@Override
public String exec(Tuple input) throws IOException {
    if (input == null) {
        warn("Input to LogIndex is null", PigWarning.UDF_WARNING_1);
        return null;
    }

    HashMap<String, Integer> logFields;
    String field = "";
    String logType = "";
    int logTypeIdx = 0;

    try {
        // Shift logType index to 1 if source tagging is used
        // This is because filename is prepended at 0th index
        if(isSourceTaggingUsed)
            logTypeIdx = 1;
        logType = input.get(logTypeIdx).toString();
        if (logSchema == null) {
            // Read the file, open as a local file
            logSchema = MNMLogParser.parseLogMetadata(this.logTransformsManager.getTransformsConfLoadPath());
        }
        logFields = logSchema.get(logType);
        field = input.get(input.size() - 1).toString();
        // Index of field in the schema
        Object idx = logFields.get(field.toLowerCase());

        // Look in the Key-Value part of log line if the field
        // is not a part of transforms.conf
        if(null == idx) {
            // Assumption: KeyValue part always appears as the last part of log line
            String keyValLine = input.get(input.size() - 2).toString();
            return MNMLogParser.parseKeyValue(keyValLine, field);
        }

        int intIdx = ((Integer)idx).intValue();
        // Increment the element's position if source tagging is used
        if(isSourceTaggingUsed) {
            intIdx++;
        }

        Object val = input.get(intIdx);

        return val.toString();

    } catch (IndexOutOfBoundsException ie) {
        String msg = "Field is : " + field + " logType is :" + logType;
        warn(msg + " --> " + ie.toString(), PigWarning.UDF_WARNING_2);
        return null;
    } catch (NullPointerException npe) {
        warn(npe.toString(), PigWarning.UDF_WARNING_3);
        return null;
    }
}