#database #sql #oracle #oci #ffi

sibyl

An OCI-based driver for Rust applications to interface with Oracle databases

2 releases

✓ Uses Rust 2018 edition

0.1.1 Jun 11, 2019
0.1.0 Jun 10, 2019

#64 in Database interfaces

3 downloads per month

MIT license

394KB
5K SLoC

Sibyl

Sibyl is an OCI-based driver for Rust applications to interface with Oracle databases.

Example

use sibyl as oracle; // pun intended :)

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let oracle = oracle::env()?;
    let conn = oracle.connect("localhost/xepdb1", "sandbox", "password")?;
    let stmt = conn.prepare("
        SELECT first_name, last_name, hire_date
          FROM (
                SELECT first_name, last_name, hire_date
                     , row_number() OVER (ORDER BY hire_date) ord
                  FROM hr.employees
                 WHERE hire_date >= :hire_date
               )
         WHERE ord = 1
    ")?;
    let date = oracle::Date::from_string("January 1, 2005", "MONTH DD, YYYY", &oracle)?;
    let rows = stmt.query(&[ &date ])?;
    // The query returns at most one row, hence the use of `if let` to retrieve it
    if let Some( row ) = rows.next()? {
        // Note that sibyl uses 0-based column indexes.
        // LAST_NAME is retrieved as a &str. This is fast as it borrows directly from
        // the column buffer. However, it will be accessible only within the current
        // scope, i.e. only during the lifetime of the current row.
        // LAST_NAME is NOT NULL, therefore it is safe to simply unwrap it.
        let last_name = row.get::<&str>(0)?.unwrap();
        let name =
            // FIRST_NAME is NULL-able
            if let Some( first_name ) = row.get::<&str>(1)? {
                format!("{}, {}", last_name, first_name)
            } else {
                last_name.to_string()
            }
        ;
        let hire_date = row.get::<oracle::Date>(2)?.unwrap();
        let hire_date = hire_date.to_string("YYYY-MM-DD")?;

        println!("{} was hired {}", name, hire_date);
    } else {
        println!("No one was hired after {}", date.to_string("YYYY-MM-DD")?);
    }
    Ok(())
}

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:

fn main() {
    let oracle = sibyl::env().expect("Oracle OCI environment");
    // ...
}

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 sibyl::Environment;
use lazy_static::lazy_static;

lazy_static!{
    pub static ref ORACLE : Environment = sibyl::env().expect("Oracle OCI environment");
}

Then later one would be able to create, for example, a current timestamp as:

use sibyl::TimestampTZ;

let current_timestamp = TimestampTZ::from_systimestamp(&ORACLE)?;

Connections

Use Environment::connect method to connect to a database:

fn main() {
    let oracle = sibyl::env().expect("Oracle OCI environment");
    let conn = oracle.connect("dbname", "username", "password").expect("New database connection");
    // ...
}

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("
    SELECT employee_id, last_name, first_name
      FROM hr.employees
     WHERE manager_id = :id
  ORDER BY employee_id
")?;

A prepared statement can be executed either with the query or execute or execute_into methods:

  • query is used for SELECT statements. In fact, it will complain if you try to query 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(&[ &103 ])?;

or binding :id by name as:

let rows = stmt.query(&[
    &( ":id", 103 )
])?;

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("
    INSERT INTO hr.departments
           ( department_id, department_name, manager_id, location_id )
    VALUES ( hr.departments_seq.nextval, :department_name, :manager_id, :location_id )
 RETURNING department_id
      INTO :department_id
")?;
let mut department_id: u32 = 0;
let num_inserted = stmt.execute(&[
    &( ":department_name", "Security" ),
    &( ":manager_id",      ""         ),
    &( ":location_id",     1700       ),
], &mut [
    &mut ( ":department_id", &mut department_id )
])?;

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 = HashMap::new();

let rows = stmt.query(&[ &103 ])?;
while let Some( row ) = rows.next()? {
    let employee_id = row.get::<u32>(0)?.unwrap();
    let last_name   = row.get::<&str>(1)?.unwrap();
    let name =
        if let Some( first_name ) = row.get::<&str>(2)? {
            format!("{}, {}", last_name, first_name)
        } else {
            last_name.to_string()
        }
    ;
    employees.insert(employee_id, name);
}

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 be Some 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 a String.

Oracle Data Types

Sibyl provides API to access several Oracle native data types.

Number

use sibyl::Number;

let pi = Number::pi(&oracle);
let two = Number::from_int(2, &oracle);
let two_pi = pi.mul(two)?;
let h = Number::from_string("6.62607004E-34", "9D999999999EEEE", &oracle)?;
let hbar = h.div(two_pi)?;
println!("{}", hbar.to_string("TME")?);

Date

use sibyl::Date;

let apr18_1996 = Date::from_string("18-APR-1996", "DD-MON-YYYY", &oracle)?;
let next_monday = apr18_1996.next_week_day("MONDAY")?;
println!("{}", next_monday.to_string("MM/DD/YYYY")?);

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 sibyl::TimestampTZ;

let ts = oracle::TimestampTZ::from_string(
    "July 20, 1969 8:18:04.16 pm UTC",
    "MONTH DD, YYYY HH:MI:SS.FF PM TZR",
    &oracle
)?;
let txt = ts.to_string("Dy, Mon DD, YYYY HH:MI:SS.FF PM TZR", 3)?;

Interval

There are 2 types of intervals:

  • IntervalYM which is eqivalent to Oracle INTERVAL YEAR TO MONTH,
  • IntervalDS - INTERVAL DAY TO SECOND
use sibyl::{ TimestampTZ, IntervalDS };

let launch = TimestampTZ::from_datetime(1969,7,16,13,32,0,0,"UTC", &oracle)?;
let landing = TimestampTZ::from_datetime(1969,7,24,16,50,35,0,"UTC", &oracle)?;
let duration : IntervalDS = landing.subtract(&launch)?;

assert_eq!("+8 03:18:35.000", duration.to_string(1,3)?);

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("
    SELECT manager_id
      FROM hr.employees
     WHERE employee_id = :id
       FOR UPDATE
")?;
let rows = stmt.query(&[ &107 ])?;
let cur_row = rows.next()?;
assert!(cur_row.is_some());
let row = cur_row.unwrap();

let manager_id: u32 = row.get(0)?.unwrap_or_default();
assert_eq!(103, manager_id);

let rowid = row.get_rowid()?;

let stmt = conn.prepare("
    UPDATE hr.employees
       SET manager_id = :manager_id
     WHERE rowid = :row_id
")?;
let num_updated = stmt.execute(&[
    &( ":manager_id", 102 ),
    &( ":row_id",  &rowid )
])?;
assert_eq!(1, num_updated);

Cursors

Cursors can be returned explicitly:

let stmt = conn.prepare("
    BEGIN
        OPEN :emp FOR
            SELECT department_name, first_name, last_name, salary
              FROM hr.employees e
              JOIN hr.departments d
                ON d.department_id = e.department_id;
    END;
")?;
let mut cursor = Cursor::new(&stmt)?;
stmt.execute_into(&[], &mut [ &mut cursor ])?;
let rows = cursor.rows()?;
// ...

Or, beginning with Oracle 12.1, implicitly:

let stmt = conn.prepare("
    DECLARE
        emp SYS_REFCURSOR;
    BEGIN
        OPEN emp FOR
            SELECT department_name, first_name, last_name, salary
              FROM hr.employees e
              JOIN hr.departments d
                ON d.department_id = e.department_id;
        ;
        DBMS_SQL.RETURN_RESULT(emp);
    END;
")?;
stmt.execute(&[])?;
if let Some( cursor ) = stmt.next_result()? {
    let rows = cursor.rows()?;
    // ...
}

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 the demo/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. See etc/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.

Dependencies

~211KB