Makes it easier to test the feature:
```
$ cargo run -- --experimental-indexes
Limbo v0.0.22
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database
limbo> CREATE TABLE t(x);
limbo> CREATE INDEX t_idx ON t(x);
limbo> DROP INDEX t_idx;
```
Currently indexes are the bulk of the problem with `UPDATE` and
`DELETE`, while we work on fixing those it makes sense to disable
indexing since they are not stable. We want to try to make everything
else stable before we continue with indexing.
For example, implementing `SELECT DISTINCT` (#1517) and `UNION` (#1545)
require that we are able to create indexes without a rowid column
present. Similarly, `WITHOUT ROWID` tables require this.
I implemented this by replacing the `rowid` and `empty_record`
properties in `BtreeCursor` with
```rust
/// Whether the cursor is currently pointing to a record.
#[derive(Debug, Clone, Copy, PartialEq)]
enum CursorHasRecord {
Yes {
rowid: Option<u64>, // not all indexes and btrees have rowids, so this is optional.
},
No,
}
```
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1518
Previously the Operation enum consisted of:
- Operation::Scan
- Operation::Search
- Operation::Subquery
Which was always a dumb hack because what we really are doing is an
Operation::Scan on a "virtual"/"pseudo" table (overloaded names...)
derived from a subquery appearing in the FROM clause.
Hence, refactor the relevant data structures so that the Table enum now
contains a new variant:
Table::FromClauseSubquery
And the Operation enum only consists of Scan and Search.
```
SELECT * FROM (SELECT ...) sub;
-- the subquery here was previously interpreted as Operation::Subquery on a Table::Pseudo,
-- with a lot of special handling for Operation::Subquery in different code paths
-- now it's an Operation::Scan on a Table::FromClauseSubquery
```
No functional changes (intended, at least!)
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1529
Previously the Operation enum consisted of:
- Operation::Scan
- Operation::Search
- Operation::Subquery
Which was always a dumb hack because what we really are doing is
an Operation::Scan on a "virtual"/"pseudo" table (overloaded names...)
derived from a subquery appearing in the FROM clause.
Hence, refactor the relevant data structures so that the Table enum
now contains a new variant:
Table::FromClauseSubquery
And the Operation enum only consists of Scan and Search.
No functional changes (intended, at least!)
Primary keys that are marked as unique constraint, do not need to have
separate indexes, one is enough. In the case primary key is integer,
therefore rowid alias, we still need an index to satisfy unique
constraint.
