Sibyl
Sibyl is an OCI-based driver for Rust applications to interface with Oracle databases.
Example
use sibyl as oracle; // pun intended :)
Notes on Building
Sibyl needs an installed Oracle client in order to link either to OCI.DLL
on Windows or to libclntsh.so
on Linux. It is expected that on Windows the directory with OCI.DLL
is listed in the PATH
. On Linux, depending on the kind of Oracle client, an additional manual configuration might be needed. Oracle client's lib
directory needs to be present in ld.so.conf
and a link to libclntsh.so
should exist in a directory searched by linkers - /lib64
for example.
Usage
Environment
The OCI environment handle must be created before any other OCI function can be called. While there can be many environments - for example, one can create an environment per connection - usually one is enought. Sibyl initializes it to be the most compatible with Rust requirements - thread-safe using UTF8 character encoding. That single environment handle can be created in main
:
Note however that some function will need a direct refrence to this handle, so instead of passing it around some applications might create it statically:
use Environment;
use lazy_static;
lazy_static!
Then later one would be able to create, for example, a current timestamp as:
use TimestampTZ;
let current_timestamp = from_systimestamp?;
Connections
Use Environment::connect
method to connect to a database:
Where dbname
can be any name that is acceptable by Oracle clients - from local TNS name to Eazy Connect identifier to a connect descriptor.
SQL Statement Execution
All SQL or PL/SQL statements must be prepared before they can be executed:
let stmt = conn.prepare?;
A prepared statement can be executed either with the query
or execute
or execute_into
methods:
query
is used forSELECT
statements. In fact, it will complain if you try toquery
any other statement.execute
is used for all other, non-SELECT, DML and DDL that do not have OUT parameters.execute_into
is used with DML and DDL that have OUT parameters.
query
and execute
take a slice of IN arguments, which can be specified as positional arguments or as name-value tuples. For example, to execute the above SELECT we can call query
using a positional argument as:
let rows = stmt.query?;
or binding :id
by name as:
let rows = stmt.query?;
In most cases which binding style to use is a matter of convenience and/or personal preferences. However, in some cases named arguments would be preferable and less ambiguous. For example, statement changes during development might force the change in argument positions. Also SQL and PL/SQL statements have different interpretation of a parameter position. SQL statements create positions for every parameter but allow a single argument to be used for the primary parameter and all its duplicares. PL/SQL on the other hand creates positions for unique parameter names and this might make positioning arguments correctly a bit awkward when there is more than one "duplicate" name in a statement.
execute_into
allows execution of statements with OUT parameters. For example:
let stmt = conn.prepare?;
let mut department_id: u32 = 0;
let num_inserted = stmt.execute?;
execute
and execute_into
return the number of rows affected by the statement. query
returns what is colloquially called a "streaming iterator" which is typically iterated using while
. For example (continuing the SELECT example from above):
let employees = new;
let rows = stmt.query?;
while let Some = rows.next?
There are a few notable elements in the last example:
- Sibyl uses 0-based indexing of columns in a projection.
- Column values are returned as an
Option
. However if a column declared as NOT NULL, like EMPLOYEE_ID and LAST_NAME, the result will always beSome
and therefore can be safely unwrapped. - LAST_NAME and FIRST_NAME are retrieved as
&str
. This is fast as they are borrowed directly from the respective column buffers. However those values will only be valid during the lifetime of the row. If the value needs to continue to exist beyond the lifetime of a row, it should be retrieved as aString
.
Oracle Data Types
Sibyl provides API to access several Oracle native data types.
Number
use Number;
let pi = pi;
let two = from_int;
let two_pi = pi.mul?;
let h = from_string?;
let hbar = h.div?;
println!;
Date
use Date;
let apr18_1996 = from_string?;
let next_monday = apr18_1996.next_week_day?;
println!;
Timestamp
There are 3 types of timestamps:
Timestamp
which is equivalent to Oracle TIMESTAMP,TimestampTZ
- TIMESTAMP WITH TIME ZONE,TimestampLTZ
- TIMESTAMP WITH LOCAL TIME ZONE
use TimestampTZ;
let ts = from_string?;
let txt = ts.to_string?;
Interval
There are 2 types of intervals:
IntervalYM
which is eqivalent to Oracle INTERVAL YEAR TO MONTH,IntervalDS
- INTERVAL DAY TO SECOND
use ;
let launch = from_datetime?;
let landing = from_datetime?;
let duration : IntervalDS = landing.subtract?;
assert_eq!;
RowID
Oracle ROWID can be selected and retrieved explicitly into an instance of the RowID
. However, one interesting case is SELECT FOR UPDATE queries where Oracle returns ROWIDs implicitly. Those can be retrieved using Row::get_rowid
method.
let stmt = conn.prepare?;
let rows = stmt.query?;
let cur_row = rows.next?;
assert!;
let row = cur_row.unwrap;
let manager_id: u32 = row.get?.unwrap_or_default;
assert_eq!;
let rowid = row.get_rowid?;
let stmt = conn.prepare?;
let num_updated = stmt.execute?;
assert_eq!;
Cursors
Cursors can be returned explicitly:
let stmt = conn.prepare?;
let mut cursor = new?;
stmt.execute_into?;
let rows = cursor.rows?;
// ...
Or, beginning with Oracle 12.1, implicitly:
let stmt = conn.prepare?;
stmt.execute?;
if let Some = stmt.next_result?
Testing
Some of sibyl's tests connect to the database and expect certain objects to exist in it and certain privileges granted:
- At least the HR demo schema should be installed. If you are using Express Edition, it is already pre-installed.
- While there is no need to install other demo schemas at least
MEDIA_DIR
should be created (see$ORACLE_HOME/demo/schema/mk_dir.sql
) and point to the directory with (a few of) the files that are provided in thedemo/schema/product_media
. - Some of the LOB tests need text files that have to be created manually. Those should be UTF-16 BE encoded without BOM. The hexadecimal dump of the expected content is provided in the respective doc tests.
- A test user should be created. The user needs acccess to the HR schema and to the
MEDIA_DIR
directory. Seeetc/create_sandbox.sql
for an example of how it can be accomplished.
Limitations
At this time sibyl provides only the most commonly needed means to interface with the Oracle database. Some of the missing features are:
- Non-blocking execution
- Array interface for multi-row operations
- User defined data types
- PL/SQL collections and tables
- Objects
- JSON data
- LDAP and proxy authentications
- Global transactions
- Session and connection pooling
- High Availability
- Continuous query and publish-subscribe notifications
- Advanced queuing
- Shards
- Direct path load
Some of these features will be added in the upcoming releases. Some will be likely kept on a backburner until the need arises or they are explicitly requested. And some might never be implemented.