Again found when fuzzing nested where clause subqueries:
Aggregate registers need to be NULLed at the start because the same
registers might be reused on another invocation of a subquery, and if
they are not NULLed, the 2nd invocation of the same subquery will have
values left over from the first invocation.
Reviewed-by: Preston Thorpe (@PThorpe92)
Closes#1614
Currently we have this:
program.alloc_cursor_id(Option<String>, CursorType)`
where the String is the table's name or alias ('users' or 'u' in
the query).
This is problematic because this can happen:
`SELECT * FROM t WHERE EXISTS (SELECT * FROM t)`
There are two cursors, both with identifier 't'. This causes a bug
where the program will use the same cursor for both the main query
and the subquery, since they are keyed by 't'.
Instead introduce `CursorKey`, which is a combination of:
1. `TableInternalId`, and
2. index name (Option<String> -- in case of index cursors.
This should provide key uniqueness for cursors:
`SELECT * FROM t WHERE EXISTS (SELECT * FROM t)`
here the first 't' will have a different `TableInternalId` than the
second `t`, so there is no clash.
Currently we have some usages of LIMIT where the actual limit counter
is initialized next to the DecrJumpZero instruction, and then
`program.mark_last_insn_constant()` is used to hoist the counter
initialization to the beginning of the program.
This is very fragile, and already FROM clause subquery handling works
around this with a hack (removed in this PR), and (upcoming) WHERE clause
subqueries would also run into problems because of this, because the LIMIT
might need to be initialized once for every iteration of the subquery.
This PR removes those usages for LIMIT, and LIMIT processing is now more
intuitive:
- limit counter is now initialized at the start of the query processing
- a function init_limit() is extracted to do this for select/update/delete
This PR introduces some modifications to the Program Builder to allow us
to use nested parsing. By focusing the emission of Init and the last
Goto (prologue and epilogue), inside the ProgramBuilder, we can just not
emit them if we are parsing/translating in a nested context. For this
PR, I only migrated insert to use these functions as I need them to
support Insert statements that use `SELECT FROM` syntax. Nested parsing
overall enables code reuse for us and arguably is one of the only ways
to parse deeply nested queries without a lot of code duplication.
#1528Closes#1543
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
Reviewable commit by commit. CI failures are not related.
Adds support for e.g. `select first_name, sum(distinct age),
count(distinct age), avg(distinct age) from users group by 1`
Implementation details:
- Creates an ephemeral index per distinct aggregate, and jumps over the
accumulation step if a duplicate is found
Closes#1507
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!)
We've run into trouble in multiple places due to the fact that
we delete terms from the where clause (e.g. when a constant condition
is removed, or the term becomes part of an index seek key).
A simpler solution is to add a flag indicating that the term is
consumed (used), so that it is not translated in the main loop
anymore when WHERE clause terms are evaluated.
