Massive provides visibility and functionality for certain database structures beyond the standard set of tables, (ordinary) views, and functions.
Like standard views, materialized views are essentially a name attached to a
SELECT query. Unlike standard views, materialized views store their results instead of executing the underlying query each time they're invoked. This makes materialized views a lot faster, but means they won't always reflect the latest information.
Refreshing Materialized Views
Materialized views must be refreshed whenever you need to ensure the information in them is up to date.
Materialized views ordinarily block reads while refreshing. To avoid this, invoke the function passing
true to specify a concurrent refresh.
refresh yields an empty query result.
await db.cached_statistics.refresh(true); // concurrently
An enumeration is a data type which represents one of a fixed set of text values. They can make convenient replacements for lookup tables, so long as existing values are truly fixed (values may be added but not removed).
Enums are loaded on startup and can be accessed through the
db.enums.myenum; // -> ['one', 'two', 'three'];
Note that if you add new values to the enum you must either separately append them to
db.enums or invoke
db.reload() to stay up to date.
Sequences are the counters which back up
BIGSERIAL columns. When used as table primary keys, sequences operate transparently and give their next values to rows as they're inserted. However, sequences can also be used independently, in which case it can be useful to know certain things about their state.
Massive only loads independent sequences and ignores those belonging to table primary keys.
lastValue returns the current value of the sequence counter. This value may not actually reside anywhere in the database! When a sequence is incremented, its value is reserved even if the transaction which caused the incrementation aborts.
const val = await db.mysequence.lastValue();
nextValue increments the sequence counter and returns the latest value.
const val = await db.mysequence.nextValue();
reset starts the sequence over at 1 (if called without arguments) or a value of your choosing.
// the next value acquired from the sequence will be 123. await db.mysequence.reset(123);