abstractjdbc1databasemetadata.java

来自「PostgreSQL7.4.6 for Linux」· Java 代码 · 共 2,128 行 · 第 1/5 页

			Driver.debug("storesMixedCaseQuotedIdentifiers " + false);
		return false;
	}

	/*
	 * What is the string used to quote SQL identifiers?  This returns
	 * a space if identifier quoting isn't supported.  A JDBC Compliant
	 * driver will always use a double quote character.
	 *
	 * @return the quoting string
	 * @exception SQLException if a database access error occurs
	 */
	public String getIdentifierQuoteString() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getIdentifierQuoteString \"" );
		return "\"";
	}

	/*
	 * Get a comma separated list of all a database's SQL keywords that
	 * are NOT also SQL92 keywords.
	 *
	 * <p>Within PostgreSQL, the keywords are found in
	 *	src/backend/parser/keywords.c
	 *
	 * <p>For SQL Keywords, I took the list provided at
	 *	<a href="http://web.dementia.org/~shadow/sql/sql3bnf.sep93.txt">
	 * http://web.dementia.org/~shadow/sql/sql3bnf.sep93.txt</a>
	 * which is for SQL3, not SQL-92, but it is close enough for
	 * this purpose.
	 *
	 * @return a comma separated list of keywords we use
	 * @exception SQLException if a database access error occurs
	 */
	public String getSQLKeywords() throws SQLException
	{
		return keywords;
	}

	public String getNumericFunctions() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getNumericFunctions");
		return "";
	}

	public String getStringFunctions() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getStringFunctions");
		return "";
	}

	public String getSystemFunctions() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getSystemFunctions");
		return "";
	}

	public String getTimeDateFunctions() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getTimeDateFunctions");
		return "";
	}

	/*
	 * This is the string that can be used to escape '_' and '%' in
	 * a search string pattern style catalog search parameters
	 *
	 * @return the string used to escape wildcard characters
	 * @exception SQLException if a database access error occurs
	 */
	public String getSearchStringEscape() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getSearchStringEscape");
		return "\\\\";
	}

	/*
	 * Get all the "extra" characters that can be used in unquoted
	 * identifier names (those beyond a-zA-Z0-9 and _)
	 *
	 * <p>From the file src/backend/parser/scan.l, an identifier is
	 * {letter}{letter_or_digit} which makes it just those listed
	 * above.
	 *
	 * @return a string containing the extra characters
	 * @exception SQLException if a database access error occurs
	 */
	public String getExtraNameCharacters() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("getExtraNameCharacters");
		return "";
	}

	/*
	 * Is "ALTER TABLE" with an add column supported?
	 * Yes for PostgreSQL 6.1
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsAlterTableWithAddColumn() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsAlterTableWithAddColumn " + true);
		return true;
	}

	/*
	 * Is "ALTER TABLE" with a drop column supported?
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsAlterTableWithDropColumn() throws SQLException
	{
		boolean dropColumn = connection.haveMinimumServerVersion("7.3");
		if (Driver.logDebug)
			Driver.debug("supportsAlterTableWithDropColumn " + dropColumn);
		return dropColumn;
	}

	/*
	 * Is column aliasing supported?
	 *
	 * <p>If so, the SQL AS clause can be used to provide names for
	 * computed columns or to provide alias names for columns as
	 * required.  A JDBC Compliant driver always returns true.
	 *
	 * <p>e.g.
	 *
	 * <br><pre>
	 * select count(C) as C_COUNT from T group by C;
	 *
	 * </pre><br>
	 * should return a column named as C_COUNT instead of count(C)
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsColumnAliasing() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsColumnAliasing " + true);
		return true;
	}

	/*
	 * Are concatenations between NULL and non-NULL values NULL?  A
	 * JDBC Compliant driver always returns true
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean nullPlusNonNullIsNull() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("nullPlusNonNullIsNull " + true);
		return true;
	}

	public boolean supportsConvert() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsConvert " + false);
		return false;
	}

	public boolean supportsConvert(int fromType, int toType) throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsConvert " + false);
		return false;
	}

	/*
	 * Are table correlation names supported? A JDBC Compliant
	 * driver always returns true.
	 *
	 * @return true if so; false otherwise
	 * @exception SQLException - if a database access error occurs
	 */
	public boolean supportsTableCorrelationNames() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsTableCorrelationNames " + true);
		return true;
	}

	/*
	 * If table correlation names are supported, are they restricted to
	 * be different from the names of the tables?
	 *
	 * @return true if so; false otherwise
	 * @exception SQLException - if a database access error occurs
	 */
	public boolean supportsDifferentTableCorrelationNames() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsDifferentTableCorrelationNames " + false);
		return false;
	}

	/*
	 * Are expressions in "ORDER BY" lists supported?
	 *
	 * <br>e.g. select * from t order by a + b;
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsExpressionsInOrderBy() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsExpressionsInOrderBy " + true);
		return true;
	}

	/*
	 * Can an "ORDER BY" clause use columns not in the SELECT?
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsOrderByUnrelated() throws SQLException
	{
		boolean supportsOrderByUnrelated = connection.haveMinimumServerVersion("6.4");
		if (Driver.logDebug)
			Driver.debug("supportsOrderByUnrelated " + supportsOrderByUnrelated);
		return supportsOrderByUnrelated;
	}

	/*
	 * Is some form of "GROUP BY" clause supported?
	 * I checked it, and yes it is.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsGroupBy() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsGroupBy " + true);
		return true;
	}

	/*
	 * Can a "GROUP BY" clause use columns not in the SELECT?
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsGroupByUnrelated() throws SQLException
	{
		boolean supportsGroupByUnrelated = connection.haveMinimumServerVersion("6.4");
		if (Driver.logDebug)
			Driver.debug("supportsGroupByUnrelated " + supportsGroupByUnrelated);
		return supportsGroupByUnrelated;
	}

	/*
	 * Can a "GROUP BY" clause add columns not in the SELECT provided
	 * it specifies all the columns in the SELECT?	Does anyone actually
	 * understand what they mean here?
	 *
	 * (I think this is a subset of the previous function. -- petere)
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsGroupByBeyondSelect() throws SQLException
	{
		boolean supportsGroupByBeyondSelect = connection.haveMinimumServerVersion("6.4");
		if (Driver.logDebug)
			Driver.debug("supportsGroupByUnrelated " + supportsGroupByBeyondSelect);
		return supportsGroupByBeyondSelect;
	}

	/*
	 * Is the escape character in "LIKE" clauses supported?  A
	 * JDBC compliant driver always returns true.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsLikeEscapeClause() throws SQLException
	{
		boolean supportsLikeEscapeClause = connection.haveMinimumServerVersion("7.1");
		if (Driver.logDebug)
			Driver.debug("supportsLikeEscapeClause " + supportsLikeEscapeClause);
		return supportsLikeEscapeClause;
	}

	/*
	 * Are multiple ResultSets from a single execute supported?
	 * Well, I implemented it, but I dont think this is possible from
	 * the back ends point of view.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsMultipleResultSets() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsMultipleResultSets " + false);
		return false;
	}

	/*
	 * Can we have multiple transactions open at once (on different
	 * connections?)
	 * I guess we can have, since Im relying on it.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsMultipleTransactions() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsMultipleTransactions " + true);
		return true;
	}

	/*
	 * Can columns be defined as non-nullable.	A JDBC Compliant driver
	 * always returns true.
	 *
	 * <p>This changed from false to true in v6.2 of the driver, as this
	 * support was added to the backend.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsNonNullableColumns() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsNonNullableColumns true");
		return true;
	}

	/*
	 * Does this driver support the minimum ODBC SQL grammar.  This
	 * grammar is defined at:
	 *
	 * <p><a href="http://www.microsoft.com/msdn/sdk/platforms/doc/odbc/src/intropr.htm">http://www.microsoft.com/msdn/sdk/platforms/doc/odbc/src/intropr.htm</a>
	 *
	 * <p>In Appendix C.  From this description, we seem to support the
	 * ODBC minimal (Level 0) grammar.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsMinimumSQLGrammar() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsMinimumSQLGrammar TRUE");
		return true;
	}

	/*
	 * Does this driver support the Core ODBC SQL grammar.	We need
	 * SQL-92 conformance for this.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsCoreSQLGrammar() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsCoreSQLGrammar FALSE ");
		return false;
	}

	/*
	 * Does this driver support the Extended (Level 2) ODBC SQL
	 * grammar.  We don't conform to the Core (Level 1), so we can't
	 * conform to the Extended SQL Grammar.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsExtendedSQLGrammar() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsExtendedSQLGrammar FALSE");
		return false;
	}

	/*
	 * Does this driver support the ANSI-92 entry level SQL grammar?
	 * All JDBC Compliant drivers must return true. We currently
	 * report false until 'schema' support is added.  Then this
	 * should be changed to return true, since we will be mostly
	 * compliant (probably more compliant than many other databases)
	 * And since this is a requirement for all JDBC drivers we
	 * need to get to the point where we can return true.
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsANSI92EntryLevelSQL() throws SQLException
	{
		boolean schemas = connection.haveMinimumServerVersion("7.3");
		if (Driver.logDebug)
			Driver.debug("supportsANSI92EntryLevelSQL " + schemas);
		return schemas;
	}

	/*
	 * Does this driver support the ANSI-92 intermediate level SQL
	 * grammar?
	 *
	 * @return true if so
	 * @exception SQLException if a database access error occurs
	 */
	public boolean supportsANSI92IntermediateSQL() throws SQLException
	{
		if (Driver.logDebug)
			Driver.debug("supportsANSI92IntermediateSQL false ");
		return false;