class IgniteHashIndexSpool extends Spool implements IgniteRel {
    /** Search row. */
    private final List<RexNode> searchRow;

    /** Keys (number of the columns at the input row) to build hash index. */
    private final ImmutableBitSet keys;

    /** Filters. */
    private final RexNode cond;

    /** Allow NULL values. */
    private final boolean allowNulls;

    /** */
    public IgniteHashIndexSpool(
        RelOptCluster cluster,
        RelTraitSet traits,
        RelNode input,
        List<RexNode> searchRow,
        RexNode cond,
        boolean allowNulls
    ) {
        super(cluster, traits, input, Type.LAZY, Type.EAGER);

        assert !F.isEmpty(searchRow);

        this.searchRow = searchRow;
        this.cond = cond;
        this.allowNulls = allowNulls;

        keys = ImmutableBitSet.of(RexUtils.notNullKeys(searchRow));
    }

    /**
     * Constructor used for deserialization.
     *
     * @param input Serialized representation.
     */
    public IgniteHashIndexSpool(RelInput input) {
        this(input.getCluster(),
            input.getTraitSet().replace(IgniteConvention.INSTANCE),
            input.getInputs().get(0),
            input.getExpressionList("searchRow"),
            input.getExpression("condition"),
            input.getBoolean("allowNulls", false)
        );
    }

    /** {@inheritDoc} */
    @Override public <T> T accept(IgniteRelVisitor<T> visitor) {
        return visitor.visit(this);
    }

    /** */
    @Override public IgniteRel clone(RelOptCluster cluster, List<IgniteRel> inputs) {
        return new IgniteHashIndexSpool(cluster, getTraitSet(), inputs.get(0), searchRow, cond, allowNulls);
    }

    /** {@inheritDoc} */
    @Override protected Spool copy(RelTraitSet traitSet, RelNode input, Type readType, Type writeType) {
        return new IgniteHashIndexSpool(getCluster(), traitSet, input, searchRow, cond, allowNulls);
    }

    /** {@inheritDoc} */
    @Override public boolean isEnforcer() {
        return true;
    }

    /** */
    @Override public RelWriter explainTerms(RelWriter pw) {
        RelWriter writer = super.explainTerms(pw);

        return writer
            .item("searchRow", searchRow)
            .item("condition", cond)
            .item("allowNulls", allowNulls);
    }

    /** {@inheritDoc} */
    @Override public RelOptCost computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {<FILL_FUNCTION_BODY>}

    /** {@inheritDoc} */
    @Override public double estimateRowCount(RelMetadataQuery mq) {
        return mq.getRowCount(getInput()) * mq.getSelectivity(this, null);
    }

    /** */
    public List<RexNode> searchRow() {
        return searchRow;
    }

    /** */
    public ImmutableBitSet keys() {
        return keys;
    }

    /** */
    public RexNode condition() {
        return cond;
    }

    /** */
    public boolean allowNulls() {
        return allowNulls;
    }
}

        double rowCnt = mq.getRowCount(getInput());
        double bytesPerRow = getRowType().getFieldCount() * IgniteCost.AVERAGE_FIELD_SIZE;
        double totalBytes = rowCnt * bytesPerRow;
        double cpuCost = IgniteCost.HASH_LOOKUP_COST;

        IgniteCostFactory costFactory = (IgniteCostFactory)planner.getCostFactory();

        return costFactory.makeCost(rowCnt, cpuCost, 0, totalBytes, 0);
    
<no_super_class>