DECIDE queries

In DeQL, a DECIDE statement tells Decisionhouse what to choose from a candidate set.

DECIDE INTO knapsack
FROM items
DECISION COLUMNS (
  is_selected INTEGER BETWEEN 0 AND 1
)
SUBJECT TO
  CONSTRAINT budget: SUM(weight * is_selected) <= 25
MAXIMIZE SUM(value * is_selected);

Statement anatomy

Clause	Purpose
`DECIDE INTO knapsack`	Names the result
`FROM items`	Selects a candidate set
`DECISION COLUMNS (...)`	Declares the unknown values
`SUBJECT TO`	Lists constraints, separated by commas
`MAXIMIZE` or `MINIMIZE`	Defines one objective

FROM must name a candidate set. It cannot name a raw source table.

Decision columns

Each decision column becomes a new column in the result. Its value is selected by the solver for each candidate row.

DECISION COLUMNS (
  is_selected INTEGER BETWEEN 0 AND 1
)

A decision column cannot reuse the name of a column already present in the candidate set.

Constraints

Aggregate across candidates with SUM(...).

CONSTRAINT budget: SUM(weight * is_selected) <= 25

A constraint without SUM(...) applies to every row individually.

CONSTRAINT per_item_limit: allocation <= available

Supported constraint senses are <=, >=, and =. The right-hand side may be a literal or a candidate column.

Grouped constraints

Use BY (...) to repeat an aggregate constraint for each group.

SUBJECT TO
  CONSTRAINT capacity:
    SUM(gpus) <= capacity BY (pool_id),
  CONSTRAINT demand:
    SUM(gpus) = demand BY (workload_id)

The first constraint limits each pool independently. The second satisfies each workload independently.

Objectives

A query has one linear objective.

MAXIMIZE SUM(value * is_selected)

Sums can be added and subtracted, and the expression may include a constant term.

MAXIMIZE
  SUM(value * pick)
  - SUM(DISTINCT fixed_cost * open)

For a decision column grouped with BY, SUM(DISTINCT ...) counts its single group value once instead of repeating it for every candidate row in that group.

See grouped constraints in practice Build a GPU allocation model over pool and workload pairs.