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SchemaCrawler is an open-source Java API that makes working with database metadata as easy as working with plain old Java objects. SchemaCrawler is also a database schema discovery and comprehension, and schema documentation tool. You can search for database schema objects using regular expressions, and output the schema and data in a readable text format. The output is designed to be diff-ed against other database schemas.

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/*
========================================================================
SchemaCrawler
http://www.schemacrawler.com
Copyright (c) 2000-2016, Sualeh Fatehi .
All rights reserved.
------------------------------------------------------------------------

SchemaCrawler is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SchemaCrawler and the accompanying materials are made available under
the terms of the Eclipse Public License v1.0, GNU General Public License
v3 or GNU Lesser General Public License v3.

You may elect to redistribute this code under any of these licenses.

The Eclipse Public License is available at:
http://www.eclipse.org/legal/epl-v10.html

The GNU General Public License v3 and the GNU Lesser General Public
License v3 are available at:
http://www.gnu.org/licenses/

========================================================================
*/
package schemacrawler.crawl;


import static java.util.Objects.requireNonNull;

import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import java.util.function.Predicate;

import schemacrawler.schema.ForeignKey;
import schemacrawler.schema.ForeignKeyColumnReference;
import schemacrawler.schema.PartialDatabaseObject;
import schemacrawler.schema.Reducer;
import schemacrawler.schema.Table;
import schemacrawler.schema.TableRelationshipType;
import schemacrawler.schemacrawler.SchemaCrawlerOptions;

public class TablesReducer
  implements Reducer
{

  private final SchemaCrawlerOptions options;
  private final Predicate tableFilter;

  public TablesReducer(final SchemaCrawlerOptions options,
                       final Predicate tableFilter)
  {
    this.options = requireNonNull(options);
    this.tableFilter = requireNonNull(tableFilter);
  }

  @Override
  public void reduce(final Collection allTables)
  {
    if (allTables == null)
    {
      return;
    }
    allTables.retainAll(doReduce(allTables));

    removeForeignKeys(allTables);
  }

  private Collection doReduce(final Collection allTables)
  {
    // Filter tables, keeping the ones we need
    final Set reducedTables = new HashSet<>();
    for (final Table table: allTables)
    {
      if (tableFilter.test(table))
      {
        reducedTables.add(table);
      }
    }

    // Add in referenced tables
    final int childTableFilterDepth = options.getChildTableFilterDepth();
    final Collection childTables = includeRelatedTables(TableRelationshipType.child,
                                                               childTableFilterDepth,
                                                               reducedTables);
    final int parentTableFilterDepth = options.getParentTableFilterDepth();
    final Collection parentTables = includeRelatedTables(TableRelationshipType.parent,
                                                                parentTableFilterDepth,
                                                                reducedTables);

    final Set keepTables = new HashSet<>();
    keepTables.addAll(reducedTables);
    keepTables.addAll(childTables);
    keepTables.addAll(parentTables);

    // Mark tables as being filtered out
    for (final Table table: allTables)
    {
      if (isTablePartial(table) || !keepTables.contains(table))
      {
        markTableFilteredOut(table);
      }
    }

    return keepTables;
  }

  private Collection includeRelatedTables(final TableRelationshipType tableRelationshipType,
                                                 final int depth,
                                                 final Set greppedTables)
  {
    final Set includedTables = new HashSet<>();
    includedTables.addAll(greppedTables);

    for (int i = 0; i < depth; i++)
    {
      for (final Table table: new HashSet<>(includedTables))
      {
        for (final Table relatedTable: table
          .getRelatedTables(tableRelationshipType))
        {
          if (!isTablePartial(relatedTable))
          {
            includedTables.add(relatedTable);
          }
        }
      }
    }

    return includedTables;
  }

  private boolean isTablePartial(final Table table)
  {
    return table instanceof PartialDatabaseObject;
  }

  private void markTableFilteredOut(final Table referencedTable)
  {
    referencedTable.setAttribute("schemacrawler.table.filtered_out", true);
    if (options.isGrepOnlyMatching())
    {
      referencedTable.setAttribute("schemacrawler.table.no_grep_match", true);
    }
  }

  private void removeForeignKeys(final Collection allTables)
  {
    for (final Table table: allTables)
    {
      for (final ForeignKey foreignKey: table.getExportedForeignKeys())
      {
        for (final ForeignKeyColumnReference fkColumnRef: foreignKey)
        {
          final Table referencedTable = fkColumnRef.getForeignKeyColumn()
            .getParent();
          if (isTablePartial(referencedTable)
              || !allTables.contains(referencedTable))
          {
            markTableFilteredOut(referencedTable);
          }
        }
      }
    }
  }

}




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