Which APEX am I logging into?

I’ve got two computers at home both running APEX, and when I log into APEX the page looks exactly the same – except for the IP address in the URL, which is just slightly different. If you’re forgetful like me it’s easy to confuse which machine I’m logged in to. Here’s a tip:

Login to apex_admin on each machine in turn and click Manage Service, then Messages. Then select a Custom Message for the Login Message and/or a System Message, and enter the name of the machine, or some other message that will remind you which machine it is. The message will be shown whenever you see the login screen, and when you login to APEX.

If you find the text isn’t visible enough, you can insert HTML into the message, e.g. <B>Development</B>.


Un-riching Rich Text Format

Let’s just call it Legacy because I’m not going to say what the source is. It is a single-user desktop application that after a little investigation (i.e. searching the online forum for the app) was found to be storing its data in tables readable by MS Access. I wanted to get at this data, analyze it, maybe do some smart things to it, and then present it via Apex.

Step 1: Get the data into Oracle.

Simple matter of exporting from MS Access via ODBC. At least, it was simple once I replaced the Oracle ODBC drivers with the latest download from OTN. Before that I was getting a number of annoying TNS errors.

Step 2: Transform the data.

Most of the tables are easy-to-understand normalized relational tables. One of them, however, has a column that came through as a CLOB containing strange values like this:

{\rtf1\ansi\deff0\deftab254
{\fonttbl{\f0\fnil\fcharset0 Arial;}
{\f1\fnil\fcharset0 Verdana;}}{\colortbl\red0\green0\blue0;\red255\green0\blue0;\red0\green128\blue0;\red0\green0\blue255;\red255\green255\blue0;\red255\green0\blue255;\red128\green0\blue128;\red128\green0\blue0;\red0\green255\blue0;\red0\green255\blue255;\red0\green128\blue128;\red0\green0\blue128;\red255\green255\blue255;\red192\green192\blue192;\red128\green128\blue128;\red255\green255\blue255;}
\paperw12240\paperh15840\margl1880\margr1880\margt1440\margb1440
{\*\pnseclvl1\pnucrm\pnstart1\pnhang\pnindent720
{\pntxtb}{\pntxta{.}}}
...

Now based on my knowledge of the application I knew that this column was used to store small pieces of text (typically 8 to 30 short lines), with some amount of formatting (e.g. fonts, alignment, etc.). Again the online forum came in useful in that a side comment from one of the developers (regarding a small bug undocumented anti-feature) revealed that they stored the formatted text as RTF – Rich Text Format. Should have known from the opening 6 bytes in the data.

Somewhere in these oceans of rtf codes were swimming the plain text I craved. So Googled RTF, skimmed this old RTF specification, and ended up with this admittedly poorly-performing PL/SQL, which for the 651 rows in this table, each with an RTF of average 3KB, works just well enough for my purposes. As it turned out the only RTF codes I was interested in were \fcharset and \*, both of which I used to ignore bits of text I didn’t want in my output. Oh and \par, which denotes the end of a paragraph. I can run this script once a month on the freshly exported data and apply the full weight of Oracle’s analytic capabilities on it.

The code below exemplifies the use of a pipelined function. This is not a good idea, by the way, if you want to use it in regular queries, e.g. a view. In my case, however, I only wanted to call this from within PL/SQL, and then only once a month. Because of the way parameters work with functions like this, I had to call it with dynamic SQL (execute immediate).

That was kind of fun, but I’d rather not have to deal with RTF ever again, thank you.

create or replace package myutil_rtf is
  type t_v4000_table is table of varchar2(4000);
  function extract_text (p_recid in number)
  return t_v4000_table pipelined deterministic;
end;
/

create or replace package body myutil_rtf is
  function extract_text (p_recid in number)
    return t_v4000_table pipelined deterministic is

    l_ch varchar2(1);
    l_ctrl varchar2(4000);
    l_line varchar2(4000);
    l_rtf clob;

    --don't output any text between
    --\fcharset and closing }
    l_fcharset boolean := false;

    --increments for each enclosed pair of { }
    --within a discard section
    l_discard number;

  begin

    select rtf_clob into l_rtf
    from rtf_table where recid = p_recid;

    for i in 1..dbms_lob.getlength(l_rtf) loop

      l_ch := substr(l_rtf,i,1);

      if l_ch = '}' then

        if l_fcharset then
          --closing } found; re-enable output
          l_fcharset := false;
          l_line := null;
        end if;

        if l_discard > 0 then
          l_discard := l_discard - 1;
          if l_discard = 0 then
            l_discard := null;
          end if;
        end if;

      elsif l_ch = '{' then

        if l_discard is not null then
          l_discard := l_discard + 1;
        end if;

      elsif l_ch = '\' then

        --controls start with a backslash
        l_ctrl := '\';

      elsif l_ctrl is not null then

        --controls are always ended by some
        --non-alphanumeric character
        if instr('abcdefghijklmnopqrstuvwxyz'
        || '0123456789',lower(l_ch)) > 0 then
          l_ctrl := l_ctrl || lower(l_ch);
        else
          if l_ctrl = '\par' then
            pipe row (l_line);
            l_line := null;
          elsif substr(l_ctrl,1,9) = '\fcharset' then
            l_fcharset := true;
          elsif l_ctrl || l_ch = '\*' then
            --{\* ... } means you can ignore
            --anything between the { }
            if l_discard is null then
              l_discard := 1;
            end if;
          end if;
          l_ctrl := null;
        end if;

      elsif l_ch not in (chr(10), chr(13), '{')
        and not l_fcharset and l_discard is null then

        l_line := l_line || l_ch;

      end if;

    end loop;

    if l_line is not null and not l_fcharset then
      pipe row (l_line);
    end if;

    return;
  end extract_text;
end myutil_rtf;
/

To extract the text from the table with recid=1:

select column_value line_of_text
      ,rownum line_number
from table(myutil_rtf.extract_text(1));

Do you know the difference between USER_TAB_COLS & USER_TAB_COLUMNS?

I just noticed the difference – I was wondering why I couldn’t see the virtual columns (i.e. columns that support function-based indexes) on a table, and it was because I was querying USER_TAB_COLUMNS. Once I used USER_TAB_COLS instead there they were.

The difference is noted in the documentation (Oracle 10g Release 2 (10.2)) for USER_TAB_COLS and ALL_TAB_COLS but not for USER_TAB_COLUMNS or ALL_TAB_COLUMNS, unfortunately.


Replace the default XDB welcome page

I was annoyed that to get to my main PL/SQL page I have to type in a full URL like this:

http://host:7777/mydad/home

(e.g. “mydad” could be “apex” for Oracle Apex)

If I was using Apache HTTP Server I’d do something this article suggests. But I’m using Oracle’s Embedded PL/SQL Gateway.

A. I got rid of the “:7777” by changing the HTTP port to 80, e.g.:

SQL> exec dbms_xdb.sethttpport(80);

Now, I can get to it without the port number:

http://host/mydad/home

B. Now I want to remove the need to remember to type “home”. To do this, I just tell the DAD what the default page is:

SQL> exec dbms_epg.set_dad_attribute('MYDAD','default-page','home');

Now, the url is a bit simpler:

http://host/mydad

The URL is now rewritten automatically to point to “mydad/home”.

C. Finally, I want to remove the need to specify the DAD. To do this is a little more complicated. I’ll create an XDB resource that will override the default XDB navigator that comes up.

    1. Log into Enterprise Manager

 

    1. Open the “Administration” tab and select “Resources” under “XML Database”

 

    1. Click “Create” and set the fields as follows:
      Owner = SYS
      Name = index.html
      Location = /
      Type = XML Database Resource File
      Source = Specify the file contents
      Contents =
      <html><head><meta http-equiv="REFRESH" content="0; URL=http://host/mydad"></head><body><a href="http://host/mydad">Home</a></body></html>

 

  1. Click “Ok”

(you’ll need to change “host” and “mydad” to appropriate values in the sample Contents above)

Now, the url is simply:

http://host

This causes it to load the index.html page from the XML database, which redirects to the DAD, the default page for which is “home”.


APEX 3.0 via Embedded PL/SQL Gateway

I managed to get APEX 3.0 working on Oracle 10.2.0.1 using the embedded PL/SQL gateway (i.e. without installing Apache), contrary to the advice given here. I used apex_epg_config instead of apex_epg_config11. For it to work, however, I had to remove some security on XDB so it’s not a recommended option. This involved modifying my xdbconfig.xml to allow anonymous access to XDB using this:

DECLARE
  configxml SYS.XMLType;
BEGIN
  SELECT INSERTCHILDXML(xdburitype('/xdbconfig.xml').getXML(),
         '/xdbconfig/sysconfig/protocolconfig/httpconfig',
         'allow-repository-anonymous-access',
         XMLType('true'),
         'xmlns=&quot;http://xmlns.oracle.com/xdb/xdbconfig.xsd&quot;')
  INTO configxml FROM DUAL;
  DBMS_XDB.cfg_update(configxml);
END;
/

Now for some general tips:

Tip #1. List Your DAD Authorizations

As described so well in the excellent article DBMS_EPG – The Embedded PL/SQL Gateway in Oracle 10g Database Release 2, you can authorize and deauthorize a DAD using the DBMS_EPG package. It should be noted that dropping a DAD will not remove the authorizations as well, so you need to deauthorize it as well. To find out what authorizations have been made on your database, you can query the DBA_EPG_DAD_AUTHORIZATION view, e.g.:

SQL&gt; select * from dba_epg_dad_authorization;

DAD_NAME USERNAME
-------- ---------
APEX     ANONYMOUS

1 row selected.

There’s also a USER_EPG_DAD_AUTHORIZATION view which shows the DAD_NAME for authorized DADs for the current user.


Tip #2. List Your DADS

You can find out what DADs have been set up on your instance using the DBMS_EPG package. There is a bug, however, that causes dbms_epg.get_all_dad_attributes to return nothing, so this script gets each attribute separately with dbms_epg.get_dad_attribute. The script lists all the DADS, their mappings and their attributes.

set serveroutput on

PROMPT list all dads
declare
  blank       dbms_epg.varchar2_table;
  dad_names   dbms_epg.varchar2_table;
  paths       dbms_epg.varchar2_table;
  procedure show_dad_attribute(dad in varchar2, attr in varchar2) is
    val varchar2(4000);
  begin
    val := dbms_epg.get_dad_attribute(dad, attr);
    if val is not null then
      dbms_output.put_line('... ' || attr || '=' || val);
    end if;
  end;
begin
  dbms_epg.get_dad_list(dad_names);
  if dad_names.count &gt; 0 then
    for i in dad_names.first..dad_names.last loop
      dbms_output.put_line(dad_names(i));
      paths := blank;
      dbms_epg.get_all_dad_mappings(dad_names(i), paths);
      if paths.count &gt; 0 then
        for j in paths.first..paths.last loop
          dbms_output.put_line('... path=' || paths(j));
        end loop;
      else
        dbms_output.put_line('... No mappings found');
      end if;
      show_dad_attribute(dad_names(i),'after-procedure');
      show_dad_attribute(dad_names(i),'always-describe-procedure');
      show_dad_attribute(dad_names(i),'authentication-mode');
      show_dad_attribute(dad_names(i),'before-procedure');
      show_dad_attribute(dad_names(i),'bind-bucket-lengths');
      show_dad_attribute(dad_names(i),'bind-bucket-widths');
      show_dad_attribute(dad_names(i),'cgi-environment-list');
      show_dad_attribute(dad_names(i),'compatibility-mode');
      show_dad_attribute(dad_names(i),'database-username');
      show_dad_attribute(dad_names(i),'default-page');
      show_dad_attribute(dad_names(i),'document-path');
      show_dad_attribute(dad_names(i),'document-procedure');
      show_dad_attribute(dad_names(i),'document-table-name');
      show_dad_attribute(dad_names(i),'error-style');
      show_dad_attribute(dad_names(i),'exclusion-list');
      show_dad_attribute(dad_names(i),'fetch-buffer-size');
      show_dad_attribute(dad_names(i),'input-filter-enable');
      show_dad_attribute(dad_names(i),'info-logging');
      show_dad_attribute(dad_names(i),'owa-debug-enable');
      show_dad_attribute(dad_names(i),'max-requests-per-session');
      show_dad_attribute(dad_names(i),'nls-language');
      show_dad_attribute(dad_names(i),'path-alias');
      show_dad_attribute(dad_names(i),'path-alias-procedure');
      show_dad_attribute(dad_names(i),'request-validation-function');
      show_dad_attribute(dad_names(i),'session-cookie-name');
      show_dad_attribute(dad_names(i),'session-state-management');
      show_dad_attribute(dad_names(i),'transfer-mode');
      show_dad_attribute(dad_names(i),'upload-as-long-raw');
    end loop;
  else
    dbms_output.put_line('No dads found');
  end if;
end;
/

When the above script is run, you’ll get something like this:

APEX
... path=/apex/*
... authentication-mode=Basic
... database-username=ANONYMOUS
... default-page=apex
... document-path=docs
... document-procedure=wwv_flow_file_mgr.process_download
... document-table-name=wwv_flow_file_objects$
... nls-language=american_america.al32utf8
... request-validation-function=wwv_flow_epg_include_modules.authorize

ZFS/Oracle

Zettabyte File System (APC)

Pooled storage, transactional control, snapshots… sounds awfully familiar to me. Oh yeah, features that Oracle have provided in the database for years. 🙂

(I know, very different domain and probably very different implementation (database vs. file system) but some of the concepts are similar.)


ORA-06502: PL/SQL: numeric or value error: Bulk bind: Error in define

I came across an inexplicable error when bulk collecting into a PL/SQL table with the NOT NULL constraint the other day. What was confusing was that the code had been passing tests for quite some time.

In the end the only thing that had changed was that a VARCHAR2 which should have been non-null happened to be NULL for one particular row in the table.

Thanks to Connor for the simple test case, listed below.

If you know what might be the cause or reason behind this error, and why it doesn’t occur for dates, I’d be interested.

This was reproduced on Oracle 10.2.0.1.0.

SQL> declare
      type t is table of number not null index by pls_integer;
      r t;
     begin
      select case when rownum < 20 then rownum else null end
      bulk collect into r from all_Objects
      where rownum <= 20;
     end;
     /
declare
*
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: Bulk bind: Error in define
ORA-06512: at line 5

SQL> declare
      type t is table of varchar2(80) not null index by pls_integer;
      r t;
     begin
      select case when rownum < 20 then rownum else null end
      bulk collect into r from all_Objects
      where rownum <= 20;
     end;
     /
declare
*
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: Bulk bind: Error in define
ORA-06512: at line 5

SQL> declare
      type t is table of date not null index by pls_integer;
      r t;
     begin
      select case when rownum < 20 then sysdate else null end
      bulk collect into r from all_Objects
      where rownum <= 20;
     end;
     /
PL/SQL procedure successfully completed.

Table Types Supplied by Oracle

This is a list of all the table types I’ve found in Oracle-supplied packages, e.g. OWA_UTIL in 10g supplies the type:
TYPE datetype IS TABLE OF varchar2(10) INDEX BY binary_integer;

I find them handy for quick one-off scripts.

Oracle_supplied_table_types


Generic Audit

Looking at the column comments on this table, I can sympathise with the poor soul who after painstakingly describing 100 columns just decided that it just wasn’t worth it…

table audit_history (column comments in quotes):

id number(18) “Unique identifier”
aud_table_name varchar2(30) “audit record table”
audit_action varchar2(50) “audit action e.g. update”
aud_timestamp date “timestamp of the audit”
aud_user_id varchar2(100) “user performing the action”
aud_col_1 varchar2(4000) “audit column 1”
aud_col_2 varchar2(4000) “audit column 2”
aud_col_3 varchar2(4000) “audit column 3”
… (etc.) …
aud_col_99 varchar2(4000) “audit column 99”
aud_col_100 varchar2(4000) “audit column 100”
aud_col_101 varchar2(4000)
aud_col_102 varchar2(4000)
… (etc.) …
aud_col_139 varchar2(4000)
aud_col_140 varchar2(4000)

Tip: Don’t let anyone even think about using this kind of design for their change history auditing requirements. It might look elegant to them, but it is not good. Just, don’t.


SQL Developer Wish List

I’m starting to come around to Oracle SQL Developer. At home I only use free software so that’s obviously a big plus, but at work I’m still using PL/SQL Developer (Allround Automations) and SQL*Plus.

These are the features I like best about these products:

SQL Developer:

  • Connection management
    • Connection browser
    • Multiple simultaneous connections
    • Password persistance
    • Quick connection switching within SQL worksheet
  • Object viewer
    • Easy Query management
    • Nicer plan viewer

PL/SQL Developer:

  • Faster startup, smaller memory footprint
  • Fully configurable object browser
    • Re-order categories
    • Create/modify/delete categories
    • Colour coding
  • Data browser
    • Edit data directly in grid
    • View data, including LOBs, e.g. RTF, XML, HTML, hex, etc.
  • Window management
    • Summary tab lists all windows, indicating which are unsaved or are currently running SQL
  • Query management
    • Runs DDL and DML in a second session, easy to cancel queries
  • Smart SQL and PL/SQL Editing
    • Context-sensitive menus
    • Smarter, context-sensitive code suggestions
    • Configurable SQL beautifier
  • Session browser, configurable

I’d like to see Oracle work on some of these features before I switch over at work. I’d also like to see SQL Developer able to export LOBs when exporting tables to XML.