Group Move With Hint Strategies

Moves a related set of objects together, guided by per-group hint strategies. When a partition has many groups, each with its own constraints, trying every possible combination is intractable. Instead, this move type lets you hint which strategy to try for each group, so it only evaluates moves that are known to be feasible for that group.

Parameters

Parameter	Type	Required	Default	Description
primaryPartition	string	Yes	-	The outer partition
secondaryPartition	string	Yes	-	The inner partition that splits the primary partition
moveStrategies	MoveStrategies	Yes	-	The hint strategies to try for each group
unassignedContainer	string	No	-	If set, an allocated secondary group may be replaced by a different secondary group drawn from this container
secondaryGroupReplacementConfig	SecondaryGroupReplacementConfig	No	-	Restricts, per secondary group, which other secondary groups may replace it (only used when unassignedContainer is set)

Behavior

Given a partition whose groups each have unique constraints, the move type applies a different move strategy per group according to the supplied hints. Each strategy generates one or more candidate move sets; all generated move sets are compared, and the best resulting one is applied. By relying on the hints, the move type skips combinations that are known to be infeasible, drastically shrinking the search space compared to a brute-force exploration.

Complexity

Roughly T * N * S * K single-move evaluations, where T is the number of primary groups, N the average number of objects per (primary, secondary) group, S the number of secondary groups, and K the number of move sets generated per group.

Example

Configure local search to use only the group move with hint strategies move type:

GroupMoveWithHintStrategiesMoveTypeSpec groupMove;
groupMove.primaryPartition() = "table";
groupMove.secondaryPartition() = "shard_type";
// moveStrategies supplies the per-group hint strategies to try.

LocalSearchSolverSpec localSearch;
localSearch.moveTypeList()->push_back(
    ProblemSolver::makeMoveTypeSpec(groupMove));

solver.addSolver(localSearch);

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