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/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.command.ddl;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import org.h2.api.ErrorCode;
import org.h2.command.CommandInterface;
import org.h2.constraint.Constraint;
import org.h2.constraint.ConstraintActionType;
import org.h2.engine.Database;
import org.h2.engine.Right;
import org.h2.engine.SessionLocal;
import org.h2.message.DbException;
import org.h2.schema.Schema;
import org.h2.table.MaterializedView;
import org.h2.table.Table;
import org.h2.table.TableView;
import org.h2.util.Utils;
/**
* This class represents the statement
* DROP TABLE
*/
public class DropTable extends DefineCommand {
private boolean ifExists;
private ConstraintActionType dropAction;
private final ArrayList tables = Utils.newSmallArrayList();
public DropTable(SessionLocal session) {
super(session);
dropAction = getDatabase().getSettings().dropRestrict ?
ConstraintActionType.RESTRICT :
ConstraintActionType.CASCADE;
}
public void setIfExists(boolean b) {
ifExists = b;
}
/**
* Add a table to drop.
*
* @param schema the schema
* @param tableName the table name
*/
public void addTable(Schema schema, String tableName) {
tables.add(new SchemaAndTable(schema, tableName));
}
private boolean prepareDrop() {
HashSet tablesToDrop = new HashSet<>();
for (SchemaAndTable schemaAndTable : tables) {
String tableName = schemaAndTable.tableName;
Table table = schemaAndTable.schema.findTableOrView(session, tableName);
if (table == null) {
if (!ifExists) {
throw DbException.get(ErrorCode.TABLE_OR_VIEW_NOT_FOUND_1, tableName);
}
} else {
session.getUser().checkTableRight(table, Right.SCHEMA_OWNER);
if (!table.canDrop()) {
throw DbException.get(ErrorCode.CANNOT_DROP_TABLE_1, tableName);
}
tablesToDrop.add(table);
}
}
if (tablesToDrop.isEmpty()) {
return false;
}
for (Table table : tablesToDrop) {
ArrayList dependencies = new ArrayList<>();
if (dropAction == ConstraintActionType.RESTRICT) {
CopyOnWriteArrayList dependentViews = table.getDependentViews();
if (dependentViews != null && !dependentViews.isEmpty()) {
for (TableView v : dependentViews) {
if (!tablesToDrop.contains(v)) {
dependencies.add(v.getName());
}
}
}
CopyOnWriteArrayList dependentMaterializedViews = table
.getDependentMaterializedViews();
if (dependentMaterializedViews != null && !dependentMaterializedViews.isEmpty()) {
for (MaterializedView v : dependentMaterializedViews) {
if (!tablesToDrop.contains(v)) {
dependencies.add(v.getName());
}
}
}
final List constraints = table.getConstraints();
if (constraints != null && !constraints.isEmpty()) {
for (Constraint c : constraints) {
if (!tablesToDrop.contains(c.getTable())) {
dependencies.add(c.getName());
}
}
}
if (!dependencies.isEmpty()) {
throw DbException.get(ErrorCode.CANNOT_DROP_2, table.getName(),
String.join(", ", new HashSet<>(dependencies)));
}
}
table.lock(session, Table.EXCLUSIVE_LOCK);
}
return true;
}
private void executeDrop() {
for (SchemaAndTable schemaAndTable : tables) {
// need to get the table again, because it may be dropped already
// meanwhile (dependent object, or same object)
Table table = schemaAndTable.schema.findTableOrView(session, schemaAndTable.tableName);
if (table != null) {
table.setModified();
Database db = getDatabase();
db.lockMeta(session);
db.removeSchemaObject(session, table);
}
}
}
@Override
public long update() {
if (prepareDrop()) {
executeDrop();
}
return 0;
}
public void setDropAction(ConstraintActionType dropAction) {
this.dropAction = dropAction;
}
@Override
public int getType() {
return CommandInterface.DROP_TABLE;
}
private static final class SchemaAndTable {
final Schema schema;
final String tableName;
SchemaAndTable(Schema schema, String tableName) {
this.schema = schema;
this.tableName = tableName;
}
}
}
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