Oracle8iDialect.java

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.dialect;

import java.sql.CallableStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.List;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.hibernate.JDBCException;
import org.hibernate.QueryTimeoutException;
import org.hibernate.annotations.common.util.StringHelper;
import org.hibernate.cfg.Environment;
import org.hibernate.dialect.function.NoArgSQLFunction;
import org.hibernate.dialect.function.NvlFunction;
import org.hibernate.dialect.function.SQLFunctionTemplate;
import org.hibernate.dialect.function.StandardSQLFunction;
import org.hibernate.dialect.function.VarArgsSQLFunction;
import org.hibernate.dialect.pagination.AbstractLimitHandler;
import org.hibernate.dialect.pagination.LimitHandler;
import org.hibernate.dialect.pagination.LimitHelper;
import org.hibernate.engine.spi.QueryParameters;
import org.hibernate.engine.spi.RowSelection;
import org.hibernate.exception.ConstraintViolationException;
import org.hibernate.exception.LockAcquisitionException;
import org.hibernate.exception.LockTimeoutException;
import org.hibernate.exception.spi.SQLExceptionConversionDelegate;
import org.hibernate.exception.spi.TemplatedViolatedConstraintNameExtracter;
import org.hibernate.exception.spi.ViolatedConstraintNameExtracter;
import org.hibernate.hql.spi.id.IdTableSupportStandardImpl;
import org.hibernate.hql.spi.id.MultiTableBulkIdStrategy;
import org.hibernate.hql.spi.id.global.GlobalTemporaryTableBulkIdStrategy;
import org.hibernate.hql.spi.id.local.AfterUseAction;
import org.hibernate.internal.util.JdbcExceptionHelper;
import org.hibernate.procedure.internal.StandardCallableStatementSupport;
import org.hibernate.procedure.spi.CallableStatementSupport;
import org.hibernate.sql.CaseFragment;
import org.hibernate.sql.DecodeCaseFragment;
import org.hibernate.sql.JoinFragment;
import org.hibernate.sql.OracleJoinFragment;
import org.hibernate.type.StandardBasicTypes;
import org.hibernate.type.descriptor.sql.BitTypeDescriptor;
import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;

/**
 * A dialect for Oracle 8i.
 *
 * @author Steve Ebersole
 */
@SuppressWarnings("deprecation")
public class Oracle8iDialect extends Dialect {

	private static final Pattern DISTINCT_KEYWORD_PATTERN = Pattern.compile( "\\bdistinct\\b" );

	private static final Pattern GROUP_BY_KEYWORD_PATTERN = Pattern.compile( "\\bgroup\\sby\\b" );

	private static final Pattern ORDER_BY_KEYWORD_PATTERN = Pattern.compile( "\\border\\sby\\b" );

	private static final Pattern UNION_KEYWORD_PATTERN = Pattern.compile( "\\bunion\\b" );

	private static final Pattern SQL_STATEMENT_TYPE_PATTERN = Pattern.compile("^(?:\\/\\*.*?\\*\\/)?\\s*(select|insert|update|delete)\\s+.*?");

	private static final AbstractLimitHandler LIMIT_HANDLER = new AbstractLimitHandler() {
		@Override
		public String processSql(String sql, RowSelection selection) {
			final boolean hasOffset = LimitHelper.hasFirstRow( selection );
			sql = sql.trim();
			boolean isForUpdate = false;
			if (sql.toLowerCase(Locale.ROOT).endsWith( " for update" )) {
				sql = sql.substring( 0, sql.length() - 11 );
				isForUpdate = true;
			}

			final StringBuilder pagingSelect = new StringBuilder( sql.length() + 100 );
			if (hasOffset) {
				pagingSelect.append( "select * from ( select row_.*, rownum rownum_ from ( " );
			}
			else {
				pagingSelect.append( "select * from ( " );
			}
			pagingSelect.append( sql );
			if (hasOffset) {
				pagingSelect.append( " ) row_ ) where rownum_ <= ? and rownum_ > ?" );
			}
			else {
				pagingSelect.append( " ) where rownum <= ?" );
			}

			if (isForUpdate) {
				pagingSelect.append( " for update" );
			}

			return pagingSelect.toString();
		}

		@Override
		public boolean supportsLimit() {
			return true;
		}

		@Override
		public boolean bindLimitParametersInReverseOrder() {
			return true;
		}

		@Override
		public boolean useMaxForLimit() {
			return true;
		}
	};

	private static final int PARAM_LIST_SIZE_LIMIT = 1000;

	/**
	 * Constructs a Oracle8iDialect
	 */
	public Oracle8iDialect() {
		super();
		registerCharacterTypeMappings();
		registerNumericTypeMappings();
		registerDateTimeTypeMappings();
		registerLargeObjectTypeMappings();
		registerReverseHibernateTypeMappings();
		registerFunctions();
		registerDefaultProperties();
	}

	protected void registerCharacterTypeMappings() {
		registerColumnType( Types.CHAR, "char(1)" );
		registerColumnType( Types.VARCHAR, 4000, "varchar2($l)" );
		registerColumnType( Types.VARCHAR, "long" );
	}

	protected void registerNumericTypeMappings() {
		registerColumnType( Types.BIT, "number(1,0)" );
		registerColumnType( Types.BIGINT, "number(19,0)" );
		registerColumnType( Types.SMALLINT, "number(5,0)" );
		registerColumnType( Types.TINYINT, "number(3,0)" );
		registerColumnType( Types.INTEGER, "number(10,0)" );

		registerColumnType( Types.FLOAT, "float" );
		registerColumnType( Types.DOUBLE, "double precision" );
		registerColumnType( Types.NUMERIC, "number($p,$s)" );
		registerColumnType( Types.DECIMAL, "number($p,$s)" );

		registerColumnType( Types.BOOLEAN, "number(1,0)" );
	}

	protected void registerDateTimeTypeMappings() {
		registerColumnType( Types.DATE, "date" );
		registerColumnType( Types.TIME, "date" );
		registerColumnType( Types.TIMESTAMP, "date" );
	}

	protected void registerLargeObjectTypeMappings() {
		registerColumnType( Types.BINARY, 2000, "raw($l)" );
		registerColumnType( Types.BINARY, "long raw" );

		registerColumnType( Types.VARBINARY, 2000, "raw($l)" );
		registerColumnType( Types.VARBINARY, "long raw" );

		registerColumnType( Types.BLOB, "blob" );
		registerColumnType( Types.CLOB, "clob" );

		registerColumnType( Types.LONGVARCHAR, "long" );
		registerColumnType( Types.LONGVARBINARY, "long raw" );
	}

	protected void registerReverseHibernateTypeMappings() {
	}

	protected void registerFunctions() {
		registerFunction( "abs", new StandardSQLFunction("abs") );
		registerFunction( "sign", new StandardSQLFunction("sign", StandardBasicTypes.INTEGER) );

		registerFunction( "acos", new StandardSQLFunction("acos", StandardBasicTypes.DOUBLE) );
		registerFunction( "asin", new StandardSQLFunction("asin", StandardBasicTypes.DOUBLE) );
		registerFunction( "atan", new StandardSQLFunction("atan", StandardBasicTypes.DOUBLE) );
		registerFunction( "bitand", new StandardSQLFunction("bitand") );
		registerFunction( "cos", new StandardSQLFunction("cos", StandardBasicTypes.DOUBLE) );
		registerFunction( "cosh", new StandardSQLFunction("cosh", StandardBasicTypes.DOUBLE) );
		registerFunction( "exp", new StandardSQLFunction("exp", StandardBasicTypes.DOUBLE) );
		registerFunction( "ln", new StandardSQLFunction("ln", StandardBasicTypes.DOUBLE) );
		registerFunction( "sin", new StandardSQLFunction("sin", StandardBasicTypes.DOUBLE) );
		registerFunction( "sinh", new StandardSQLFunction("sinh", StandardBasicTypes.DOUBLE) );
		registerFunction( "stddev", new StandardSQLFunction("stddev", StandardBasicTypes.DOUBLE) );
		registerFunction( "sqrt", new StandardSQLFunction("sqrt", StandardBasicTypes.DOUBLE) );
		registerFunction( "tan", new StandardSQLFunction("tan", StandardBasicTypes.DOUBLE) );
		registerFunction( "tanh", new StandardSQLFunction("tanh", StandardBasicTypes.DOUBLE) );
		registerFunction( "variance", new StandardSQLFunction("variance", StandardBasicTypes.DOUBLE) );

		registerFunction( "round", new StandardSQLFunction("round") );
		registerFunction( "trunc", new StandardSQLFunction("trunc") );
		registerFunction( "ceil", new StandardSQLFunction("ceil") );
		registerFunction( "floor", new StandardSQLFunction("floor") );

		registerFunction( "chr", new StandardSQLFunction("chr", StandardBasicTypes.CHARACTER) );
		registerFunction( "initcap", new StandardSQLFunction("initcap") );
		registerFunction( "lower", new StandardSQLFunction("lower") );
		registerFunction( "ltrim", new StandardSQLFunction("ltrim") );
		registerFunction( "rtrim", new StandardSQLFunction("rtrim") );
		registerFunction( "soundex", new StandardSQLFunction("soundex") );
		registerFunction( "upper", new StandardSQLFunction("upper") );
		registerFunction( "ascii", new StandardSQLFunction("ascii", StandardBasicTypes.INTEGER) );

		registerFunction( "to_char", new StandardSQLFunction("to_char", StandardBasicTypes.STRING) );
		registerFunction( "to_date", new StandardSQLFunction("to_date", StandardBasicTypes.TIMESTAMP) );

		registerFunction( "current_date", new NoArgSQLFunction("current_date", StandardBasicTypes.DATE, false) );
		registerFunction( "current_time", new NoArgSQLFunction("current_timestamp", StandardBasicTypes.TIME, false) );
		registerFunction( "current_timestamp", new NoArgSQLFunction("current_timestamp", StandardBasicTypes.TIMESTAMP, false) );

		registerFunction( "last_day", new StandardSQLFunction("last_day", StandardBasicTypes.DATE) );
		registerFunction( "sysdate", new NoArgSQLFunction("sysdate", StandardBasicTypes.DATE, false) );
		registerFunction( "systimestamp", new NoArgSQLFunction("systimestamp", StandardBasicTypes.TIMESTAMP, false) );
		registerFunction( "uid", new NoArgSQLFunction("uid", StandardBasicTypes.INTEGER, false) );
		registerFunction( "user", new NoArgSQLFunction("user", StandardBasicTypes.STRING, false) );

		registerFunction( "rowid", new NoArgSQLFunction("rowid", StandardBasicTypes.LONG, false) );
		registerFunction( "rownum", new NoArgSQLFunction("rownum", StandardBasicTypes.LONG, false) );

		// Multi-param string dialect functions...
		registerFunction( "concat", new VarArgsSQLFunction(StandardBasicTypes.STRING, "", "||", "") );
		registerFunction( "instr", new StandardSQLFunction("instr", StandardBasicTypes.INTEGER) );
		registerFunction( "instrb", new StandardSQLFunction("instrb", StandardBasicTypes.INTEGER) );
		registerFunction( "lpad", new StandardSQLFunction("lpad", StandardBasicTypes.STRING) );
		registerFunction( "replace", new StandardSQLFunction("replace", StandardBasicTypes.STRING) );
		registerFunction( "rpad", new StandardSQLFunction("rpad", StandardBasicTypes.STRING) );
		registerFunction( "substr", new StandardSQLFunction("substr", StandardBasicTypes.STRING) );
		registerFunction( "substrb", new StandardSQLFunction("substrb", StandardBasicTypes.STRING) );
		registerFunction( "translate", new StandardSQLFunction("translate", StandardBasicTypes.STRING) );

		registerFunction( "substring", new StandardSQLFunction( "substr", StandardBasicTypes.STRING ) );
		registerFunction( "locate", new SQLFunctionTemplate( StandardBasicTypes.INTEGER, "instr(?2,?1)" ) );
		registerFunction( "bit_length", new SQLFunctionTemplate( StandardBasicTypes.INTEGER, "vsize(?1)*8" ) );
		registerFunction( "coalesce", new NvlFunction() );

		// Multi-param numeric dialect functions...
		registerFunction( "atan2", new StandardSQLFunction("atan2", StandardBasicTypes.FLOAT) );
		registerFunction( "log", new StandardSQLFunction("log", StandardBasicTypes.INTEGER) );
		registerFunction( "mod", new StandardSQLFunction("mod", StandardBasicTypes.INTEGER) );
		registerFunction( "nvl", new StandardSQLFunction("nvl") );
		registerFunction( "nvl2", new StandardSQLFunction("nvl2") );
		registerFunction( "power", new StandardSQLFunction("power", StandardBasicTypes.FLOAT) );

		// Multi-param date dialect functions...
		registerFunction( "add_months", new StandardSQLFunction("add_months", StandardBasicTypes.DATE) );
		registerFunction( "months_between", new StandardSQLFunction("months_between", StandardBasicTypes.FLOAT) );
		registerFunction( "next_day", new StandardSQLFunction("next_day", StandardBasicTypes.DATE) );

		registerFunction( "str", new StandardSQLFunction("to_char", StandardBasicTypes.STRING) );
	}

	protected void registerDefaultProperties() {
		getDefaultProperties().setProperty( Environment.USE_STREAMS_FOR_BINARY, "true" );
		getDefaultProperties().setProperty( Environment.STATEMENT_BATCH_SIZE, DEFAULT_BATCH_SIZE );
		// Oracle driver reports to support getGeneratedKeys(), but they only
		// support the version taking an array of the names of the columns to
		// be returned (via its RETURNING clause).  No other driver seems to
		// support this overloaded version.
		getDefaultProperties().setProperty( Environment.USE_GET_GENERATED_KEYS, "false" );
		getDefaultProperties().setProperty( Environment.BATCH_VERSIONED_DATA, "false" );
	}

	@Override
	protected SqlTypeDescriptor getSqlTypeDescriptorOverride(int sqlCode) {
		return sqlCode == Types.BOOLEAN ? BitTypeDescriptor.INSTANCE : super.getSqlTypeDescriptorOverride( sqlCode );
	}


	// features which change between 8i, 9i, and 10g ~~~~~~~~~~~~~~~~~~~~~~~~~~

	@Override
	public JoinFragment createOuterJoinFragment() {
		return new OracleJoinFragment();
	}

	@Override
	public String getCrossJoinSeparator() {
		return ", ";
	}

	/**
	 * Map case support to the Oracle DECODE function.  Oracle did not
	 * add support for CASE until 9i.
	 * <p/>
	 * {@inheritDoc}
	 */
	@Override
	public CaseFragment createCaseFragment() {
		return new DecodeCaseFragment();
	}

	@Override
	public LimitHandler getLimitHandler() {
		return LIMIT_HANDLER;
	}

	@Override
	public String getLimitString(String sql, boolean hasOffset) {
		sql = sql.trim();
		boolean isForUpdate = false;
		if ( sql.toLowerCase(Locale.ROOT).endsWith( " for update" ) ) {
			sql = sql.substring( 0, sql.length()-11 );
			isForUpdate = true;
		}

		final StringBuilder pagingSelect = new StringBuilder( sql.length()+100 );
		if (hasOffset) {
			pagingSelect.append( "select * from ( select row_.*, rownum rownum_ from ( " );
		}
		else {
			pagingSelect.append( "select * from ( " );
		}
		pagingSelect.append( sql );
		if (hasOffset) {
			pagingSelect.append( " ) row_ ) where rownum_ <= ? and rownum_ > ?" );
		}
		else {
			pagingSelect.append( " ) where rownum <= ?" );
		}

		if ( isForUpdate ) {
			pagingSelect.append( " for update" );
		}

		return pagingSelect.toString();
	}

	/**
	 * Allows access to the basic {@link Dialect#getSelectClauseNullString}
	 * implementation...
	 *
	 * @param sqlType The {@link java.sql.Types} mapping type code
	 * @return The appropriate select cluse fragment
	 */
	public String getBasicSelectClauseNullString(int sqlType) {
		return super.getSelectClauseNullString( sqlType );
	}

	@Override
	public String getSelectClauseNullString(int sqlType) {
		switch(sqlType) {
			case Types.VARCHAR:
			case Types.CHAR:
				return "to_char(null)";
			case Types.DATE:
			case Types.TIMESTAMP:
			case Types.TIME:
				return "to_date(null)";
			default:
				return "to_number(null)";
		}
	}

	@Override
	public String getCurrentTimestampSelectString() {
		return "select sysdate from dual";
	}

	@Override
	public String getCurrentTimestampSQLFunctionName() {
		return "sysdate";
	}


	// features which remain constant across 8i, 9i, and 10g ~~~~~~~~~~~~~~~~~~

	@Override
	public String getAddColumnString() {
		return "add";
	}

	@Override
	public String getSequenceNextValString(String sequenceName) {
		return "select " + getSelectSequenceNextValString( sequenceName ) + " from dual";
	}

	@Override
	public String getSelectSequenceNextValString(String sequenceName) {
		return sequenceName + ".nextval";
	}

	@Override
	public String getCreateSequenceString(String sequenceName) {
		//starts with 1, implicitly
		return "create sequence " + sequenceName;
	}

	@Override
	protected String getCreateSequenceString(String sequenceName, int initialValue, int incrementSize) {
		if ( initialValue < 0 && incrementSize > 0 ) {
			return
				String.format(
						"%s minvalue %d start with %d increment by %d",
						getCreateSequenceString( sequenceName ),
						initialValue,
						initialValue,
						incrementSize
				);
		}
		else if ( initialValue > 0 && incrementSize < 0 ) {
			return
				String.format(
						"%s maxvalue %d start with %d increment by %d",
						getCreateSequenceString( sequenceName ),
						initialValue,
						initialValue,
						incrementSize
				);
		}
		else {
			return
				String.format(
						"%s start with %d increment by  %d",
						getCreateSequenceString( sequenceName ),
						initialValue,
						incrementSize
				);
		}
	}

	@Override
	public String getDropSequenceString(String sequenceName) {
		return "drop sequence " + sequenceName;
	}

	@Override
	public String getCascadeConstraintsString() {
		return " cascade constraints";
	}

	@Override
	public boolean dropConstraints() {
		return false;
	}

	@Override
	public String getForUpdateNowaitString() {
		return " for update nowait";
	}

	@Override
	public boolean supportsSequences() {
		return true;
	}

	@Override
	public boolean supportsPooledSequences() {
		return true;
	}

	@Override
	public boolean supportsLimit() {
		return true;
	}

	@Override
	public String getForUpdateString(String aliases) {
		return getForUpdateString() + " of " + aliases;
	}

	@Override
	public String getForUpdateNowaitString(String aliases) {
		return getForUpdateString() + " of " + aliases + " nowait";
	}

	@Override
	public boolean bindLimitParametersInReverseOrder() {
		return true;
	}

	@Override
	public boolean useMaxForLimit() {
		return true;
	}

	@Override
	public boolean forUpdateOfColumns() {
		return true;
	}

	@Override
	public String getQuerySequencesString() {
		return    " select sequence_name from all_sequences"
				+ "  union"
				+ " select synonym_name"
				+ "   from all_synonyms us, all_sequences asq"
				+ "  where asq.sequence_name = us.table_name"
				+ "    and asq.sequence_owner = us.table_owner";
	}

	@Override
	public String getSelectGUIDString() {
		return "select rawtohex(sys_guid()) from dual";
	}

	@Override
	public ViolatedConstraintNameExtracter getViolatedConstraintNameExtracter() {
		return EXTRACTER;
	}

	private static final ViolatedConstraintNameExtracter EXTRACTER = new TemplatedViolatedConstraintNameExtracter() {

		/**
		 * Extract the name of the violated constraint from the given SQLException.
		 *
		 * @param sqle The exception that was the result of the constraint violation.
		 * @return The extracted constraint name.
		 */
		@Override
		protected String doExtractConstraintName(SQLException sqle) throws NumberFormatException {
			final int errorCode = JdbcExceptionHelper.extractErrorCode( sqle );
			if ( errorCode == 1 || errorCode == 2291 || errorCode == 2292 ) {
				return extractUsingTemplate( "(", ")", sqle.getMessage() );
			}
			else if ( errorCode == 1400 ) {
				// simple nullability constraint
				return null;
			}
			else {
				return null;
			}
		}

	};

	@Override
	public SQLExceptionConversionDelegate buildSQLExceptionConversionDelegate() {
		return new SQLExceptionConversionDelegate() {
			@Override
			public JDBCException convert(SQLException sqlException, String message, String sql) {
				// interpreting Oracle exceptions is much much more precise based on their specific vendor codes.

				final int errorCode = JdbcExceptionHelper.extractErrorCode( sqlException );


				// lock timeouts ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

				if ( errorCode == 30006 ) {
					// ORA-30006: resource busy; acquire with WAIT timeout expired
					throw new LockTimeoutException( message, sqlException, sql );
				}
				else if ( errorCode == 54 ) {
					// ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
					throw new LockTimeoutException( message, sqlException, sql );
				}
				else if ( 4021 == errorCode ) {
					// ORA-04021 timeout occurred while waiting to lock object
					throw new LockTimeoutException( message, sqlException, sql );
				}


				// deadlocks ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

				if ( 60 == errorCode ) {
					// ORA-00060: deadlock detected while waiting for resource
					return new LockAcquisitionException( message, sqlException, sql );
				}
				else if ( 4020 == errorCode ) {
					// ORA-04020 deadlock detected while trying to lock object
					return new LockAcquisitionException( message, sqlException, sql );
				}


				// query cancelled ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

				if ( 1013 == errorCode ) {
					// ORA-01013: user requested cancel of current operation
					throw new QueryTimeoutException(  message, sqlException, sql );
				}


				// data integrity violation ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

				if ( 1407 == errorCode ) {
					// ORA-01407: cannot update column to NULL
					final String constraintName = getViolatedConstraintNameExtracter().extractConstraintName( sqlException );
					return new ConstraintViolationException( message, sqlException, sql, constraintName );
				}

				return null;
			}
		};
	}

	@Override
	public int registerResultSetOutParameter(CallableStatement statement, int col) throws SQLException {
		//	register the type of the out param - an Oracle specific type
		statement.registerOutParameter( col, OracleTypesHelper.INSTANCE.getOracleCursorTypeSqlType() );
		col++;
		return col;
	}

	@Override
	public ResultSet getResultSet(CallableStatement ps) throws SQLException {
		ps.execute();
		return (ResultSet) ps.getObject( 1 );
	}

	@Override
	public boolean supportsUnionAll() {
		return true;
	}

	@Override
	public boolean supportsCommentOn() {
		return true;
	}

	@Override
	public MultiTableBulkIdStrategy getDefaultMultiTableBulkIdStrategy() {
		return new GlobalTemporaryTableBulkIdStrategy(
				new IdTableSupportStandardImpl() {
					@Override
					public String generateIdTableName(String baseName) {
						final String name = super.generateIdTableName( baseName );
						return name.length() > 30 ? name.substring( 0, 30 ) : name;
					}

					@Override
					public String getCreateIdTableCommand() {
						return "create global temporary table";
					}

					@Override
					public String getCreateIdTableStatementOptions() {
						return "on commit delete rows";
					}
				},
				AfterUseAction.CLEAN
		);
	}

	@Override
	public boolean supportsCurrentTimestampSelection() {
		return true;
	}

	@Override
	public boolean isCurrentTimestampSelectStringCallable() {
		return false;
	}

	@Override
	public boolean supportsEmptyInList() {
		return false;
	}
	
	@Override
	public boolean supportsExistsInSelect() {
		return false;
	}

	@Override
	public int getInExpressionCountLimit() {
		return PARAM_LIST_SIZE_LIMIT;
	}
	
	@Override
	public boolean forceLobAsLastValue() {
		return true;
	}

	/**
	 * For Oracle, the FOR UPDATE clause cannot be applied when using ORDER BY, DISTINCT or views.
	 * @param parameters
	 * @return
	 @see <a href="https://docs.oracle.com/database/121/SQLRF/statements_10002.htm#SQLRF01702">Oracle FOR UPDATE restrictions</a>
	 */
	@Override
	public boolean useFollowOnLocking(QueryParameters parameters) {

		if (parameters != null ) {
			String lowerCaseSQL = parameters.getFilteredSQL().toLowerCase();

			return
				DISTINCT_KEYWORD_PATTERN.matcher( lowerCaseSQL ).find() ||
				GROUP_BY_KEYWORD_PATTERN.matcher( lowerCaseSQL ).find() ||
				UNION_KEYWORD_PATTERN.matcher( lowerCaseSQL ).find() ||
				(
					parameters.hasRowSelection() &&
						(
							ORDER_BY_KEYWORD_PATTERN.matcher( lowerCaseSQL ).find() ||
							parameters.getRowSelection().getFirstRow() != null
						)
				);
		}
		else {
			return true;
		}
	}
	
	@Override
	public String getNotExpression( String expression ) {
		return "not (" + expression + ")";
	}
	
	@Override
	public String getQueryHintString(String sql, String hints) {
		String statementType = statementType(sql);

		final int pos = sql.indexOf( statementType );
		if ( pos > -1 ) {
			final StringBuilder buffer = new StringBuilder( sql.length() + hints.length() + 8 );
			if ( pos > 0 ) {
				buffer.append( sql.substring( 0, pos ) );
			}
			buffer
			.append( statementType )
			.append( " /*+ " )
			.append( hints )
			.append( " */" )
			.append( sql.substring( pos + statementType.length() ) );
			sql = buffer.toString();
		}

		return sql;
	}
	
	@Override
	public int getMaxAliasLength() {
		// Oracle's max identifier length is 30, but Hibernate needs to add "uniqueing info" so we account for that,
		return 20;
	}

	@Override
	public CallableStatementSupport getCallableStatementSupport() {
		// Oracle supports returning cursors
		return StandardCallableStatementSupport.REF_CURSOR_INSTANCE;
	}

	@Override
	public boolean canCreateSchema() {
		return false;
	}

	@Override
	public String getCurrentSchemaCommand() {
		return "SELECT SYS_CONTEXT('USERENV', 'CURRENT_SCHEMA') FROM DUAL";
	}

	@Override
	public boolean supportsPartitionBy() {
		return true;
	}

	protected String statementType(String sql) {
		Matcher matcher = SQL_STATEMENT_TYPE_PATTERN.matcher( sql );

		if(matcher.matches() && matcher.groupCount() == 1) {
			return matcher.group(1);
		}

		throw new IllegalArgumentException( "Can't determine SQL statement type for statement: " + sql );
	}
}