, the cgo checking rules are more precise when they see an
address operation as an argument to the C function. When you pass &v[0]
to a C function, the cgo check just verifies that v itself does not
contain any pointers. When you write `p := &v[0]` and then pass p to
the C function, the cgo check is conservative: it verifies that the
entire memory block to which p points does not contain any pointers.
When the bind function is called by code that passes a slice that is
part of a larger struct, this means that the cgo check will look at the
entire larger struct, not just the slice. This can cause a surprising
run time failure.
Avoid this problem by rewriting the code slightly to pass &v[0] in the
call to the C function itself.
In particular this fixes the tests of github.com/jmoiron/sqlx when using
Go 1.6.
Xu Xinran