make_resource

Type of operation: Metadata

Description

Creates a Resource dataset from an input Event or Interval dataset. make_resource must specify a primary key when the verb input dataset has none. If no primary key is specified, the input’s primary key will be used in the output.

For Event datasets, make_resource collapses adjacent events that contain the same primary key value and column values, and uses the first time such event is observed as Valid From. The end result is a dataset that stores snapshots of the state of the observed entity, as a resource.

For Interval datasets, make_resource will behave as though the input is an Event dataset whose timestamp column is the “Valid From” column, and the “Valid To” column will be used as a default validfor.

The Valid To of the row is determined by the minimal of the following three things:

1. the timestamp of the next distinct event

2. Valid From + the expression optionally specified in validfor

3. Valid From + the expiry option value.

If an expiry value is not provided, the default is 24 hours (86,400 seconds.)

Using the expiry option costs less than using the more flexible validfor argument. If you can live with a constant maximum resource lifetime, using something like options(expiry:24h) is the most efficient option.

Note that make_resource cannot be used to directly convert a Table dataset to a Resource dataset. To do this, first convert the Table dataset to an Event dataset using make_event or to an Interval dataset using make_interval, and then you can use make_resource.

Behavior of make_resource verb when handling events with same key arriving at the same time is undefined. Current implementation will handle them in a best effort manner, and merge the events by picking a random non-null values for each column.

Usage

make_resource [ options ], [ columnbinding_1, columnbinding_2, ... ], [ primarykey ], [ validfor ]

Argument	Type	Optional	Repeatable	Restrictions
options	options	yes	no	constant
columnbinding	expression	yes	yes	none
primarykey	primarykey	yes	no	none
validfor	validfor	yes	no	none

Options

Option	Type	Meaning
expiry	duration	How long a Resource lifetime is extended after an observed state change.

Accelerable

make_resource is always accelerable if the input is accelerable. A dataset that only uses accelerable verbs can be accelerated, making queries on the dataset respond faster.

Examples

make_resource options(expiry:duration_hr(1)), col1:col1, primary_key(pk1, pk2)

From the input Event dataset, creates a Resource dataset with the primary key (pk1, pk2) and column col1 with an expiry period of 1 hour.

make_resource col1:col1, primary_key(pk1, pk2), valid_for(duration(col2))

From the input Event dataset, creates a Resource dataset with the primary key (pk1, pk2) and column col1 with an expiry period determined by column col2.

make_resource col1:col1, primary_key(pk1, pk2)

From the input Interval dataset, creates a Resource dataset with the primary key (pk1, pk2) and column col1 with an expiry period determined by the input dataset’s “Valid To” column.

make_resource col1:col1

Assume the verb input is an Event dataset with a primary key (pk1, pk2) and additional columns col1 and col2. The above OPAL creates a Resource dataset with the primary key (pk1, pk2) and column col1 with the default 24-hour expiry period. Notice that the input primary key is propagated to the output, since there is no primary_key clause.

make_resource col1:col1, primary_key(pk1)

Assume the verb input is an Event dataset with a primary key (pk1, pk2) and additional columns col1 and col2. The above OPAL creates a Resource dataset with the primary key (pk1) and column col1 with the default 24-hour expiry period. Notice that the primary_key clause overrides the primary key of the verb’s input dataset.

Aliases

• makeresource (deprecated)