At 9:03 AM -0400 11/1/07, D. Richard Hipp wrote:
The current virtual-table implementation does not work when you have
shared cache mode enabled. We would like to fix this so that that you can
(for example) use FTS and shared cache at the same time. But to do so
seems likely to require an incompatible change to the virtual-table interface.
The virtual-table interface is currently listed as "experimental" and does
not appear in the "official" documentation in capi3ref.html. So we are free
to change it if we need to. But I wonder how many people this would
inconvenience.
If you have or know of a virtual table implementation (other than the ones
that are included with SQLite - such as FTS1-3) that will be broken by an
API change, please let me know. And please also advice me how much of
a hardship a change would be for you.
While you're at it, I strongly recommend changing the feature name
from "virtual table" to "federated table", or at least not something
called "virtual", because the older/current name is a source of
confusion.
In general relational database contexts, the term "virtual table"
usually means the same thing as "view" means, which is something that
looks like a "real/base table" but is actually a mapping to one or
more real/base tables as typically defined by a relational query, and
this is done internally by the main DBMS that does the real/base
tables.
(In fact, a proper viewed/virtual table implementation would be such
that users of the database don't have to know which tables are base
or viewed, and if a DBA wanted to change the schema later to make
viewed tables real and real tables viewed, it would not affect the
users. Views that don't reflect enough mapping data notwithstanding.)
Your term "virtual table" would be better called "federated table"
(or "foreign table" or "remote table"), which is the more standard
term with relational databases for tables that are interfaces to
other DBMS systems with remote storage.
If you're making an incompatible change anyway, then this rename
would be good for hand-in-hand with it, to help people migrating apps
from the old to the new; best to do all the incompatible changes at
once.
-- Darren Duncan
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