perfect-match2.taq

$ java -jar taq.jar perfect-match2

apply_age_rating(Name=John, Age=23, Starsign=gemini, Rating=1.0, Timestamp=2022-09-23T08:00:51.889212Z)
apply_age_rating(Name=Sue, Age=19, Starsign=cancer, Rating=NaN, Timestamp=2022-09-23T08:00:52.050077Z)
apply_age_rating(Name=Sam, Age=34, Starsign=scorpio, Rating=0.3, Timestamp=2022-09-23T08:00:52.172256Z)
apply_age_rating(Name=Jenny, Age=28, Starsign=gemini, Rating=0.6, Timestamp=2022-09-23T08:00:52.306504Z)
apply_age_rating(Name=Andrew, Age=26, Starsign=virgo, Rating=0.6, Timestamp=2022-09-23T08:00:52.440881Z)
apply_age_rating(Name=Alice, Age=20, Starsign=pisces, Rating=1.0, Timestamp=2022-09-23T08:00:52.575231Z)
apply_age_rating(Name=Ingrid, Age=23, Starsign=cancer, Rating=1.0, Timestamp=2022-09-23T08:00:52.698360Z)
apply_age_rating(Name=Jack, Age=32, Starsign=pisces, Rating=0.3, Timestamp=2022-09-23T08:00:52.822988Z)
apply_age_rating(Name=Sonia, Age=33, Starsign=gemini, Rating=0.3, Timestamp=2022-09-23T08:00:52.957377Z)
apply_age_rating(Name=Alex, Age=22, Starsign=aquarius, Rating=1.0, Timestamp=2022-09-23T08:00:53.091543Z)
apply_age_rating(Name=Jill, Age=33, Starsign=cancer, Rating=0.3, Timestamp=2022-09-23T08:00:53.236504Z)
apply_age_rating(Name=Fiona, Age=29, Starsign=gemini, Rating=0.6, Timestamp=2022-09-23T08:00:53.359992Z)
apply_age_rating(Name=Melissa, Age=30, Starsign=virgo, Rating=0.3, Timestamp=2022-09-23T08:00:53.482911Z)
apply_age_rating(Name=Tom, Age=22, Starsign=cancer, Rating=1.0, Timestamp=2022-09-23T08:00:53.606223Z)
apply_age_rating(Name=Bill, Age=19, Starsign=virgo, Rating=NaN, Timestamp=2022-09-23T08:00:53.740342Z)

Description

perfect-match2.taq demonstrates a database resource data collector with an entity class used to define the database records. The “star_people” query creates a dating profile for each person in a database that is 20 years old and over.

The resource declaration does not specify a identifies a provider, so one is selected automatically to use with the H2 database. Only the database file needs to be specified

resource star_people

(database=“db/star-people.db”, type=“H2”) {

When the file is specified with a relative path, as is the case here, then it is located relative to the “workspace” sub directory from where the taq application is launched. The entity class, in double quotes, is referenced using a -> right arrow after the role qualifier

template apply_age_rating

-> “entities_axioms.StarPerson”

As with resource providers, entity classes are external to TAQ and are loaded from the file system on demand.

There are 2 resource operations in the resource declaration body

• star_people.drop_tables() restores the database to an empty state if it exists
• star_people.log_to_console() sends to the console records being written to the database

Note that the above console output shows the rating value of 19 year old Sue and Bill as NaN which is the Java double “not an number” token. SqLite does not natively support the Java double type, so TAQ takes measures to work around this limitation. If you browse the database with a suitable tool, you will see the persisted rating values are encoded.