Re: What needs to be done? - Mailing list pgsql-jdbc

Ricardo,

There are many other issues with postgres blobs that will not allow you
to acheive your goal easily.  You are going to need different
implementations per database type to deal with the differences between
blob implementations across different databases.  The one big hurdle you
will have with postgres blobs is the fact that when you delete the row
containing the blob, it doesn't delete the blob.  You have to issue a
separate delete blob request.  This is very different than what happens
in Oracle for example.  This can be automated by adding triggers to the
table to do this, but by now you are very far from having a single code
base (at least the code that creates the tables and triggers) that
supports all of the different databases.

thanks,
--Barry

Ricardo Maia wrote:

>
> So how whould I map the BLOB java type in the corresponding SQL type?
>
> I want to create a table with a BLOB attribute, but I want that my code can
> run for PostgreSQL, Oracle and other BD that handles BLOBs.
>
> So first I had to map the BLOB in the corresponding BD SQL type and then
> create the table with an attribute of that SQL type.
>
> Ricardo Maia
>
> On Thursday 02 August 2001 03:16, Barry Lind wrote:
>
>>I actually think the response for 'oid' is correct.  It reports the oid
>>as java type integer (which is the real datatype of the value stored).
>>A column of type oid can be used for may different things.  It can be
>>used for blobs, but not all columns of type oid are used for blobs.
>>Another use of a column of type oid is to store foreign keys from one
>>table to another.  Since all tables have a builtin column named 'oid' of
>>type oid, it is very convenient to use this value in foreign keys on
>>other tables.  Assuming that oid = blob would break those applications.
>>
>>I hope everyone that uses postgresql and jdbc understands that BLOB
>>support is one area with many problems, some of which can be fixed in
>>the JDBC code, but others that will require better support in the
>>underlying database.
>>
>>thanks,
>>--Barry
>>
>>Ricardo Maia wrote:
>>
>>>For example when I call the method:
>>>
>>>DatabaseMetaData.getTypeInfo()
>>>
>>>I whould expect to see the SQL Type BLOB mapped as an oid.
>>>
>>>see attach
>>>
>>>Ricardo Maia
>>>
>>>On Wednesday 01 August 2001 23:29, Rene Pijlman wrote:
>>>
>>>>On Wed, 1 Aug 2001 22:49:40 +0100, Ricardo Maia wrote:
>>>>
>>>>>The problem is that, as the PostgreSQL JDBC driver doesn't
>>>>>follow JDBC Standard I had to write some specific code for
>>>>>use it with PostgreSQL DB.
>>>>>
>>>>So what exactly are the deviations from the standard that you
>>>>encountered?
>>>>
>>>>Regards,
>>>>René Pijlman
>>>>
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>>>>
>>>>
>>>>------------------------------------------------------------------------
>>>>
>>>>package databasetest;
>>>>
>>>>import java.sql.*;
>>>>
>>>>public class GetTypesInfo {
>>>>
>>>> public static void main(String args[ ]) {
>>>>
>>>>   String url = "jdbc:postgresql://127.0.0.1/test";
>>>>
>>>>   Connection con;
>>>>
>>>>   DatabaseMetaData dbmd;
>>>>
>>>>   try {
>>>>     Class.forName("org.postgresql.Driver");
>>>>   } catch(java.lang.ClassNotFoundException e) {
>>>>     System.err.print("ClassNotFoundException: ");
>>>>     System.err.println(e.getMessage());
>>>>   }
>>>>
>>>>   try {
>>>>     con = DriverManager.getConnection(url,"bobby", "tareco");
>>>>
>>>>     dbmd = con.getMetaData();
>>>>
>>>>     ResultSet rs = dbmd.getTypeInfo();
>>>>
>>>>     while (rs.next()) {
>>>>
>>>>       String typeName = rs.getString("TYPE_NAME");
>>>>
>>>>       short dataType = rs.getShort("DATA_TYPE");
>>>>
>>>>       String createParams = rs.getString("CREATE_PARAMS");
>>>>
>>>>       int nullable = rs.getInt("NULLABLE");
>>>>
>>>>       boolean caseSensitive = rs.getBoolean("CASE_SENSITIVE");
>>>>
>>>>       if(dataType != java.sql.Types.OTHER)
>>>>       {
>>>>         System.out.println("DBMS type " + typeName + ":");
>>>>         System.out.println("     java.sql.Types:  "  +
>>>>typeName(dataType)); System.out.print("     parameters used to create:
>>>>");
>>>>         System.out.println(createParams);
>>>>         System.out.println("     nullable?:  "  + nullable);
>>>>         System.out.print("     case sensitive?:  ");
>>>>         System.out.println(caseSensitive);
>>>>         System.out.println("");
>>>>       }
>>>>     }
>>>>
>>>>     con.close();
>>>>   } catch(SQLException ex) {
>>>>     System.err.println("SQLException: " + ex.getMessage());
>>>>   }
>>>> }
>>>>
>>>>
>>>> public static String typeName(int i)
>>>> {
>>>>   switch(i){
>>>>     case java.sql.Types.ARRAY: return "ARRAY";
>>>>     case java.sql.Types.BIGINT: return "BIGINT";
>>>>     case java.sql.Types.BINARY: return "BINARY";
>>>>     case java.sql.Types.BIT: return "BIT";
>>>>     case java.sql.Types.BLOB: return "BLOB";
>>>>     case java.sql.Types.CHAR: return "CHAR";
>>>>     case java.sql.Types.CLOB: return "CLOB";
>>>>     case java.sql.Types.DATE: return "DATE";
>>>>     case java.sql.Types.DECIMAL: return "DECIMAL";
>>>>     case java.sql.Types.DISTINCT: return "DISTINCT";
>>>>     case java.sql.Types.DOUBLE: return "DOUBLE";
>>>>     case java.sql.Types.FLOAT: return "FLOAT";
>>>>     case java.sql.Types.INTEGER: return "INTEGER";
>>>>     case java.sql.Types.JAVA_OBJECT: return "JAVA_OBJECT";
>>>>     case java.sql.Types.LONGVARBINARY: return "LONGVARBINARY";
>>>>     case java.sql.Types.LONGVARCHAR: return "LONGVARCHAR";
>>>>     case java.sql.Types.NULL: return "NULL";
>>>>     case java.sql.Types.NUMERIC: return "NUMERIC";
>>>>     case java.sql.Types.OTHER: return "OTHER";
>>>>     case java.sql.Types.REAL: return "REAL";
>>>>     case java.sql.Types.REF: return "REF";
>>>>     case java.sql.Types.SMALLINT: return "SMALLINT";
>>>>     case java.sql.Types.STRUCT: return "STRUCT";
>>>>     case java.sql.Types.TIME: return "TIME";
>>>>     case java.sql.Types.TIMESTAMP: return "TIMESTAMP";
>>>>     case java.sql.Types.TINYINT: return "TINYINT";
>>>>     case java.sql.Types.VARBINARY: return "VARBINARY";
>>>>     case java.sql.Types.VARCHAR: return "VARCHAR";
>>>>     default: return "";
>>>>   }
>>>> }
>>>>}
>>>>
>>>>
>>>>------------------------------------------------------------------------
>>>>
>>>>
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>>>>
>>>>http://www.postgresql.org/users-lounge/docs/faq.html
>>>>
>>>>GetTypesInfo.java
>>>>
>>>>Content-Type:
>>>>
>>>>text/x-java
>>>>Content-Encoding:
>>>>
>>>>base64
>>>>
>>>>
>>>>------------------------------------------------------------------------
>>>>Part 1.3
>>>>
>>>>Content-Type:
>>>>
>>>>text/plain
>>>>Content-Encoding:
>>>>
>>>>binary
>>>>
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