HibernateIndexUtil.java

package com.txtr.hibernatedelta.model;

import java.util.ArrayList;
import java.util.List;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

public class HibernateIndexUtil {
    private HibernateIndexUtil() {
    }

    public static List<HibernateIndex> getIndexes(HibernateTable table) {
        List<HibernateIndex> result = new ArrayList<HibernateIndex>();

        List<String> pkColumns = new ArrayList<String>();
        List<String> fkColumns = new ArrayList<String>();

        for (HibernateColumn column : table.getColumns()) {
            if (column.getTargetTable() != null) {
                fkColumns.add(column.getName());
            }

            if (column.isPrimaryKey()) {
                pkColumns.add(column.getName());
            }
        }

        for (ExplicitHibernateIndex index : table.getExplicitIndexes()) {
            result.add(new HibernateIndex(index.getName(), getIndexType(fkColumns, index), index.getColumns()));
        }

        if (!pkColumns.isEmpty()) {
            String firstColumn = pkColumns.get(0);
            String pkIndexName = table.getIndexPrefix() + "0";
            if (pkColumns.size() == 1 && fkColumns.contains(firstColumn)) {
                fkColumns.remove(firstColumn);
                table.getColumn(firstColumn).setIndexName(new HibernateIndexName(pkIndexName, table.getName(), ImmutableList.of(firstColumn)));
                result.add(new HibernateIndex(pkIndexName, HibernateIndexType.JOINED_PRIMARY_KEY, pkColumns));
            } else {
                result.add(new HibernateIndex(pkIndexName, HibernateIndexType.PRIMARY_KEY, pkColumns));
            }
        }

        for (String fkColumn : fkColumns) {
            final HibernateColumn hibernateColumn = table.getColumn(fkColumn);
            result.add(new HibernateIndex(hibernateColumn.getForeignKeyIndexName(), HibernateIndexType.FOREIGN_KEY, ImmutableList.of(fkColumn)));
        }

        filterDominatedIndexes(result);

        return result;
    }

    private static void filterDominatedIndexes(List<HibernateIndex> indexes) {
        for (HibernateIndex index : Lists.newArrayList(indexes)) {
            if (isDominated(indexes, index)) {
                indexes.remove(index);
            }
        }
    }

    private static boolean isDominated(List<HibernateIndex> indexes, HibernateIndex index) {
        for (HibernateIndex longer : indexes) {
            if (isDominated(index.getColumns(), longer.getColumns())) {
                return true;
            }
        }
        return false;
    }

    private static boolean isDominated(List<String> loser, List<String> winner) {
        if (loser.size() >= winner.size()) {
            return false;
        }

        for (int i = 0; i < loser.size(); i++) {
            if (!loser.get(i).equalsIgnoreCase(winner.get(i))) {
                return false;
            }
        }
        return true;
    }

    private static HibernateIndexType getIndexType(List<String> fkColumns, ExplicitHibernateIndex index) {
        // if the first column is an fk column, reuse this as an fk index
        if (fkColumns.contains(index.getColumns().get(0))) {
            fkColumns.remove(index.getColumns().get(0));
            return index.isUnique() ? HibernateIndexType.UNIQUE_FOREIGN_KEY : HibernateIndexType.FOREIGN_KEY;
        }
        if (!index.isUnique()) {
            return HibernateIndexType.NON_UNIQUE;
        }
        return index.isFunctional() ? HibernateIndexType.FUNCTIONAL_UNIQUE : HibernateIndexType.UNIQUE;
    }
}