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package com.vladmihalcea.hibernate.id;
import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.boot.model.relational.Database;
import org.hibernate.boot.model.relational.QualifiedNameParser;
import org.hibernate.boot.model.relational.SqlStringGenerationContext;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.jdbc.env.spi.JdbcEnvironment;
import org.hibernate.engine.jdbc.spi.JdbcCoordinator;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
import org.hibernate.id.Configurable;
import org.hibernate.id.IdentifierGenerationException;
import org.hibernate.id.PersistentIdentifierGenerator;
import org.hibernate.id.enhanced.DatabaseStructure;
import org.hibernate.id.enhanced.Optimizer;
import org.hibernate.id.enhanced.SequenceStructure;
import org.hibernate.internal.util.config.ConfigurationHelper;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.type.Type;
import java.io.Serializable;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* A sequence generator that uses a recursive query to fetch multiple
* values from a sequence in a single database access.
*
* Parameters
* The following configuration parameters are supported:
*
* - {@value #SEQUENCE_PARAM}
* - mandatory, name of the sequence to use
* - {@value #FETCH_SIZE_PARAM}
* - optional, how many sequence numbers should be fetched at a time,
* default is {@value #DEFAULT_FETCH_SIZE}
*
*
* SQL
* Per default the generated SELECT will look something like this
*
* WITH RECURSIVE t(n) AS (
* SELECT 1
* UNION ALL
* SELECT n + 1
* FROM t
* WHERE n < ?)
* SELECT nextval(seq_xxx)
* FROM t;
*
*
* DB2
* For DB2 the generated SELECT will look something like this
*
* WITH t(n) AS (
* SELECT 1 AS n
* FROM (VALUES 1)
* UNION ALL
* SELECT n + 1 AS n
* FROM t
* WHERE n < ?)
* SELECT next value for SEQ_CHILD_ID AS n
* FROM t;
*
*
* HSQLDB
* For HSQLDB the generated SELECT will look something like this
*
* SELECT next value for seq_parent_id
* FROM UNNEST(SEQUENCE_ARRAY(1, ?, 1));
*
*
* Oracle
* For Oracle the generated SELECT will look something like this
* because Oracle does not support using recursive common table
* expressions to fetch multiple values from a sequence.
*
* SELECT seq_xxx.nextval
* FROM dual
* CONNECT BY rownum <= ?
*
*
* SQL Server
* For SQL Server the generated SELECT will look something like this
*
* WITH t(n) AS (
* SELECT 1 AS n
* UNION ALL
* SELECT n + 1 AS n
* FROM t
* WHERE n < ?)
* SELECT NEXT VALUE FOR seq_xxx AS n
* FROM t
*
*
* Firebird
* For Firebird the generated SELECT will look something like this
*
* WITH RECURSIVE t(n, level_num) AS (
* SELECT NEXT VALUE FOR seq_xxx AS n, 1 AS level_num
* FROM rdb$database
* UNION ALL
* SELECT NEXT VALUE FOR seq_xxx AS n, level_num + 1 AS level_num
* FROM t
* WHERE level_num < ?)
* SELECT n
* FROM t
*
*
* Database Support
* The following RDBMS have been verified to work
*
* - DB2
* - Firebird
* - Oracle
* - H2
* - HSQLDB
* - MariaDB
* - Postgres
* - SQL Sever
*
*
* In theory any RDBMS that supports {@code WITH RECURSIVE} and
* sequences is supported.
*
* For more details about how to use it, check out this article on vladmihalcea.com.
*
* @author Philippe Marschall
* @since 2.14.0
*/
public class BatchSequenceGenerator implements BulkInsertionCapableIdentifierGenerator, PersistentIdentifierGenerator, Configurable {
/**
* Indicates the name of the sequence to use, mandatory.
*/
public static final String SEQUENCE_PARAM = "sequence";
/**
* Indicates how many sequence values to fetch at once. The default value is {@link #DEFAULT_FETCH_SIZE}.
*/
public static final String FETCH_SIZE_PARAM = "fetch_size";
/**
* The default value for {@link #FETCH_SIZE_PARAM}.
*/
public static final int DEFAULT_FETCH_SIZE = 10;
private final Lock lock = new ReentrantLock();
private String select;
private int fetchSize;
private IdentifierPool identifierPool;
private IdentifierExtractor identifierExtractor;
private DatabaseStructure databaseStructure;
@Override
public void configure(Type type, Properties params, ServiceRegistry serviceRegistry)
throws MappingException {
JdbcEnvironment jdbcEnvironment = serviceRegistry.getService(JdbcEnvironment.class);
Dialect dialect = jdbcEnvironment.getDialect();
String sequenceName = determineSequenceName(params);
this.fetchSize = determineFetchSize(params);
this.select = buildSelect(sequenceName, dialect);
this.identifierExtractor = IdentifierExtractor.getIdentifierExtractor(type.getReturnedClass());
this.identifierPool = IdentifierPool.empty();
this.databaseStructure = this.buildDatabaseStructure(type, sequenceName, jdbcEnvironment);
}
private static String buildSelect(String sequenceName, Dialect dialect) {
if (dialect instanceof org.hibernate.dialect.OracleDialect) {
return "SELECT " + dialect.getSequenceSupport().getSelectSequenceNextValString(sequenceName) + " FROM dual CONNECT BY rownum <= ?";
}
if (dialect instanceof org.hibernate.dialect.SQLServerDialect) {
// No RECURSIVE
return "WITH t(n) AS ( "
+ "SELECT 1 AS n "
+ "UNION ALL "
+"SELECT n + 1 AS n FROM t WHERE n < ?) "
// sequence generation outside of WITH
+ "SELECT " + dialect.getSequenceSupport().getSelectSequenceNextValString(sequenceName) + " AS n FROM t";
}
if (dialect instanceof org.hibernate.dialect.DB2Dialect) {
// No RECURSIVE
return "WITH t(n) AS ( "
+ "SELECT 1 AS n "
// difference
+ "FROM (VALUES 1) "
+ "UNION ALL "
+"SELECT n + 1 AS n FROM t WHERE n < ?) "
// sequence generation outside of WITH
+ "SELECT " + dialect.getSequenceSupport().getSelectSequenceNextValString(sequenceName) + " AS n FROM t";
}
if (dialect instanceof org.hibernate.dialect.HSQLDialect) {
// https://stackoverflow.com/questions/44472280/cte-based-sequence-generation-with-hsqldb/52329862
return "SELECT " + dialect.getSequenceSupport().getSelectSequenceNextValString(sequenceName) + " FROM UNNEST(SEQUENCE_ARRAY(1, ?, 1))";
}
return "WITH RECURSIVE t(n) AS ("
+ "SELECT 1 "
+ "UNION ALL "
+ "SELECT n + 1"
+ " FROM t "
+ " WHERE n < ?) "
+ "SELECT " + dialect.getSequenceSupport().getSelectSequenceNextValString(sequenceName) + " FROM t";
}
private SequenceStructure buildDatabaseStructure(Type type, String sequenceName, JdbcEnvironment jdbcEnvironment) {
return new SequenceStructure(jdbcEnvironment, "orm",
QualifiedNameParser.INSTANCE.parse(sequenceName), 1, 1, type.getReturnedClass());
}
private static String determineSequenceName(Properties params) {
String sequenceName = params.getProperty(SEQUENCE_PARAM);
if (sequenceName == null) {
throw new MappingException("no squence name specified");
}
return sequenceName;
}
private static int determineFetchSize(Properties params) {
int fetchSize = ConfigurationHelper.getInt(FETCH_SIZE_PARAM, params, DEFAULT_FETCH_SIZE);
if (fetchSize <= 0) {
throw new MappingException("fetch size must be positive");
}
return fetchSize;
}
@Override
public boolean supportsBulkInsertionIdentifierGeneration() {
return true;
}
@Override
public String determineBulkInsertionIdentifierGenerationSelectFragment(SqlStringGenerationContext sqlStringGenerationContext) {
return sqlStringGenerationContext.getDialect().getSequenceSupport().getSequenceNextValString(this.getSequenceName());
}
@Override
public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
this.lock.lock();
try {
if (this.identifierPool.isEmpty()) {
this.identifierPool = this.replenishIdentifierPool(session);
}
return this.identifierPool.next();
} finally {
this.lock.unlock();
}
}
private String getSequenceName() {
return this.databaseStructure.getPhysicalName().render();
}
@Override
public void registerExportables(Database database) {
this.databaseStructure.registerExportables(database);
}
private IdentifierPool replenishIdentifierPool(SharedSessionContractImplementor session)
throws HibernateException {
JdbcCoordinator coordinator = session.getJdbcCoordinator();
List identifiers = new ArrayList<>(this.fetchSize);
try (PreparedStatement statement = coordinator.getStatementPreparer().prepareStatement(this.select)) {
statement.setFetchSize(this.fetchSize);
statement.setInt(1, this.fetchSize);
try (ResultSet resultSet = coordinator.getResultSetReturn().extract(statement)) {
while (resultSet.next()) {
identifiers.add(this.identifierExtractor.extractIdentifier(resultSet));
}
}
} catch (SQLException e) {
throw session.getJdbcServices().getSqlExceptionHelper().convert(
e, "could not get next sequence value", this.select);
}
if (identifiers.size() != this.fetchSize) {
throw new IdentifierGenerationException("expected " + this.fetchSize + " values from " + this.getSequenceName()
+ " but got " + identifiers.size());
}
return IdentifierPool.forList(identifiers);
}
@Override
public Optimizer getOptimizer() {
return null;
}
/**
* Holds a number of prefetched identifiers.
*/
static final class IdentifierPool {
private final Iterator iterator;
private IdentifierPool (List identifiers) {
this.iterator = identifiers.iterator();
}
static IdentifierPool forList(List identifiers) {
return new IdentifierPool(identifiers);
}
static IdentifierPool empty() {
return new IdentifierPool(Collections.emptyList());
}
boolean isEmpty() {
return !this.iterator.hasNext();
}
Serializable next() {
return this.iterator.next();
}
}
/**
* Extracts a {@link Serializable} identifier from a {@link ResultSet}.
*
* @see org.hibernate.id.IntegralDataTypeHolder
*/
enum IdentifierExtractor {
INTEGER_IDENTIFIER_EXTRACTOR {
@Override
Serializable extractIdentifier(ResultSet resultSet) throws SQLException {
int intValue = resultSet.getInt(1);
if (resultSet.wasNull()) {
throw new IdentifierGenerationException("sequence returned null");
}
return intValue;
}
},
LONG_IDENTIFIER_EXTRACTOR {
@Override
Serializable extractIdentifier(ResultSet resultSet) throws SQLException {
long longValue = resultSet.getLong(1);
if (resultSet.wasNull()) {
throw new IdentifierGenerationException("sequence returned null");
}
return longValue;
}
},
BIG_INTEGER_IDENTIFIER_EXTRACTOR {
@Override
Serializable extractIdentifier(ResultSet resultSet) throws SQLException {
BigDecimal bigDecimal = resultSet.getBigDecimal(1);
if (resultSet.wasNull()) {
throw new IdentifierGenerationException("sequence returned null");
}
return bigDecimal.setScale(0, BigDecimal.ROUND_UNNECESSARY).toBigInteger();
}
},
BIG_DECIMAL_IDENTIFIER_EXTRACTOR {
@Override
Serializable extractIdentifier(ResultSet resultSet) throws SQLException {
BigDecimal bigDecimal = resultSet.getBigDecimal(1);
if (resultSet.wasNull()) {
throw new IdentifierGenerationException("sequence returned null");
}
return bigDecimal;
}
};
abstract Serializable extractIdentifier(ResultSet resultSet) throws SQLException;
static IdentifierExtractor getIdentifierExtractor(Class integralType) {
if ((integralType == Integer.class) || (integralType == int.class)) {
return INTEGER_IDENTIFIER_EXTRACTOR;
}
if ((integralType == Long.class) || (integralType == long.class)) {
return LONG_IDENTIFIER_EXTRACTOR;
}
if (integralType == BigInteger.class) {
return BIG_INTEGER_IDENTIFIER_EXTRACTOR;
}
if (integralType == BigDecimal.class) {
return BIG_DECIMAL_IDENTIFIER_EXTRACTOR;
}
throw new IdentifierGenerationException("unsupported integral type: " + integralType);
}
}
@Override
public String toString() {
// for debugging only
return this.getClass().getSimpleName() + '(' + this.getSequenceName() + ')';
}
}