M2M AD301 Guia do Utilizador descarregar pdf (Página 127)

Data Integration with Sybase Avaki Studio 115

Custom

algorithm with the second input result set as the inner table. This would produce a

result set consisting of:

— ACCT_NO - the account number for the transaction

— SYMBOL - the symbol of the stock purchased

— NO_OF_SHARES - the number of shares of stock purchased

— COST - the cost per share

— CURRENCY - the currency in which COST is expressed (from the first input)

— CURRENCY - the currency for which the conversion factor applies (from the

second input)

— MULTIPLIER - the factor by which the original value is multiplied to get the

Euro value

You could then use a Projection operator to remove the unneeded columns and to

compute the COST_IN_EURO column (the formula being NO_OF_SHARES * COST *

MULTIPLIER

Solving the problem with a Custom operator

An alternative implementation for this same functionality is to use a Custom operator

to build a lookup table that maps currency to multiplier and then performs the compu-

tation as you read in the account result set.

Note This technique is presented here to illustrate, using a relatively simple

problem, how to use Custom operators—not necessarily as a recommendation

for best practices.

This example uses a .jsi file as well as a Custom operator. The .jsi file contains the fol-

lowing JavaScript:

var lookupTable = {}; // This will contain the mapping of currency type to

conversion factor.

function setUpLookupTable(rs) {

if (lookupTable.initialized == true) {

return; // We only need to read the result set into the map once

}

while (rs.next()) { // Iterate over the rows in the result set

var key = rs.getString(rs, "CURRENCY"); // Get the currency type

var value = rs.getRealValue("MULTIPLIER"); // Get the conversion factor

lookupTable[key] = value; // Save the key/value pair

}

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M2M AD301 Guia do Utilizador Página 127