//$Id: Dialect.java 11658 2007-06-08 01:48:54Z steve.ebersole@jboss.com $
package org.hibernate.dialect;
import java.sql.CallableStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.MappingException;
import org.hibernate.QueryException;
import org.hibernate.cfg.Environment;
import org.hibernate.dialect.function.CastFunction;
import org.hibernate.dialect.function.SQLFunction;
import org.hibernate.dialect.function.SQLFunctionTemplate;
import org.hibernate.dialect.function.StandardSQLFunction;
import org.hibernate.dialect.lock.LockingStrategy;
import org.hibernate.dialect.lock.SelectLockingStrategy;
import org.hibernate.engine.Mapping;
import org.hibernate.exception.SQLExceptionConverter;
import org.hibernate.exception.SQLStateConverter;
import org.hibernate.exception.ViolatedConstraintNameExtracter;
import org.hibernate.id.IdentityGenerator;
import org.hibernate.id.SequenceGenerator;
import org.hibernate.id.TableHiLoGenerator;
import org.hibernate.mapping.Column;
import org.hibernate.persister.entity.Lockable;
import org.hibernate.sql.ANSICaseFragment;
import org.hibernate.sql.ANSIJoinFragment;
import org.hibernate.sql.CaseFragment;
import org.hibernate.sql.JoinFragment;
import org.hibernate.sql.ForUpdateFragment;
import org.hibernate.type.Type;
import org.hibernate.util.ReflectHelper;
import org.hibernate.util.StringHelper;
/**
* Represents a dialect of SQL implemented by a particular RDBMS.
* Subclasses implement Hibernate compatibility with different systems.<br>
* <br>
* Subclasses should provide a public default constructor that <tt>register()</tt>
* a set of type mappings and default Hibernate properties.<br>
* <br>
* Subclasses should be immutable.
*
* @author Gavin King, David Channon
*/
public abstract class Dialect {
private static final Log log = LogFactory.getLog( Dialect.class );
public static final String DEFAULT_BATCH_SIZE = "15";
public static final String NO_BATCH = "0";
/**
* Characters used for quoting SQL identifiers
*/
public static final String QUOTE = "`\"[";
public static final String CLOSED_QUOTE = "`\"]";
// build the map of standard ANSI SQL aggregation functions ~~~~~~~~~~~~~~~
private static final Map STANDARD_AGGREGATE_FUNCTIONS = new HashMap();
static {
STANDARD_AGGREGATE_FUNCTIONS.put( "count", new StandardSQLFunction("count") {
public Type getReturnType(Type columnType, Mapping mapping) {
return Hibernate.LONG;
}
} );
STANDARD_AGGREGATE_FUNCTIONS.put( "avg", new StandardSQLFunction("avg") {
public Type getReturnType(Type columnType, Mapping mapping) throws QueryException {
int[] sqlTypes;
try {
sqlTypes = columnType.sqlTypes( mapping );
}
catch ( MappingException me ) {
throw new QueryException( me );
}
if ( sqlTypes.length != 1 ) throw new QueryException( "multi-column type in avg()" );
return Hibernate.DOUBLE;
}
} );
STANDARD_AGGREGATE_FUNCTIONS.put( "max", new StandardSQLFunction("max") );
STANDARD_AGGREGATE_FUNCTIONS.put( "min", new StandardSQLFunction("min") );
STANDARD_AGGREGATE_FUNCTIONS.put( "sum", new StandardSQLFunction("sum") {
public Type getReturnType(Type columnType, Mapping mapping) {
//pre H3.2 behavior: super.getReturnType(ct, m);
int[] sqlTypes;
try {
sqlTypes = columnType.sqlTypes( mapping );
}
catch ( MappingException me ) {
throw new QueryException( me );
}
if ( sqlTypes.length != 1 ) throw new QueryException( "multi-column type in sum()" );
int sqlType = sqlTypes[0];
// First allow the actual type to control the return value. (the actual underlying sqltype could actually be different)
if ( columnType == Hibernate.BIG_INTEGER ) {
return Hibernate.BIG_INTEGER;
}
else if ( columnType == Hibernate.BIG_DECIMAL ) {
return Hibernate.BIG_DECIMAL;
}
else if ( columnType == Hibernate.LONG || columnType == Hibernate.SHORT || columnType == Hibernate.INTEGER) {
return Hibernate.LONG;
}
else if ( columnType == Hibernate.FLOAT || columnType == Hibernate.DOUBLE) {
return Hibernate.DOUBLE;
}
// finally use the sqltype if == on Hibernate types did not find a match.
if ( sqlType == Types.NUMERIC ) {
return columnType; //because numeric can be anything
}
else if ( sqlType == Types.FLOAT || sqlType == Types.DOUBLE || sqlType == Types.DECIMAL || sqlType == Types.REAL) {
return Hibernate.DOUBLE;
}
else if ( sqlType == Types.BIGINT || sqlType == Types.INTEGER || sqlType == Types.SMALLINT || sqlType == Types.TINYINT ) {
return Hibernate.LONG;
}
else {
return columnType;
}
}
});
}
private final TypeNames typeNames = new TypeNames();
private final TypeNames hibernateTypeNames = new TypeNames();
private final Properties properties = new Properties();
private final Map sqlFunctions = new HashMap();
private final Set sqlKeywords = new HashSet();
// constructors and factory methods ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
protected Dialect() {
log.info( "Using dialect: " + this );
sqlFunctions.putAll( STANDARD_AGGREGATE_FUNCTIONS );
// standard sql92 functions (can be overridden by subclasses)
registerFunction( "substring", new SQLFunctionTemplate( Hibernate.STRING, "substring(?1, ?2, ?3)" ) );
registerFunction( "locate", new SQLFunctionTemplate( Hibernate.INTEGER, "locate(?1, ?2, ?3)" ) );
registerFunction( "trim", new SQLFunctionTemplate( Hibernate.STRING, "trim(?1 ?2 ?3 ?4)" ) );
registerFunction( "length", new StandardSQLFunction( "length", Hibernate.INTEGER ) );
registerFunction( "bit_length", new StandardSQLFunction( "bit_length", Hibernate.INTEGER ) );
registerFunction( "coalesce", new StandardSQLFunction( "coalesce" ) );
registerFunction( "nullif", new StandardSQLFunction( "nullif" ) );
registerFunction( "abs", new StandardSQLFunction( "abs" ) );
registerFunction( "mod", new StandardSQLFunction( "mod", Hibernate.INTEGER) );
registerFunction( "sqrt", new StandardSQLFunction( "sqrt", Hibernate.DOUBLE) );
registerFunction( "upper", new StandardSQLFunction("upper") );
registerFunction( "lower", new StandardSQLFunction("lower") );
registerFunction( "cast", new CastFunction() );
registerFunction( "extract", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(?1 ?2 ?3)") );
//map second/minute/hour/day/month/year to ANSI extract(), override on subclasses
registerFunction( "second", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(second from ?1)") );
registerFunction( "minute", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(minute from ?1)") );
registerFunction( "hour", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(hour from ?1)") );
registerFunction( "day", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(day from ?1)") );
registerFunction( "month", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(month from ?1)") );
registerFunction( "year", new SQLFunctionTemplate(Hibernate.INTEGER, "extract(year from ?1)") );
registerFunction( "str", new SQLFunctionTemplate(Hibernate.STRING, "cast(?1 as char)") );
// register hibernate types for default use in scalar sqlquery type auto detection
registerHibernateType( Types.BIGINT, Hibernate.BIG_INTEGER.getName() );
registerHibernateType( Types.BINARY, Hibernate.BINARY.getName() );
registerHibernateType( Types.BIT, Hibernate.BOOLEAN.getName() );
registerHibernateType( Types.CHAR, Hibernate.CHARACTER.getName() );
registerHibernateType( Types.DATE, Hibernate.DATE.getName() );
registerHibernateType( Types.DOUBLE, Hibernate.DOUBLE.getName() );
registerHibernateType( Types.FLOAT, Hibernate.FLOAT.getName() );
registerHibernateType( Types.INTEGER, Hibernate.INTEGER.getName() );
registerHibernateType( Types.SMALLINT, Hibernate.SHORT.getName() );
registerHibernateType( Types.TINYINT, Hibernate.BYTE.getName() );
registerHibernateType( Types.TIME, Hibernate.TIME.getName() );
registerHibernateType( Types.TIMESTAMP, Hibernate.TIMESTAMP.getName() );
registerHibernateType( Types.VARCHAR, Hibernate.STRING.getName() );
registerHibernateType( Types.VARBINARY, Hibernate.BINARY.getName() );
registerHibernateType( Types.NUMERIC, Hibernate.BIG_DECIMAL.getName() );
registerHibernateType( Types.DECIMAL, Hibernate.BIG_DECIMAL.getName() );
registerHibernateType( Types.BLOB, Hibernate.BLOB.getName() );
registerHibernateType( Types.CLOB, Hibernate.CLOB.getName() );
registerHibernateType( Types.REAL, Hibernate.FLOAT.getName() );
}
/**
* Get an instance of the dialect specified by the current <tt>System</tt> properties.
*
* @return The specified Dialect
* @throws HibernateException If no dialect was specified, or if it could not be instantiated.
*/
public static Dialect getDialect() throws HibernateException {
String dialectName = Environment.getProperties().getProperty( Environment.DIALECT );
return instantiateDialect( dialectName );
}
/**
* Get an instance of the dialect specified by the given properties or by
* the current <tt>System</tt> properties.
*
* @param props The properties to use for finding the dialect class to use.
* @return The specified Dialect
* @throws HibernateException If no dialect was specified, or if it could not be instantiated.
*/
public static Dialect getDialect(Properties props) throws HibernateException {
String dialectName = props.getProperty( Environment.DIALECT );
if ( dialectName == null ) {
return getDialect();
}
return instantiateDialect( dialectName );
}
private static Dialect instantiateDialect(String dialectName) throws HibernateException {
if ( dialectName == null ) {
throw new HibernateException( "The dialect was not set. Set the property hibernate.dialect." );
}
try {
return ( Dialect ) ReflectHelper.classForName( dialectName ).newInstance();
}
catch ( ClassNotFoundException cnfe ) {
throw new HibernateException( "Dialect class not found: " + dialectName );
}
catch ( Exception e ) {
throw new HibernateException( "Could not instantiate dialect class", e );
}
}
/**
* Retrieve a set of default Hibernate properties for this database.
*
* @return a set of Hibernate properties
*/
public final Properties getDefaultProperties() {
return properties;
}
public String toString() {
return getClass().getName();
}
// database type mapping support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Get the name of the database type associated with the given
* {@link java.sql.Types} typecode.
*
* @param code The {@link java.sql.Types} typecode
* @return the database type name
* @throws HibernateException If no mapping was specified for that type.
*/
public String getTypeName(int code) throws HibernateException {
String result = typeNames.get( code );
if ( result == null ) {
throw new HibernateException( "No default type mapping for (java.sql.Types) " + code );
}
return result;
}
/**
* Get the name of the database type associated with the given
* {@link java.sql.Types} typecode with the given storage specification
* parameters.
*
* @param code The {@link java.sql.Types} typecode
* @param length The datatype length
* @param precision The datatype precision
* @param scale The datatype scale
* @return the database type name
* @throws HibernateException If no mapping was specified for that type.
*/
public String getTypeName(int code, int length, int precision, int scale) throws HibernateException {
String result = typeNames.get( code, length, precision, scale );
if ( result == null ) {
throw new HibernateException(
"No type mapping for java.sql.Types code: " +
code +
", length: " +
length
);
}
return result;
}
/**
* Get the name of the database type appropriate for casting operations
* (via the CAST() SQL function) for the given {@link java.sql.Types} typecode.
*
* @param code The {@link java.sql.Types} typecode
* @return The database type name
*/
public String getCastTypeName(int code) {
return getTypeName( code, Column.DEFAULT_LENGTH, Column.DEFAULT_PRECISION, Column.DEFAULT_SCALE );
}
/**
* Subclasses register a type name for the given type code and maximum
* column length. <tt>$l</tt> in the type name with be replaced by the
* column length (if appropriate).
*
* @param code The {@link java.sql.Types} typecode
* @param capacity The maximum length of database type
* @param name The database type name
*/
protected void registerColumnType(int code, int capacity, String name) {
typeNames.put( code, capacity, name );
}
/**
* Subclasses register a type name for the given type code. <tt>$l</tt> in
* the type name with be replaced by the column length (if appropriate).
*
* @param code The {@link java.sql.Types} typecode
* @param name The database type name
*/
protected void registerColumnType(int code, String name) {
typeNames.put( code, name );
}
// hibernate type mapping support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Get the name of the Hibernate {@link org.hibernate.type.Type} associated with th given
* {@link java.sql.Types} typecode.
*
* @param code The {@link java.sql.Types} typecode
* @return The Hibernate {@link org.hibernate.type.Type} name.
* @throws HibernateException If no mapping was specified for that type.
*/
public String getHibernateTypeName(int code) throws HibernateException {
String result = hibernateTypeNames.get( code );
if ( result == null ) {
throw new HibernateException( "No Hibernate type mapping for java.sql.Types code: " + code );
}
return result;
}
/**
* Get the name of the Hibernate {@link org.hibernate.type.Type} associated
* with the given {@link java.sql.Types} typecode with the given storage
* specification parameters.
*
* @param code The {@link java.sql.Types} typecode
* @param length The datatype length
* @param precision The datatype precision
* @param scale The datatype scale
* @return The Hibernate {@link org.hibernate.type.Type} name.
* @throws HibernateException If no mapping was specified for that type.
*/
public String getHibernateTypeName(int code, int length, int precision, int scale) throws HibernateException {
String result = hibernateTypeNames.get( code, length, precision, scale );
if ( result == null ) {
throw new HibernateException(
"No Hibernate type mapping for java.sql.Types code: " +
code +
", length: " +
length
);
}
return result;
}
/**
* Registers a Hibernate {@link org.hibernate.type.Type} name for the given
* {@link java.sql.Types} type code and maximum column length.
*
* @param code The {@link java.sql.Types} typecode
* @param capacity The maximum length of database type
* @param name The Hibernate {@link org.hibernate.type.Type} name
*/
protected void registerHibernateType(int code, int capacity, String name) {
hibernateTypeNames.put( code, capacity, name);
}
/**
* Registers a Hibernate {@link org.hibernate.type.Type} name for the given
* {@link java.sql.Types} type code.
*
* @param code The {@link java.sql.Types} typecode
* @param name The Hibernate {@link org.hibernate.type.Type} name
*/
protected void registerHibernateType(int code, String name) {
hibernateTypeNames.put( code, name);
}
// function support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
protected void registerFunction(String name, SQLFunction function) {
sqlFunctions.put( name, function );
}
/**
* Retrieves a map of the dialect's registered fucntions
* (functionName => {@link org.hibernate.dialect.function.SQLFunction}).
*
* @return The map of registered functions.
*/
public final Map getFunctions() {
return sqlFunctions;
}
// keyword support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
protected void registerKeyword(String word) {
sqlKeywords.add(word);
}
public Set getKeywords() {
return sqlKeywords;
}
// native identifier generatiion ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* The class (which implements {@link org.hibernate.id.IdentifierGenerator})
* which acts as this dialects native generation strategy.
* <p/>
* Comes into play whenever the user specifies the native generator.
*
* @return The native generator class.
*/
public Class getNativeIdentifierGeneratorClass() {
if ( supportsIdentityColumns() ) {
return IdentityGenerator.class;
}
else if ( supportsSequences() ) {
return SequenceGenerator.class;
}
else {
return TableHiLoGenerator.class;
}
}
// IDENTITY support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support identity column key generation?
*
* @return True if IDENTITY columns are supported; false otherwise.
*/
public boolean supportsIdentityColumns() {
return false;
}
/**
* Does the dialect support some form of inserting and selecting
* the generated IDENTITY value all in the same statement.
*
* @return True if the dialect supports selecting the just
* generated IDENTITY in the insert statement.
*/
public boolean supportsInsertSelectIdentity() {
return false;
}
/**
* Whether this dialect have an Identity clause added to the data type or a
* completely seperate identity data type
*
* @return boolean
*/
public boolean hasDataTypeInIdentityColumn() {
return true;
}
/**
* Provided we {@link #supportsInsertSelectIdentity}, then attch the
* "select identity" clause to the insert statement.
* <p/>
* Note, if {@link #supportsInsertSelectIdentity} == false then
* the insert-string should be returned without modification.
*
* @param insertString The insert command
* @return The insert command with any necessary identity select
* clause attached.
*/
public String appendIdentitySelectToInsert(String insertString) {
return insertString;
}
/**
* Get the select command to use to retrieve the last generated IDENTITY
* value for a particuar table
*
* @param table The table into which the insert was done
* @param column The PK column.
* @param type The {@link java.sql.Types} type code.
* @return The appropriate select command
* @throws MappingException If IDENTITY generation is not supported.
*/
public String getIdentitySelectString(String table, String column, int type) throws MappingException {
return getIdentitySelectString();
}
/**
* Get the select command to use to retrieve the last generated IDENTITY
* value.
*
* @return The appropriate select command
* @throws MappingException If IDENTITY generation is not supported.
*/
protected String getIdentitySelectString() throws MappingException {
throw new MappingException( "Dialect does not support identity key generation" );
}
/**
* The syntax used during DDL to define a column as being an IDENTITY of
* a particular type.
*
* @param type The {@link java.sql.Types} type code.
* @return The appropriate DDL fragment.
* @throws MappingException If IDENTITY generation is not supported.
*/
public String getIdentityColumnString(int type) throws MappingException {
return getIdentityColumnString();
}
/**
* The syntax used during DDL to define a column as being an IDENTITY.
*
* @return The appropriate DDL fragment.
* @throws MappingException If IDENTITY generation is not supported.
*/
protected String getIdentityColumnString() throws MappingException {
throw new MappingException( "Dialect does not support identity key generation" );
}
/**
* The keyword used to insert a generated value into an identity column (or null).
* Need if the dialect does not support inserts that specify no column values.
*
* @return The appropriate keyword.
*/
public String getIdentityInsertString() {
return null;
}
// SEQUENCE support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support sequences?
*
* @return True if sequences supported; false otherwise.
*/
public boolean supportsSequences() {
return false;
}
/**
* Does this dialect support "pooled" sequences. Not aware of a better
* name for this. Essentially can we specify the initial and increment values?
*
* @return True if such "pooled" sequences are supported; false otherwise.
* @see #getCreateSequenceStrings(String, int, int)
* @see #getCreateSequenceString(String, int, int)
*/
public boolean supportsPooledSequences() {
return false;
}
/**
* Generate the appropriate select statement to to retreive the next value
* of a sequence.
* <p/>
* This should be a "stand alone" select statement.
*
* @param sequenceName the name of the sequence
* @return String The "nextval" select string.
* @throws MappingException If sequences are not supported.
*/
public String getSequenceNextValString(String sequenceName) throws MappingException {
throw new MappingException( "Dialect does not support sequences" );
}
/**
* Generate the select expression fragment that will retreive the next
* value of a sequence as part of another (typically DML) statement.
* <p/>
* This differs from {@link #getSequenceNextValString(String)} in that this
* should return an expression usable within another statement.
*
* @param sequenceName the name of the sequence
* @return The "nextval" fragment.
* @throws MappingException If sequences are not supported.
*/
public String getSelectSequenceNextValString(String sequenceName) throws MappingException {
throw new MappingException( "Dialect does not support sequences" );
}
/**
* The multiline script used to create a sequence.
*
* @param sequenceName The name of the sequence
* @return The sequence creation commands
* @throws MappingException If sequences are not supported.
* @deprecated Use {@link #getCreateSequenceString(String, int, int)} instead
*/
public String[] getCreateSequenceStrings(String sequenceName) throws MappingException {
return new String[] { getCreateSequenceString( sequenceName ) };
}
/**
* An optional multi-line form for databases which {@link #supportsPooledSequences()}.
*
* @param sequenceName The name of the sequence
* @param initialValue The initial value to apply to 'create sequence' statement
* @param incrementSize The increment value to apply to 'create sequence' statement
* @return The sequence creation commands
* @throws MappingException If sequences are not supported.
*/
public String[] getCreateSequenceStrings(String sequenceName, int initialValue, int incrementSize) throws MappingException {
return new String[] { getCreateSequenceString( sequenceName, initialValue, incrementSize ) };
}
/**
* Typically dialects which support sequences can create a sequence
* with a single command. This is convenience form of
* {@link #getCreateSequenceStrings} to help facilitate that.
* <p/>
* Dialects which support sequences and can create a sequence in a
* single command need *only* override this method. Dialects
* which support sequences but require multiple commands to create
* a sequence should instead override {@link #getCreateSequenceStrings}.
*
* @param sequenceName The name of the sequence
* @return The sequence creation command
* @throws MappingException If sequences are not supported.
*/
protected String getCreateSequenceString(String sequenceName) throws MappingException {
throw new MappingException( "Dialect does not support sequences" );
}
/**
* Overloaded form of {@link #getCreateSequenceString(String)}, additionally
* taking the initial value and increment size to be applied to the sequence
* definition.
* </p>
* The default definition is to suffix {@link #getCreateSequenceString(String)}
* with the string: " start with {initialValue} increment by {incrementSize}" where
* {initialValue} and {incrementSize} are replacement placeholders. Generally
* dialects should only need to override this method if different key phrases
* are used to apply the allocation information.
*
* @param sequenceName The name of the sequence
* @param initialValue The initial value to apply to 'create sequence' statement
* @param incrementSize The increment value to apply to 'create sequence' statement
* @return The sequence creation command
* @throws MappingException If sequences are not supported.
*/
protected String getCreateSequenceString(String sequenceName, int initialValue, int incrementSize) throws MappingException {
if ( supportsPooledSequences() ) {
return getCreateSequenceString( sequenceName ) + " start with " + initialValue + " increment by " + incrementSize;
}
throw new MappingException( "Dialect does not support pooled sequences" );
}
/**
* The multiline script used to drop a sequence.
*
* @param sequenceName The name of the sequence
* @return The sequence drop commands
* @throws MappingException If sequences are not supported.
*/
public String[] getDropSequenceStrings(String sequenceName) throws MappingException {
return new String[]{getDropSequenceString( sequenceName )};
}
/**
* Typically dialects which support sequences can drop a sequence
* with a single command. This is convenience form of
* {@link #getDropSequenceStrings} to help facilitate that.
* <p/>
* Dialects which support sequences and can drop a sequence in a
* single command need *only* override this method. Dialects
* which support sequences but require multiple commands to drop
* a sequence should instead override {@link #getDropSequenceStrings}.
*
* @param sequenceName The name of the sequence
* @return The sequence drop commands
* @throws MappingException If sequences are not supported.
*/
protected String getDropSequenceString(String sequenceName) throws MappingException {
throw new MappingException( "Dialect does not support sequences" );
}
/**
* Get the select command used retrieve the names of all sequences.
*
* @return The select command; or null if sequences are not supported.
* @see org.hibernate.tool.hbm2ddl.SchemaUpdate
*/
public String getQuerySequencesString() {
return null;
}
// GUID support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Get the command used to select a GUID from the underlying database.
* <p/>
* Optional operation.
*
* @return The appropriate command.
*/
public String getSelectGUIDString() {
throw new UnsupportedOperationException( "dialect does not support GUIDs" );
}
// limit/offset support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support some form of limiting query results
* via a SQL clause?
*
* @return True if this dialect supports some form of LIMIT.
*/
public boolean supportsLimit() {
return false;
}
/**
* Does this dialect's LIMIT support (if any) additionally
* support specifying an offset?
*
* @return True if the dialect supports an offset within the limit support.
*/
public boolean supportsLimitOffset() {
return supportsLimit();
}
/**
* Does this dialect support bind variables (i.e., prepared statememnt
* parameters) for its limit/offset?
*
* @return True if bind variables can be used; false otherwise.
*/
public boolean supportsVariableLimit() {
return supportsLimit();
}
/**
* ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit.
* Does this dialect require us to bind the parameters in reverse order?
*
* @return true if the correct order is limit, offset
*/
public boolean bindLimitParametersInReverseOrder() {
return false;
}
/**
* Does the <tt>LIMIT</tt> clause come at the start of the
* <tt>SELECT</tt> statement, rather than at the end?
*
* @return true if limit parameters should come before other parameters
*/
public boolean bindLimitParametersFirst() {
return false;
}
/**
* Does the <tt>LIMIT</tt> clause take a "maximum" row number instead
* of a total number of returned rows?
* <p/>
* This is easiest understood via an example. Consider you have a table
* with 20 rows, but you only want to retrieve rows number 11 through 20.
* Generally, a limit with offset would say that the offset = 11 and the
* limit = 10 (we only want 10 rows at a time); this is specifying the
* total number of returned rows. Some dialects require that we instead
* specify offset = 11 and limit = 20, where 20 is the "last" row we want
* relative to offset (i.e. total number of rows = 20 - 11 = 9)
* <p/>
* So essentially, is limit relative from offset? Or is limit absolute?
*
* @return True if limit is relative from offset; false otherwise.
*/
public boolean useMaxForLimit() {
return false;
}
/**
* Given a limit and an offset, apply the limit clause to the query.
*
* @param query The query to which to apply the limit.
* @param offset The offset of the limit
* @param limit The limit of the limit ;)
* @return The modified query statement with the limit applied.
*/
public String getLimitString(String query, int offset, int limit) {
return getLimitString( query, offset > 0 );
}
/**
* Apply s limit clause to the query.
* <p/>
* Typically dialects utilize {@link #supportsVariableLimit() variable}
* limit caluses when they support limits. Thus, when building the
* select command we do not actually need to know the limit or the offest
* since we will just be using placeholders.
* <p/>
* Here we do still pass along whether or not an offset was specified
* so that dialects not supporting offsets can generate proper exceptions.
* In general, dialects will override one or the other of this method and
* {@link #getLimitString(String, int, int)}.
*
* @param query The query to which to apply the limit.
* @param hasOffset Is the query requesting an offset?
* @return the modified SQL
*/
protected String getLimitString(String query, boolean hasOffset) {
throw new UnsupportedOperationException( "paged queries not supported" );
}
// lock acquisition support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Get a strategy instance which knows how to acquire a database-level lock
* of the specified mode for this dialect.
*
* @param lockable The persister for the entity to be locked.
* @param lockMode The type of lock to be acquired.
* @return The appropriate locking strategy.
* @since 3.2
*/
public LockingStrategy getLockingStrategy(Lockable lockable, LockMode lockMode) {
return new SelectLockingStrategy( lockable, lockMode );
}
/**
* Given a lock mode, determine the appropriate for update fragment to use.
*
* @param lockMode The lock mode to apply.
* @return The appropriate for update fragment.
*/
public String getForUpdateString(LockMode lockMode) {
if ( lockMode==LockMode.UPGRADE ) {
return getForUpdateString();
}
else if ( lockMode==LockMode.UPGRADE_NOWAIT ) {
return getForUpdateNowaitString();
}
else if ( lockMode==LockMode.FORCE ) {
return getForUpdateNowaitString();
}
else {
return "";
}
}
/**
* Get the string to append to SELECT statements to acquire locks
* for this dialect.
*
* @return The appropriate <tt>FOR UPDATE</tt> clause string.
*/
public String getForUpdateString() {
return " for update";
}
/**
* Is <tt>FOR UPDATE OF</tt> syntax supported?
*
* @return True if the database supports <tt>FOR UPDATE OF</tt> syntax;
* false otherwise.
*/
public boolean forUpdateOfColumns() {
// by default we report no support
return false;
}
/**
* Does this dialect support <tt>FOR UPDATE</tt> in conjunction with
* outer joined rows?
*
* @return True if outer joined rows can be locked via <tt>FOR UPDATE</tt>.
*/
public boolean supportsOuterJoinForUpdate() {
return true;
}
/**
* Get the <tt>FOR UPDATE OF column_list</tt> fragment appropriate for this
* dialect given the aliases of the columns to be write locked.
*
* @param aliases The columns to be write locked.
* @return The appropriate <tt>FOR UPDATE OF column_list</tt> clause string.
*/
public String getForUpdateString(String aliases) {
// by default we simply return the getForUpdateString() result since
// the default is to say no support for "FOR UPDATE OF ..."
return getForUpdateString();
}
/**
* Retrieves the <tt>FOR UPDATE NOWAIT</tt> syntax specific to this dialect.
*
* @return The appropriate <tt>FOR UPDATE NOWAIT</tt> clause string.
*/
public String getForUpdateNowaitString() {
// by default we report no support for NOWAIT lock semantics
return getForUpdateString();
}
/**
* Get the <tt>FOR UPDATE OF column_list NOWAIT</tt> fragment appropriate
* for this dialect given the aliases of the columns to be write locked.
*
* @param aliases The columns to be write locked.
* @return The appropriate <tt>FOR UPDATE colunm_list NOWAIT</tt> clause string.
*/
public String getForUpdateNowaitString(String aliases) {
return getForUpdateString( aliases );
}
/**
* Some dialects support an alternative means to <tt>SELECT FOR UPDATE</tt>,
* whereby a "lock hint" is appends to the table name in the from clause.
* <p/>
* contributed by <a href="http://sourceforge.net/users/heschulz">Helge Schulz</a>
*
* @param mode The lock mode to apply
* @param tableName The name of the table to which to apply the lock hint.
* @return The table with any required lock hints.
*/
public String appendLockHint(LockMode mode, String tableName) {
return tableName;
}
/**
* Modifies the given SQL by applying the appropriate updates for the specified
* lock modes and key columns.
* <p/>
* The behavior here is that of an ANSI SQL <tt>SELECT FOR UPDATE</tt>. This
* method is really intended to allow dialects which do not support
* <tt>SELECT FOR UPDATE</tt> to achieve this in their own fashion.
*
* @param sql the SQL string to modify
* @param aliasedLockModes a map of lock modes indexed by aliased table names.
* @param keyColumnNames a map of key columns indexed by aliased table names.
* @return the modified SQL string.
*/
public String applyLocksToSql(String sql, Map aliasedLockModes, Map keyColumnNames) {
return sql + new ForUpdateFragment( this, aliasedLockModes, keyColumnNames ).toFragmentString();
}
// table support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Command used to create a table.
*
* @return The command used to create a table.
*/
public String getCreateTableString() {
return "create table";
}
/**
* Slight variation on {@link #getCreateTableString}. Here, we have the
* command used to create a table when there is no primary key and
* duplicate rows are expected.
* <p/>
* Most databases do not care about the distinction; originally added for
* Teradata support which does care.
*
* @return The command used to create a multiset table.
*/
public String getCreateMultisetTableString() {
return getCreateTableString();
}
// temporary table support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support temporary tables?
*
* @return True if temp tables are supported; false otherwise.
*/
public boolean supportsTemporaryTables() {
return false;
}
/**
* Generate a temporary table name given the bas table.
*
* @param baseTableName The table name from which to base the temp table name.
* @return The generated temp table name.
*/
public String generateTemporaryTableName(String baseTableName) {
return "HT_" + baseTableName;
}
/**
* Command used to create a temporary table.
*
* @return The command used to create a temporary table.
*/
public String getCreateTemporaryTableString() {
return "create table";
}
/**
* Get any fragments needing to be postfixed to the command for
* temporary table creation.
*
* @return Any required postfix.
*/
public String getCreateTemporaryTablePostfix() {
return "";
}
/**
* Does the dialect require that temporary table DDL statements occur in
* isolation from other statements? This would be the case if the creation
* would cause any current transaction to get committed implicitly.
* <p/>
* JDBC defines a standard way to query for this information via the
* {@link java.sql.DatabaseMetaData#dataDefinitionCausesTransactionCommit()}
* method. However, that does not distinguish between temporary table
* DDL and other forms of DDL; MySQL, for example, reports DDL causing a
* transaction commit via its driver, even though that is not the case for
* temporary table DDL.
* <p/>
* Possible return values and their meanings:<ul>
* <li>{@link Boolean#TRUE} - Unequivocally, perform the temporary table DDL
* in isolation.</li>
* <li>{@link Boolean#FALSE} - Unequivocally, do <b>not</b> perform the
* temporary table DDL in isolation.</li>
* <li><i>null</i> - defer to the JDBC driver response in regards to
* {@link java.sql.DatabaseMetaData#dataDefinitionCausesTransactionCommit()}</li>
* </ul>
*
* @return see the result matrix above.
*/
public Boolean performTemporaryTableDDLInIsolation() {
return null;
}
/**
* Do we need to drop the temporary table after use?
*
* @return True if the table should be dropped.
*/
public boolean dropTemporaryTableAfterUse() {
return true;
}
// callable statement support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Registers an OUT parameter which will be returing a
* {@link java.sql.ResultSet}. How this is accomplished varies greatly
* from DB to DB, hence its inclusion (along with {@link #getResultSet}) here.
*
* @param statement The callable statement.
* @param position The bind position at which to register the OUT param.
* @return The number of (contiguous) bind positions used.
* @throws SQLException Indicates problems registering the OUT param.
*/
public int registerResultSetOutParameter(CallableStatement statement, int position) throws SQLException {
throw new UnsupportedOperationException(
getClass().getName() +
" does not support resultsets via stored procedures"
);
}
/**
* Given a callable statement previously processed by {@link #registerResultSetOutParameter},
* extract the {@link java.sql.ResultSet} from the OUT parameter.
*
* @param statement The callable statement.
* @return The extracted result set.
* @throws SQLException Indicates problems extracting the result set.
*/
public ResultSet getResultSet(CallableStatement statement) throws SQLException {
throw new UnsupportedOperationException(
getClass().getName() +
" does not support resultsets via stored procedures"
);
}
// current timestamp support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support a way to retrieve the database's current
* timestamp value?
*
* @return True if the current timestamp can be retrieved; false otherwise.
*/
public boolean supportsCurrentTimestampSelection() {
return false;
}
/**
* Should the value returned by {@link #getCurrentTimestampSelectString}
* be treated as callable. Typically this indicates that JDBC escape
* sytnax is being used...
*
* @return True if the {@link #getCurrentTimestampSelectString} return
* is callable; false otherwise.
*/
public boolean isCurrentTimestampSelectStringCallable() {
throw new UnsupportedOperationException( "Database not known to define a current timestamp function" );
}
/**
* Retrieve the command used to retrieve the current timestammp from the
* database.
*
* @return The command.
*/
public String getCurrentTimestampSelectString() {
throw new UnsupportedOperationException( "Database not known to define a current timestamp function" );
}
/**
* The name of the database-specific SQL function for retrieving the
* current timestamp.
*
* @return The function name.
*/
public String getCurrentTimestampSQLFunctionName() {
// the standard SQL function name is current_timestamp...
return "current_timestamp";
}
// SQLException support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Build an instance of the SQLExceptionConverter preferred by this dialect for
* converting SQLExceptions into Hibernate's JDBCException hierarchy. The default
* Dialect implementation simply returns a converter based on X/Open SQLState codes.
* <p/>
* It is strongly recommended that specific Dialect implementations override this
* method, since interpretation of a SQL error is much more accurate when based on
* the ErrorCode rather than the SQLState. Unfortunately, the ErrorCode is a vendor-
* specific approach.
*
* @return The Dialect's preferred SQLExceptionConverter.
*/
public SQLExceptionConverter buildSQLExceptionConverter() {
// The default SQLExceptionConverter for all dialects is based on SQLState
// since SQLErrorCode is extremely vendor-specific. Specific Dialects
// may override to return whatever is most appropriate for that vendor.
return new SQLStateConverter( getViolatedConstraintNameExtracter() );
}
private static final ViolatedConstraintNameExtracter EXTRACTER = new ViolatedConstraintNameExtracter() {
public String extractConstraintName(SQLException sqle) {
return null;
}
};
public ViolatedConstraintNameExtracter getViolatedConstraintNameExtracter() {
return EXTRACTER;
}
// union subclass support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Given a {@link java.sql.Types} type code, determine an appropriate
* null value to use in a select clause.
* <p/>
* One thing to consider here is that certain databases might
* require proper casting for the nulls here since the select here
* will be part of a UNION/UNION ALL.
*
* @param sqlType The {@link java.sql.Types} type code.
* @return The appropriate select clause value fragment.
*/
public String getSelectClauseNullString(int sqlType) {
return "null";
}
/**
* Does this dialect support UNION ALL, which is generally a faster
* variant of UNION?
*
* @return True if UNION ALL is supported; false otherwise.
*/
public boolean supportsUnionAll() {
return false;
}
// miscellaneous support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Create a {@link org.hibernate.sql.JoinFragment} strategy responsible
* for handling this dialect's variations in how joins are handled.
*
* @return This dialect's {@link org.hibernate.sql.JoinFragment} strategy.
*/
public JoinFragment createOuterJoinFragment() {
return new ANSIJoinFragment();
}
/**
* Create a {@link org.hibernate.sql.CaseFragment} strategy responsible
* for handling this dialect's variations in how CASE statements are
* handled.
*
* @return This dialect's {@link org.hibernate.sql.CaseFragment} strategy.
*/
public CaseFragment createCaseFragment() {
return new ANSICaseFragment();
}
/**
* The fragment used to insert a row without specifying any column values.
* This is not possible on some databases.
*
* @return The appropriate empty values clause.
*/
public String getNoColumnsInsertString() {
return "values ( )";
}
/**
* The name of the SQL function that transforms a string to
* lowercase
*
* @return The dialect-specific lowercase function.
*/
public String getLowercaseFunction() {
return "lower";
}
/**
* Meant as a means for end users to affect the select strings being sent
* to the database and perhaps manipulate them in some fashion.
* <p/>
* The recommend approach is to instead use
* {@link org.hibernate.Interceptor#onPrepareStatement(String)}.
*
* @param select The select command
* @return The mutated select command, or the same as was passed in.
*/
public String transformSelectString(String select) {
return select;
}
/**
* What is the maximum length Hibernate can use for generated aliases?
*
* @return The maximum length.
*/
public int getMaxAliasLength() {
return 10;
}
/**
* The SQL literal value to which this database maps boolean values.
*
* @param bool The boolean value
* @return The appropriate SQL literal.
*/
public String toBooleanValueString(boolean bool) {
return bool ? "1" : "0";
}
// identifier quoting support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* The character specific to this dialect used to begin a quoted identifier.
*
* @return The dialect's specific open quote character.
*/
public char openQuote() {
return '"';
}
/**
* The character specific to this dialect used to close a quoted identifier.
*
* @return The dialect's specific close quote character.
*/
public char closeQuote() {
return '"';
}
/**
* Apply dialect-specific quoting.
* <p/>
* By default, the incoming value is checked to see if its first character
* is the back-tick (`). If so, the dialect specific quoting is applied.
*
* @param column The value to be quoted.
* @return The quoted (or unmodified, if not starting with back-tick) value.
* @see #openQuote()
* @see #closeQuote()
*/
public final String quote(String column) {
if ( column.charAt( 0 ) == '`' ) {
return openQuote() + column.substring( 1, column.length() - 1 ) + closeQuote();
}
else {
return column;
}
}
// DDL support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support the <tt>ALTER TABLE</tt> syntax?
*
* @return True if we support altering of tables; false otherwise.
*/
public boolean hasAlterTable() {
return true;
}
/**
* Do we need to drop constraints before dropping tables in this dialect?
*
* @return True if constraints must be dropped prior to dropping
* the table; false otherwise.
*/
public boolean dropConstraints() {
return true;
}
/**
* Do we need to qualify index names with the schema name?
*
* @return boolean
*/
public boolean qualifyIndexName() {
return true;
}
/**
* Does this dialect support the <tt>UNIQUE</tt> column syntax?
*
* @return boolean
*/
public boolean supportsUnique() {
return true;
}
/**
* Does this dialect support adding Unique constraints via create and alter table ?
* @return boolean
*/
public boolean supportsUniqueConstraintInCreateAlterTable() {
return true;
}
/**
* The syntax used to add a column to a table (optional).
*
* @return The "add column" fragment.
*/
public String getAddColumnString() {
throw new UnsupportedOperationException( "No add column syntax supported by Dialect" );
}
public String getDropForeignKeyString() {
return " drop constraint ";
}
public String getTableTypeString() {
// grrr... for differentiation of mysql storage engines
return "";
}
/**
* The syntax used to add a foreign key constraint to a table.
*
* @param constraintName The FK constraint name.
* @param foreignKey The names of the columns comprising the FK
* @param referencedTable The table referenced by the FK
* @param primaryKey The explicit columns in the referencedTable referenced
* by this FK.
* @param referencesPrimaryKey if false, constraint should be
* explicit about which column names the constraint refers to
*
* @return the "add FK" fragment
*/
public String getAddForeignKeyConstraintString(
String constraintName,
String[] foreignKey,
String referencedTable,
String[] primaryKey,
boolean referencesPrimaryKey) {
StringBuffer res = new StringBuffer( 30 );
res.append( " add constraint " )
.append( constraintName )
.append( " foreign key (" )
.append( StringHelper.join( ", ", foreignKey ) )
.append( ") references " )
.append( referencedTable );
if ( !referencesPrimaryKey ) {
res.append( " (" )
.append( StringHelper.join( ", ", primaryKey ) )
.append( ')' );
}
return res.toString();
}
/**
* The syntax used to add a primary key constraint to a table.
*
* @param constraintName The name of the PK constraint.
* @return The "add PK" fragment
*/
public String getAddPrimaryKeyConstraintString(String constraintName) {
return " add constraint " + constraintName + " primary key ";
}
public boolean hasSelfReferentialForeignKeyBug() {
return false;
}
/**
* The keyword used to specify a nullable column.
*
* @return String
*/
public String getNullColumnString() {
return "";
}
public boolean supportsCommentOn() {
return false;
}
public String getTableComment(String comment) {
return "";
}
public String getColumnComment(String comment) {
return "";
}
public boolean supportsIfExistsBeforeTableName() {
return false;
}
public boolean supportsIfExistsAfterTableName() {
return false;
}
/**
* Does this dialect support column-level check constraints?
*
* @return True if column-level CHECK constraints are supported; false
* otherwise.
*/
public boolean supportsColumnCheck() {
return true;
}
/**
* Does this dialect support table-level check constraints?
*
* @return True if table-level CHECK constraints are supported; false
* otherwise.
*/
public boolean supportsTableCheck() {
return true;
}
public boolean supportsCascadeDelete() {
return true;
}
public boolean supportsNotNullUnique() {
return true;
}
/**
* Completely optional cascading drop clause
*
* @return String
*/
public String getCascadeConstraintsString() {
return "";
}
// Informational metadata ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/**
* Does this dialect support empty IN lists?
* <p/>
* For example, is [where XYZ in ()] a supported construct?
*
* @return True if empty in lists are supported; false otherwise.
* @since 3.2
*/
public boolean supportsEmptyInList() {
return true;
}
/**
* Are string comparisons implicitly case insensitive.
* <p/>
* In other words, does [where 'XYZ' = 'xyz'] resolve to true?
*
* @return True if comparisons are case insensitive.
* @since 3.2
*/
public boolean areStringComparisonsCaseInsensitive() {
return false;
}
/**
* Is this dialect known to support what ANSI-SQL terms "row value
* constructor" syntax; sometimes called tuple syntax.
* <p/>
* Basically, does it support syntax like
* "... where (FIRST_NAME, LAST_NAME) = ('Steve', 'Ebersole') ...".
*
* @return True if this SQL dialect is known to support "row value
* constructor" syntax; false otherwise.
* @since 3.2
*/
public boolean supportsRowValueConstructorSyntax() {
// return false here, as most databases do not properly support this construct...
return false;
}
/**
* If the dialect supports {@link #supportsRowValueConstructorSyntax() row values},
* does it offer such support in IN lists as well?
* <p/>
* For example, "... where (FIRST_NAME, LAST_NAME) IN ( (?, ?), (?, ?) ) ..."
*
* @return True if this SQL dialect is known to support "row value
* constructor" syntax in the IN list; false otherwise.
* @since 3.2
*/
public boolean supportsRowValueConstructorSyntaxInInList() {
return false;
}
/**
* Should LOBs (both BLOB and CLOB) be bound using stream operations (i.e.
* {@link java.sql.PreparedStatement#setBinaryStream}).
*
* @return True if BLOBs and CLOBs should be bound using stream operations.
* @since 3.2
*/
public boolean useInputStreamToInsertBlob() {
return true;
}
/**
* Does this dialect support parameters within the select clause of
* INSERT ... SELECT ... statements?
*
* @return True if this is supported; false otherwise.
* @since 3.2
*/
public boolean supportsParametersInInsertSelect() {
return true;
}
/**
* Does this dialect support asking the result set its positioning
* information on forward only cursors. Specifically, in the case of
* scrolling fetches, Hibernate needs to use
* {@link java.sql.ResultSet#isAfterLast} and
* {@link java.sql.ResultSet#isBeforeFirst}. Certain drivers do not
* allow access to these methods for forward only cursors.
* <p/>
* NOTE : this is highly driver dependent!
*
* @return True if methods like {@link java.sql.ResultSet#isAfterLast} and
* {@link java.sql.ResultSet#isBeforeFirst} are supported for forward
* only cursors; false otherwise.
* @since 3.2
*/
public boolean supportsResultSetPositionQueryMethodsOnForwardOnlyCursor() {
return true;
}
/**
* Does this dialect support definition of cascade delete constraints
* which can cause circular chains?
*
* @return True if circular cascade delete constraints are supported; false
* otherwise.
* @since 3.2
*/
public boolean supportsCircularCascadeDeleteConstraints() {
return true;
}
/**
* Are subselects supported as the left-hand-side (LHS) of
* IN-predicates.
* <p/>
* In other words, is syntax like "... <subquery> IN (1, 2, 3) ..." supported?
*
* @return True if subselects can appear as the LHS of an in-predicate;
* false otherwise.
* @since 3.2
*/
public boolean supportsSubselectAsInPredicateLHS() {
return true;
}
/**
* Expected LOB usage pattern is such that I can perform an insert
* via prepared statement with a parameter binding for a LOB value
* without crazy casting to JDBC driver implementation-specific classes...
* <p/>
* Part of the trickiness here is the fact that this is largely
* driver dependent. For example, Oracle (which is notoriously bad with
* LOB support in their drivers historically) actually does a pretty good
* job with LOB support as of the 10.2.x versions of their drivers...
*
* @return True if normal LOB usage patterns can be used with this driver;
* false if driver-specific hookiness needs to be applied.
* @since 3.2
*/
public boolean supportsExpectedLobUsagePattern() {
return true;
}
/**
* Does the dialect support propogating changes to LOB
* values back to the database? Talking about mutating the
* internal value of the locator as opposed to supplying a new
* locator instance...
* <p/>
* For BLOBs, the internal value might be changed by:
* {@link java.sql.Blob#setBinaryStream},
* {@link java.sql.Blob#setBytes(long, byte[])},
* {@link java.sql.Blob#setBytes(long, byte[], int, int)},
* or {@link java.sql.Blob#truncate(long)}.
* <p/>
* For CLOBs, the internal value might be changed by:
* {@link java.sql.Clob#setAsciiStream(long)},
* {@link java.sql.Clob#setCharacterStream(long)},
* {@link java.sql.Clob#setString(long, String)},
* {@link java.sql.Clob#setString(long, String, int, int)},
* or {@link java.sql.Clob#truncate(long)}.
* <p/>
* NOTE : I do not know the correct answer currently for
* databases which (1) are not part of the cruise control process
* or (2) do not {@link #supportsExpectedLobUsagePattern}.
*
* @return True if the changes are propogated back to the
* database; false otherwise.
* @since 3.2
*/
public boolean supportsLobValueChangePropogation() {
return true;
}
/**
* Is it supported to materialize a LOB locator outside the transaction in
* which it was created?
* <p/>
* Again, part of the trickiness here is the fact that this is largely
* driver dependent.
* <p/>
* NOTE: all database I have tested which {@link #supportsExpectedLobUsagePattern()}
* also support the ability to materialize a LOB outside the owning transaction...
*
* @return True if unbounded materialization is supported; false otherwise.
* @since 3.2
*/
public boolean supportsUnboundedLobLocatorMaterialization() {
return true;
}
/**
* Does this dialect support referencing the table being mutated in
* a subquery. The "table being mutated" is the table referenced in
* an UPDATE or a DELETE query. And so can that table then be
* referenced in a subquery of said UPDATE/DELETE query.
* <p/>
* For example, would the following two syntaxes be supported:<ul>
* <li>delete from TABLE_A where ID not in ( select ID from TABLE_A )</li>
* <li>update TABLE_A set NON_ID = 'something' where ID in ( select ID from TABLE_A)</li>
* </ul>
*
* @return True if this dialect allows references the mutating table from
* a subquery.
* @since 3.2
*/
public boolean supportsSubqueryOnMutatingTable() {
return true;
}
/**
* Does the dialect support an exists statement in the select clause?
*
* @return True if exists checks are allowed in the select clause; false otherwise.
*/
public boolean supportsExistsInSelect() {
return true;
}
/**
* For the underlying database, is READ_COMMITTED isolation implemented by
* forcing readers to wait for write locks to be released?
*
* @return True if writers block readers to achieve READ_COMMITTED; false otherwise.
*/
public boolean doesReadCommittedCauseWritersToBlockReaders() {
return false;
}
/**
* For the underlying database, is REPEATABLE_READ isolation implemented by
* forcing writers to wait for read locks to be released?
*
* @return True if readers block writers to achieve REPEATABLE_READ; false otherwise.
*/
public boolean doesRepeatableReadCauseReadersToBlockWriters() {
return false;
}
/**
* Does this dialect support using a JDBC bind parameter as an argument
* to a function or procedure call?
*
* @return True if the database supports accepting bind params as args; false otherwise.
*/
public boolean supportsBindAsCallableArgument() {
return true;
}
}
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