Lookup Table Functions

Lookup table functions serve for lookup and manipulation with lookup tables. (See Lookup Tables.) To use the lookup table function, you need to specify the name of the lookup table as an argument of the lookup() function.

Do not use the functions shown below in the init(), preExecute() or postExecute() functions of CTL template!

It is not possible to have multiple queries to the same lookup table at the same time as there is only one state which holds the next record.

count

lookup(<lookup name>).count(keyValue)

The count() function returns the number of records whose key value equals to keyValue. The count() function used with DB lookup tables may return -1 instead of real count of record with specified key value (if you do not set Max cached size to a non-zero value). The lookup name is simply a name of the lookup table. It is **not **specified as a string enclosed with " character. The keyValue is a value of a key of the lookup table. If the lookup table has a key of one field, keyValue is one string. If the lookup table has a key of more fields, keyValue is specified as series of the values of particular key parts. See the documentation of the particular lookup table for handling of duplicated keys.

Example 334. Usage of count A lookup table with a one-field key.

$out.0.count = lookup(names).count("smithj");

A lookup table with a key of two fields.

$out.0.count = lookup(names).count("John", "Smith");

See also: get, Allow key duplicates

get

lookup(<lookup name>).get(keyValue)[.<field name>|.*]

The function get searches the first record whose key value is equal to the value specified in the get(keyValue) function. It returns the record of the lookup table. You can map it to other records in CTL2 (with the same metadata). If you want to get the value of the field, you can add the . part to the expression or .* to get the values of all fields. If there is no record with the requested keyValue in the lookup table, the function returns null. The keyVal in the function is a sequence of values of the field names separated by comma (not semicolon!). The key has the following form: keyValuePart1,keyValuePart2,…​,keyValuePartN.

Example 335. Usage of get There is a lookup table users having fields name, surname, phone. The key is formed by fields name and surname. The phone of John Smith is acquired by the statement:

$out.0.phone = lookup(users).get("John", "Smith").phone;

You can get the whole record:

UsersMetadata u = lookup(users).get("John", "Smith");

As the get() function returns null if no record is found, getting the whole records allows you to do better error handling.

UsersMetadata u = lookup(users).get("John", "Smith");
if ( ! isnull ( u ) ) {
    $out.0.phone = u.phone;
}

See also: count, next, put

next

lookup(<lookup name>).next()[.<field name>|.*]

The next() function allows you to iterate the result of the search. It moves the pointer to the next record and returns this record. It returns the next record with the same key. If there is no such record, it returns null.

Example 336. Usage of next The basic usage:

Record tmp = lookup(users).next()

The next() function is generally used in combination with get() function:

// Process all records from a lookup
User user = lookup(users).get($in.0.userId);

while ( ! isnull ( user ) ) {
    // Do something with user

    // Grab next user
    user = lookup(users).next();
}

See also: get, isnull

put

lookup(<lookup name>).put(<record>)

The put() function stores the record passed as its argument in the selected lookup table. It returns a boolean result indicating whether the operation has succeeded or not. Note that the metadata of the passed record must match the metadata of the lookup table. The operation may not be supported by all types of lookup tables (it is not supported by Database lookup tables, for example) and its exact semantics is implementation-specific (in particular, the stored records may not be immediately available for reading in the same phase).

Example 337. Usage of put

//Users is a same record as in the lookup table
Users u;
u.name = "John";
u.surname = "Smith";
u.username = "smithj";
lookup(users).put(u);

See also: get,

Example 338. Usage of Lookup Table Functions A UsersLookup lookup table contains Firstname, Surname, and Username columns. Firstname and Surname fields form the key. Lookup all Usernames for each particular Firstname and Surname tuple received from an input port.

//#CTL2

function integer transform() {
    string[] usernames;

    // getting the first record
    // whose key value equals to $in.0.Surname, $in.0.Firstname tuple
    UsersMetadata usersRecord = lookup(UsersLookup).get($in.0.Surname, $in.0.Firstname);

    // iterate through all records found
    while ( ! isnull( usersRecord ) ) {
        usernames = append( usernames, usersRecord.Username);

        // searching the next record with the key specified above
        usersRecord = lookup(UsersLookup).next();
    }

    // mapping to the output
    $out.0.Surname   = $in.0.Surname;
    $out.0.Firstname = $in.0.Firstname;
    $out.0.Username  = usernames;

    return ALL;
}

Remember that DB lookup tables cannot be used in compiled mode. (code starts with the following header: //#CTL2:COMPILE). You need to switch to interpreted mode (with the header: //#CTL2) to be able to access DB lookup tables from CTL2.