databasemetadata.java

关系型数据库 Postgresql 6.5.2

package postgresql.jdbc1;

// IMPORTANT NOTE: This file implements the JDBC 1 version of the driver.
// If you make any modifications to this file, you must make sure that the
// changes are also made (if relevent) to the related JDBC 2 class in the
// postgresql.jdbc2 package.

import java.sql.*;
import java.util.*;
import postgresql.Field;

/**
 * This class provides information about the database as a whole.
 *
 * <p>Many of the methods here return lists of information in ResultSets.  You
 * can use the normal ResultSet methods such as getString and getInt to 
 * retrieve the data from these ResultSets.  If a given form of metadata is
 * not available, these methods should throw a SQLException.
 *
 * <p>Some of these methods take arguments that are String patterns.  These
 * arguments all have names such as fooPattern.  Within a pattern String,
 * "%" means match any substring of 0 or more characters, and "_" means
 * match any one character.  Only metadata entries matching the search
 * pattern are returned.  if a search pattern argument is set to a null
 * ref, it means that argument's criteria should be dropped from the
 * search.
 *
 * <p>A SQLException will be throws if a driver does not support a meta
 * data method.  In the case of methods that return a ResultSet, either
 * a ResultSet (which may be empty) is returned or a SQLException is
 * thrown.
 *
 * @see java.sql.DatabaseMetaData
 */
public class DatabaseMetaData implements java.sql.DatabaseMetaData 
{
  Connection connection;		// The connection association
  
  // These define various OID's. Hopefully they will stay constant.
  static final int iVarcharOid = 1043;	// OID for varchar
  static final int iBoolOid = 16;	// OID for bool
  static final int iInt2Oid = 21;	// OID for int2
  static final int iInt4Oid = 23;	// OID for int4
  static final int VARHDRSZ =  4;	// length for int4
  
  // This is a default value for remarks
  private static final byte defaultRemarks[]="no remarks".getBytes();
  
  public DatabaseMetaData(Connection conn)
  {
    this.connection = conn;
  }
  
  /**
   * Can all the procedures returned by getProcedures be called
   * by the current user?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean allProceduresAreCallable() throws SQLException
  {
    return true;		// For now...
  }
  
  /**
   * Can all the tables returned by getTable be SELECTed by
   * the current user?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean allTablesAreSelectable() throws SQLException
  {
    return true;		// For now...
  }
  
  /**
   * What is the URL for this database?
   *
   * @return the url or null if it cannott be generated
   * @exception SQLException if a database access error occurs
   */
  public String getURL() throws SQLException
  {
    return connection.getURL();
  }
  
  /**
   * What is our user name as known to the database?
   *
   * @return our database user name
   * @exception SQLException if a database access error occurs
   */
  public String getUserName() throws SQLException
  {
    return connection.getUserName();
  }
  
  /**
   * Is the database in read-only mode?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean isReadOnly() throws SQLException
  {
    return connection.isReadOnly();
  }
  
  /**
   * Are NULL values sorted high?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean nullsAreSortedHigh() throws SQLException
  {
    return false;
  }
  
  /**
   * Are NULL values sorted low?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean nullsAreSortedLow() throws SQLException
  {
    return false;
  }
  
  /**
   * Are NULL values sorted at the start regardless of sort order?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean nullsAreSortedAtStart() throws SQLException
  {
    return false;
  }
  
  /**
   * Are NULL values sorted at the end regardless of sort order?
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean nullsAreSortedAtEnd() throws SQLException
  {
    return true;
  }
  
  /**
   * What is the name of this database product - we hope that it is
   * PostgreSQL, so we return that explicitly.
   *
   * @return the database product name
   * @exception SQLException if a database access error occurs
   */
  public String getDatabaseProductName() throws SQLException
  {
    return new String("PostgreSQL");
  }
  
  /**
   * What is the version of this database product.
   *
   * <p>Note that PostgreSQL 6.3 has a system catalog called pg_version - 
   * however, select * from pg_version on any database retrieves
   * no rows.
   *
   * <p>For now, we will return the version 6.3 (in the hope that we change
   * this driver as often as we change the database)
   *
   * @return the database version
   * @exception SQLException if a database access error occurs
   */
  public String getDatabaseProductVersion() throws SQLException
  {
    return ("6.4");
  }
  
  /**
   * What is the name of this JDBC driver?  If we don't know this
   * we are doing something wrong!
   *
   * @return the JDBC driver name
   * @exception SQLException why?
   */
  public String getDriverName() throws SQLException
  {
    return new String("PostgreSQL Native Driver");
  }
  
  /**
   * What is the version string of this JDBC driver?  Again, this is
   * static.
   *
   * @return the JDBC driver name.
   * @exception SQLException why?
   */
  public String getDriverVersion() throws SQLException
  {
    return new String(Integer.toString(connection.this_driver.getMajorVersion())+"."+Integer.toString(connection.this_driver.getMinorVersion()));
  }
  
  /**
   * What is this JDBC driver's major version number?
   *
   * @return the JDBC driver major version
   */
  public int getDriverMajorVersion()
  {
    return connection.this_driver.getMajorVersion();
  }
  
  /**
   * What is this JDBC driver's minor version number?
   *
   * @return the JDBC driver minor version
   */
  public int getDriverMinorVersion()
  {
    return connection.this_driver.getMinorVersion();
  }
  
  /**
   * Does the database store tables in a local file?  No - it
   * stores them in a file on the server.
   * 
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean usesLocalFiles() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database use a file for each table?  Well, not really,
   * since it doesnt use local files. 
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean usesLocalFilePerTable() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case unquoted SQL identifiers
   * as case sensitive and as a result store them in mixed case?
   * A JDBC-Compliant driver will always return false.
   *
   * <p>Predicament - what do they mean by "SQL identifiers" - if it
   * means the names of the tables and columns, then the answers
   * given below are correct - otherwise I don't know.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsMixedCaseIdentifiers() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case unquoted SQL identifiers as
   * case insensitive and store them in upper case?
   *
   * @return true if so
   */
  public boolean storesUpperCaseIdentifiers() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case unquoted SQL identifiers as
   * case insensitive and store them in lower case?
   *
   * @return true if so
   */
  public boolean storesLowerCaseIdentifiers() throws SQLException
  {
    return true;
  }
  
  /**
   * Does the database treat mixed case unquoted SQL identifiers as
   * case insensitive and store them in mixed case?
   *
   * @return true if so
   */
  public boolean storesMixedCaseIdentifiers() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case quoted SQL identifiers as
   * case sensitive and as a result store them in mixed case?  A
   * JDBC compliant driver will always return true. 
   *
   * <p>Predicament - what do they mean by "SQL identifiers" - if it
   * means the names of the tables and columns, then the answers
   * given below are correct - otherwise I don't know.
   *
   * @return true if so
   * @exception SQLException if a database access error occurs
   */
  public boolean supportsMixedCaseQuotedIdentifiers() throws SQLException
  {
    return true;
  }
  
  /**
   * Does the database treat mixed case quoted SQL identifiers as
   * case insensitive and store them in upper case?
   *
   * @return true if so
   */
  public boolean storesUpperCaseQuotedIdentifiers() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case quoted SQL identifiers as case
   * insensitive and store them in lower case?
   *
   * @return true if so
   */
  public boolean storesLowerCaseQuotedIdentifiers() throws SQLException
  {
    return false;
  }
  
  /**
   * Does the database treat mixed case quoted SQL identifiers as case
   * insensitive and store them in mixed case?
   *
   * @return true if so
   */
  public boolean storesMixedCaseQuotedIdentifiers() throws SQLException
  {
    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.
   *
   * <p>If an SQL identifier is a table name, column name, etc. then
   * we do not support it.
   *
   * @return the quoting string
   * @exception SQLException if a database access error occurs
   */
  public String getIdentifierQuoteString() throws SQLException
  {
    return null;
  }
  
  /**
   * 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 new String("abort,acl,add,aggregate,append,archive,arch_store,backward,binary,change,cluster,copy,database,delimiters,do,extend,explain,forward,heavy,index,inherits,isnull,light,listen,load,merge,nothing,notify,notnull,oids,purge,rename,replace,retrieve,returns,rule,recipe,setof,stdin,stdout,store,vacuum,verbose,version");
  }
  
  public String getNumericFunctions() throws SQLException
  {
    // XXX-Not Implemented
    return "";
  }
  
  public String getStringFunctions() throws SQLException
  {
    // XXX-Not Implemented
    return "";
  }
  
  public String getSystemFunctions() throws SQLException
  {
    // XXX-Not Implemented
    return "";
  }
  
  public String getTimeDateFunctions() throws SQLException
  {
    // XXX-Not Implemented
    return "";
  }