[odb-users] Index Pragmas DO NOT support index on expressions

[Boris Kolpackov]

Reilly He <reillyhekazusa at gmail.com> writes:

> > So there is still a possibility of, say, renaming the id member but
> > forgetting to update the index definition.
> >
> 
> I got to say I am a little bit confused about this statement, since I take
> a look at the docs of SQLite Alter Table
> <https://www.sqlite.org/lang_altertable.html>, and here I quote:
> 
> > The RENAME COLUMN TO syntax changes the column-name of table table-name
> > into new-column-name. The column name is changed both within the table
> > definition itself *and also within all indexes*, triggers, and views that
> > reference the column. If the column name change would result in a semantic
> > ambiguity in a trigger or view, then the RENAME COLUMN fails with an error
> > and no changes are applied.
> 
> Actually I`ve done my experiment today, and the saying of SQLite was *TRUE*,
> so things like changing the column name actually will not fail any index
> including the changed column.
> 
> but according to your statement, are you saying that if we already add an
> index using ODB`s index pragma, and we somehow *changed the member name*
> (column name), the compiling process of ODB will *fail*?

No, it's in a sense the opposite: if you use raw column names and there
is a mismatch, then the ODB compiler is not going to fail and you will
likely get a runtime error later.

In the example I've given SQLite is smart enough to take care of things
if you are changing the schema. But you could also be creating the
schema (with mismatched column/index) from scratch, say, in a new
database. In this case I am pretty certain you will get a runtime
error since the index will refer to the column that does not exist.