On Mon, Mar 7, 2011 at 11:53 PM, RAKESH HEMRAJANI
<rakesh_hemraj...@hotmail.com> wrote:
> I am newbie to sqlite, have started understanding the code, at the moment m
> stuck and not able to understand how to generate byte code
Depending on how strongly wedded you are to syntax, you might be able
to avoid VDBE code generation. If syntax is not that important then
your best bet is probably to use virtual tables and user-defined
functions, re-entering SQLite3 to use an actual table under the covers
-- the virtual tables would provide the sequence abstraction, and the
functions would provide the nextval/currval interface. Instead of
CREATE SEQUENCE you'd have CREATE VIRTUAL TABLE, and instead of
sequence_name.NEXTVAL you'd have nextval('sequence_name'). The
virtual table would just create a table with a single column as an
alias for the rowid column, and the function would just do an insert
into that table and would then return the rowid of the last inserted
row. If you don't need the full set of sequence options you could even
dispense with the virtual table.
Another option, if you care about syntax but still don't want to muck
with VDBE code generation would be to parse the syntax you care about
and convert it to the CREATE VIRTUAL TABLE / nextval() alternative I
gave you above. You could even implement this as a SQL->SQL
re-writer, completely outside of SQLite3. With this approach and a
little care you could even avoid the need for a virtual table and
function.
Nico
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