RowStoreFetchChecker.java

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package org.apache.doris.nereids.util;

import org.apache.doris.catalog.Column;
import org.apache.doris.nereids.trees.expressions.Slot;
import org.apache.doris.nereids.trees.expressions.SlotReference;

import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

/** Utility to determine whether FE can safely request row-store lazy fetch on BE. */
public final class RowStoreFetchChecker {
    private RowStoreFetchChecker() {
    }

    /**
     * Check if we can use row-store lazy fetch for the given lazy slots. The check is based on the following criteria:
     */
    public static boolean canUseRowStoreForLazySlots(List<Slot> lazySlots) {
        Set<Integer> originalColumnUniqueIds = new HashSet<>();
        for (Slot lazySlot : lazySlots) {
            if (!(lazySlot instanceof SlotReference)) {
                return false;
            }
            SlotReference slotReference = (SlotReference) lazySlot;
            // BE row-store fetch maps values only by col_unique_id and does not carry sub-column paths.
            if (slotReference.hasSubColPath()) {
                return false;
            }
            Optional<Column> originalColumn = slotReference.getOriginalColumn();
            if (!originalColumn.isPresent() || !originalColumnUniqueIds.add(originalColumn.get().getUniqueId())) {
                return false;
            }
        }
        return true;
    }
}