Database::get_table currently either returns a RefPtr to an existing
table, a nullptr if the table doesn't exist, or an Error if some
internal error occured. Change this to return a NonnullRefPtr to an
exisiting table, or a SQL::Result with any error, including if the
table was not found. Callers can then handle that specific error code
if they want.
Returning a NonnullRefPtr will enable some further cleanup. This had
some fallout of needing to change some other methods' return types from
AK::ErrorOr to SQL::Result so that TRY may continue to be used.
Database::get_schema currently either returns a RefPtr to an existing
schema, a nullptr if the schema doesn't exist, or an Error if some
internal error occured. Change this to return a NonnullRefPtr to an
exisiting schema, or a SQL::Result with any error, including if the
schema was not found. Callers can then handle that specific error code
if they want.
Returning a NonnullRefPtr will enable some further cleanup. This had
some fallout of needing to change some other methods' return types from
AK::ErrorOr to SQL::Result so that TRY may continue to be used.
The result of a SQL statement execution is either:
1. An error.
2. The list of rows inserted, deleted, selected, etc.
(2) is currently represented by a combination of the Result class and
the ResultSet list it holds. This worked okay, but issues start to
arise when trying to use Result in non-statement contexts (for example,
when introducing Result to SQL expression execution).
What we really need is for Result to be a thin wrapper that represents
both (1) and (2), and to not have any explicit members like a ResultSet.
So this commit removes ResultSet from Result, and introduces ResultOr,
which is just an alias for AK::ErrorOrr. Statement execution now returns
ResultOr<ResultSet> instead of Result. This further opens the door for
expression execution to return ResultOr<Value> in the future.
Lastly, this moves some other context held by Result over to ResultSet.
This includes the row count (which is really just the size of ResultSet)
and the command for which the result is for.
The handling of filesystem level errors was basically non-existing or
consisting of `VERIFY_NOT_REACHED` assertions. Addressed this by
* Adding `open` methods to `Heap` and `Database` which return errors.
* Changing the interface of methods of these classes and clients
downstream to propagate these errors.
The constructors of `Heap` and `Database` don't open the underlying
filesystem file anymore.
The SQL statement handlers return an `SQLErrorCode::InternalError`
error code if an error comes back from the lower levels. Note that some
of these errors are things like duplicate index entry errors that should
be caught before the SQL layer attempts to actually update the database.
Added tests to catch attempts to open weird or non-existent files as
databases.
Finally, in between me writing this patch and submitting the PR the
AK::Result<Foo, Bar> template got deprecated in favour of ErrorOr<Foo>.
This resulted in more busywork.
This patch provides very basic, bare bones implementations of the
INSERT and SELECT statements. They are *very* limited:
- The only variant of the INSERT statement that currently works is
SELECT INTO schema.table (column1, column2, ....) VALUES
(value11, value21, ...), (value12, value22, ...), ...
where the values are literals.
- The SELECT statement is even more limited, and is only provided to
allow verification of the INSERT statement. The only form implemented
is: SELECT * FROM schema.table
These statements required a bit of change in the Statement::execute
API. Originally execute only received a Database object as parameter.
This is not enough; we now pass an ExecutionContext object which
contains the Database, the current result set, and the last Tuple read
from the database. This object will undoubtedly evolve over time.
This API change dragged SQLServer::SQLStatement into the patch.
Another API addition is Expression::evaluate. This method is,
unsurprisingly, used to evaluate expressions, like the values in the
INSERT statement.
Finally, a new test file is added: TestSqlStatementExecution, which
tests the currently implemented statements. As the number and flavour of
implemented statements grows, this test file will probably have to be
restructured.
This patch introduces the ability execute parsed SQL statements. The
abstract AST Statement node now has a virtual 'execute' method. This
method takes a Database object as parameter and returns a SQLResult
object.
Also introduced here is the CREATE SCHEMA statement. Tables live in a
schema, and if no schema is present in a table reference the 'default'
schema is implied. This schema is created if it doesn't yet exist when
a Database object is created.
Finally, as a proof of concept, the CREATE SCHEMA and CREATE TABLE
statements received an 'execute' implementation. The CREATE TABLE
method is not able to create tables created from SQL queries yet.
