PL/SQL Limit When Dealing with a CLOB?

Question

Greetings,
I am constructing HTML into a CLOB in a PL/SQL routine which I later display in an APEX application. The HTML can get large, because I am constructing a grid over an image, and the grid can have a lot of columns and rows which means there can be a lot of <area shape="rect" HTML lines. I did a search and found that another person had the same problem, because there is a 32K limit with HTML contents. That was very helpful.
Thing is - I have another (maybe similar) issue. The procedure that constructs the HTML gets a numeric error when the number of cells in the grid reach a certain point. I checked and this happens when the CLOB in the procedure gets close to 32K. Sorry, it difficult to know exactly when it fails, but the most I have been able to put into the CLOB is 32,852 characters. Therefore my question - is there in internal limit in PL/SQL (or some other Oracle aspect) that is limited to 32K? The coluimn in the table that contains the HTML is a CLOB and the variable in the PL/SQL that the HTML is parsed into is a CLOB, so I thought I was good to go since the CLOB limit is 4GB. But, it looks like I may be missing something.
We are running Oracle 11i and APEX 4.0.2.00.07. If other system info is needed let me know and I will get that for you.
Also, if it helps. The code from the procedure is copied below. v_html is the variable that holds the HTML. The table column for the HTML is imagemap_html. Both v_html and imagemap_html are defined as CLOB's.
Thanks, Tony
= = = = = = =
create or replace
procedure create_grid (p_action IN VARCHAR2) as
    v_wcount integer := 0;   
    v_wmax integer := 20;
    v_width integer := 720;
    v_w1 integer := 0;
    v_w2 integer := 0;
    v_winc integer := 0;
    v_wstart integer := 0;
    v_wend integer := 0;   
    v_hcount integer := 0;
    v_hmax integer := 10;
    v_height integer := 520;
    v_h1 integer := 0;
    v_h2 integer := 0;
    v_hinc integer := 0;
    v_hstart integer := 0;
    v_hend integer := 0;   
    v_cell_row integer := 0;
    v_cell_col integer := 0;
    v_cell_title varchar2(10) := NULL;
    v_whitespace varchar2(10) := NULL;
    v_url_1 varchar2(100) := NULL;
    v_url_2 varchar2(100) := NULL;
    v_url_3 varchar2(100) := NULL;
    v_brand_id integer := 0;
    v_division_id integer := 0;
    v_plant_id integer := 0;
    v_model_id integer := 0;
    v_acc_group integer := 0;
    v_accessory integer := 0;
    v_acc_grp integer := 0;
    v_acc integer := 0;
    v_station_id integer := 0;
    v_substation_id integer := 0;     
    v_image_id integer := 0;
    v_id integer := 0;  
    v_html clob;
  begin
  v_brand_id := v('P4_BRAND_ID');
  v_division_id :=v('P4_DIVISION_ID');
  v_plant_id := v('P4_PLANT_ID');
  v_model_id := v('P4_MODEL_ID');
  v_acc_group := v('P4_ACC_GROUP');
  v_accessory := v('P4_ACCESSORY');
  v_station_id := v('P4_STATION_ID');
  v_substation_id := v('P4_SUBSTATION_ID');
  v_image_id := v('P4_IMAGES_ID');
  v_wmax := v('P4_COLUMNS');
  v_hmax := v('P4_ROWS');
  v_wstart := v('P4_XSTART');
  v_hstart := v('P4_YSTART');
  v_wend := v('P4_XEND');
  v_hend := v('P4_YEND'); 
  v_whitespace := v('P4_WHITESPACE');
if p_action = 'INSERT' then
-- insert the row now, so that the cell table rows can be inserted with the correct FK 
insert into IM_TEMPLATE_DRAFT
(plant_id, brand_id, division_id, model_id, acc_group, accessory, station_id,
substation_id, image_id)
values
(v_plant_id,v_brand_id,v_division_id,v_model_id,v_acc_group,v_accessory,v_station_id,v_substation_id,v_image_id);
commit;
end if;
-- get the id of the row that was just inserted
select header_id into v_id from  IM_TEMPLATE_DRAFT where
plant_id=v_plant_id and brand_id=v_brand_id and division_id=v_division_id and
model_id=v_model_id and acc_group=v_acc_group and accessory=v_accessory and
station_id=v_station_id and substation_id=v_substation_id and image_id=v_image_id;
-- remove all the cell rows for the draft, they will be created anew
delete from qcis_draft_cells where draft_id = v_id;
  BEGIN
  select pixel_width, pixel_height into v_width, v_height from images
  where images_id = v_image_id;
  EXCEPTION
    WHEN NO_DATA_FOUND THEN
    v_height := 720;
    v_width := 520;
  END;
-- the first part of the href for the image is stored in the keyword table and put into v_url_1 for use later
  BEGIN
  select keyword_value into v_url_1 from qcis_keywords
  where keyword_type = 'Control' and keyword_code = 'URL_PATH';
  EXCEPTION
    WHEN NO_DATA_FOUND THEN
    v_url_1 := 'http://xxx.xxx.com:8000/apex40/f?p=';
  END; 
-- construct the first three lines of the div tag 
  v_html := '<div style="text-align:center; width:'||v_width||'px; margin-left:auto; margin-right:auto;">';
  v_html := v_html || chr(10) || '<img id="ImageMap" src="download_image?p_id='||v_image_id||'" usemap="#ImageMap" border="0" width="'||v_width||'" height="'||v_height||'" alt="" />';
  v_html := v_html || chr(10) || '<map id="_ImageMap" name="ImageMap">';
-- subtract the ending inset amounts from the image dimensions
  v_width := v_width - v_wend;
  v_height := v_height - v_hend;
-- calculate the increment for each cell and subtract the starting inset amounts
  v_winc := floor((v_width - v_wstart) / v_wmax);
  v_hinc := floor((v_height - v_hstart) / v_hmax);
-- there are two main loops, one for the columns, one for the rows
-- one loop is inside the other, which helps to build the cells in logical order and helps with the naming of the cells 
  loop
-- if this is the first row (count = 0) and they have inset values we need to adust the first x y values to something other than zero 
if ((v_wstart != 0) and (v_wcount = 0)) then v_w1 := v_wstart; end if;
if ((v_hstart != 0) and (v_hcount = 0)) then v_h1 := v_hstart; end if;
if ((v_wstart != 0) and (v_wcount = 0)) then v_w2 := v_wstart; end if;
if ((v_hstart != 0) and (v_hcount = 0)) then v_h2 := v_hstart; end if;
v_wcount := v_wcount + 1;
v_w2 := v_w2 + v_winc;
-- checking to see if this is the last row and whether they want the grid to go to the end or have all cells the same size which may leave whitespace
         if (v_wcount = v_wmax) and (v_whitespace = 'Y') then v_w2 := v_width - 2; end if;
  v_cell_row := 0;
  v_cell_col := v_cell_col +1;
         loop
         v_hcount := v_hcount + 1;           
         v_h2 := v_h2 + v_hinc;
-- checking to see if this is the last row and whether they want the grid to go to the end or have all cells the same size which may leave whitespace
                if (v_hcount = v_hmax) and (v_whitespace = 'Y') then v_h2 := v_height - 2; end if;
         v_cell_row := v_cell_row + 1;
         -- put it all together and construct the line for the area shape tag
         v_html := v_html || chr(10) || '<area shape="rect" coords="'
         ||v_w1||','||v_h1||','||v_w2||','||v_h2||
         '" href="'||v_url_1|| '" alt="'||v_cell_col||'-'||v_cell_row||'" title="'||v_cell_col||'-'||v_cell_row||'"    />';
         v_cell_title := v_cell_col||'-'||v_cell_row;
            insert into DRAFT_CELLS (DRAFT_ID, CELL_TITLE) values(v_id, v_cell_title);          
         v_h1 := v_h1 + v_hinc;
            exit when v_hcount = v_hmax;
        end loop;
  v_hcount := 0;
  v_h1 := 0;
  v_h2 := 0;
  v_w1 := v_w1 + v_winc;
     exit when v_wcount = v_wmax;     
  end loop;
  v_html := v_html || chr(10) || '</div>';
update IM_TEMPLATE_DRAFT set imagemap_html = v_html
where header_id = v_id;  
END create_grid;Edited by: cloaked on Nov 7, 2011 4:45 AM

Answer 1

For "Application Express 4.2.1.00.08" i created such good solution.
I downloaded freeware plugin "Enkitec Clob Load Plug-in Version: 1.0.0 - APEX Version: 4.2.0" from there:
http://www.enkitec.com/products/plugins/clob-load/help
Then i followed plugin installation steps and created a APEX page where i added an item of type "Rich Text Editor".
I found the plugin crashes when my database CLOB field is empty, also crashed when i tried to save down empty value to database.
I changed Plugin code a little, and now everything works as needed, i can save down larga data, and also empty data.
1. In Apex open plugin "Enkitec CLOB Load".
2. Navigate to "Source-->PL/SQL Code" where is text area with plugin source code.
3. there you have such code:
FUNCTION enkitec_clob_load_render (
   p_dynamic_action IN APEX_PLUGIN.T_DYNAMIC_ACTION,
   p_plugin         IN APEX_PLUGIN.T_PLUGIN
   RETURN APEX_PLUGIN.T_DYNAMIC_ACTION_RENDER_RESULT
IS
   l_retval           APEX_PLUGIN.T_DYNAMIC_ACTION_RENDER_RESULT;
   l_show_modal       VARCHAR2(1) := p_plugin.attribute_01;
   l_dialog_title     VARCHAR2(4000) := NVL(p_plugin.attribute_02, 'Please wait...');
   l_loading_img_type VARCHAR2(30) := p_plugin.attribute_03;
   l_loading_img_c    VARCHAR2(4000) := p_plugin.attribute_04;
   l_action           VARCHAR2(10) := NVL(p_dynamic_action.attribute_01, 'RENDER');
   l_change_only      VARCHAR2(1) := NVL(p_dynamic_action.attribute_06, 'Y');
   l_make_blocking    VARCHAR2(1) := NVL(p_dynamic_action.attribute_07, 'Y');
   l_loading_img_src  VARCHAR2(32767);
   l_crlf             VARCHAR2(2) := CHR(13)||CHR(10);
   l_js_function      VARCHAR2(32767);
   l_onload_code      VARCHAR2(32767);
BEGIN
   IF apex_application.g_debug
   THEN
      apex_plugin_util.debug_dynamic_action(
         p_plugin         => p_plugin,
         p_dynamic_action => p_dynamic_action
   END IF;
   IF l_loading_img_type = 'DEFAULT'
   THEN
      l_loading_img_src := p_plugin.file_prefix || 'enkitec-loading.gif';
   ELSE
      l_loading_img_src := REPLACE(l_loading_img_c, '#IMAGE_PREFIX#', apex_application.g_image_prefix);
      l_loading_img_src := REPLACE(l_loading_img_src, '#PLUGIN_PREFIX#', p_plugin.file_prefix);
   END IF;
   apex_css.add(
      p_css => '.clob-load-dialog .ui-dialog-titlebar-close {display: none;}',
      p_key => 'clob-load-hide-modal-close'
   apex_javascript.add_library(
      p_name      => 'enkitec-clob-load.min',
      p_directory => p_plugin.file_prefix,
      p_version   => NULL
   l_onload_code :=
      'apex.jQuery(document).clob_load({'|| l_crlf ||
      '   showModal: "' || l_show_modal ||'",'|| l_crlf ||
      '   dialogTitle: "' || l_dialog_title ||'",'|| l_crlf ||
      '   loadingImageSrc: "' || l_loading_img_src ||'",'|| l_crlf ||
      '   pluginFilePrefix: "' || p_plugin.file_prefix || '",' || l_crlf ||
      '   apexImagePrefix: "' || apex_application.g_image_prefix || ',"' || l_crlf ||
   apex_javascript.add_onload_code(
      p_code => l_onload_code
   IF l_action = 'RENDER'
   THEN
      l_js_function :=
         'function(){'|| l_crlf ||
         '   apex.jQuery(document).clob_load("renderClob", {' || l_crlf ||
         '      $elmt: this.affectedElements.eq(0),' || l_crlf ||
         '      ajaxIdentifier: "' || apex_plugin.get_ajax_identifier() || '"' || l_crlf ||
         '   });'|| l_crlf ||
   ELSE
      l_js_function :=
         'function(){'|| l_crlf ||
         '   apex.jQuery(document).clob_load("submitClob", {' || l_crlf ||
         '      $elmt: this.affectedElements.eq(0),' || l_crlf ||
         '      ajaxIdentifier: "' || apex_plugin.get_ajax_identifier() || '",' || l_crlf ||
         '      changeOnly: "' || l_change_only || '",' || l_crlf ||
         '      makeBlocking: "' || l_make_blocking || '"' || l_crlf ||
         '   });'|| l_crlf ||
   END IF;
   l_retval.javascript_function := l_js_function;
   RETURN l_retval;
END enkitec_clob_load_render;
FUNCTION enkitec_clob_load_ajax (
   p_dynamic_action IN APEX_PLUGIN.T_DYNAMIC_ACTION,
   p_plugin         IN APEX_PLUGIN.T_PLUGIN
    RETURN APEX_PLUGIN.T_DYNAMIC_ACTION_AJAX_RESULT
IS
   l_retval                   APEX_PLUGIN.T_DYNAMIC_ACTION_AJAX_RESULT;
   l_ajax_function            VARCHAR2(32767) := apex_application.g_x01;
   l_source                   VARCHAR2(20) := NVL(p_dynamic_action.attribute_02, 'COLLECTION');
   l_render_collection_name   VARCHAR2(255) := p_dynamic_action.attribute_03;
   l_query                    VARCHAR2(32767) := p_dynamic_action.attribute_04;
   l_submit_collection_name   VARCHAR2(255) := p_dynamic_action.attribute_05;
   l_column_value_list        APEX_PLUGIN_UTIL.T_COLUMN_VALUE_LIST2;    
   l_clob_text                CLOB := EMPTY_CLOB();
   l_token                    VARCHAR2(32000);
   l_chunk_size               NUMBER := 4000;
BEGIN
   IF l_ajax_function = 'RENDER_CLOB'
   THEN
      IF l_source = 'COLLECTION'
      THEN
         IF apex_collection.collection_exists(l_render_collection_name)
         THEN
            SELECT clob001
            INTO l_clob_text
            FROM apex_collections
            WHERE collection_name = l_render_collection_name
               AND seq_id = 1;
         END IF;
      ELSE --must be SQL_QUERY
         BEGIN
            l_column_value_list := apex_plugin_util.get_data2(
               p_sql_statement  => l_query,
               p_min_columns    => 1,
               p_max_columns    => 1,
               p_component_name => p_dynamic_action.action,
               p_first_row      => 1,
               p_max_rows       => 1
         EXCEPTION
            WHEN NO_DATA_FOUND
            THEN
               NULL;
         END;
         IF l_column_value_list.exists(1)
            AND l_column_value_list(1).value_list.exists(1)
         THEN
            l_clob_text := l_column_value_list(1).value_list(1).clob_value;
         END IF;
      END IF;
      FOR i IN 0 .. FLOOR(LENGTH(l_clob_text)/l_chunk_size)
      LOOP 
         sys.htp.prn(substr(l_clob_text, i * l_chunk_size + 1, l_chunk_size)); 
      END LOOP;
   ELSE --must be SUBMIT_CLOB
      dbms_lob.createtemporary(l_clob_text, false, dbms_lob.session);
      FOR i IN 1..apex_application.g_f01.count
      LOOP
         l_token := wwv_flow.g_f01(i);
         dbms_lob.writeappend(l_clob_text, length(l_token), l_token);
      END LOOP;
      apex_collection.create_or_truncate_collection(
         p_collection_name => l_submit_collection_name
      apex_collection.add_member(
         p_collection_name => l_submit_collection_name,
         p_clob001         => l_clob_text
   END IF;
   RETURN l_retval;
END enkitec_clob_load_ajax;4. Change this code to this code:
FUNCTION enkitec_clob_load_render (
   p_dynamic_action IN APEX_PLUGIN.T_DYNAMIC_ACTION,
   p_plugin         IN APEX_PLUGIN.T_PLUGIN
   RETURN APEX_PLUGIN.T_DYNAMIC_ACTION_RENDER_RESULT
IS
   l_retval           APEX_PLUGIN.T_DYNAMIC_ACTION_RENDER_RESULT;
   l_show_modal       VARCHAR2(1) := p_plugin.attribute_01;
   l_dialog_title     VARCHAR2(4000) := NVL(p_plugin.attribute_02, 'Please wait...');
   l_loading_img_type VARCHAR2(30) := p_plugin.attribute_03;
   l_loading_img_c    VARCHAR2(4000) := p_plugin.attribute_04;
   l_action           VARCHAR2(10) := NVL(p_dynamic_action.attribute_01, 'RENDER');
   l_change_only      VARCHAR2(1) := NVL(p_dynamic_action.attribute_06, 'Y');
   l_make_blocking    VARCHAR2(1) := NVL(p_dynamic_action.attribute_07, 'Y');
   l_loading_img_src  VARCHAR2(32767);
   l_crlf             VARCHAR2(2) := CHR(13)||CHR(10);
   l_js_function      VARCHAR2(32767);
   l_onload_code      VARCHAR2(32767);
BEGIN
   IF apex_application.g_debug
   THEN
      apex_plugin_util.debug_dynamic_action(
         p_plugin         => p_plugin,
         p_dynamic_action => p_dynamic_action
   END IF;
   IF l_loading_img_type = 'DEFAULT'
   THEN
      l_loading_img_src := p_plugin.file_prefix || 'enkitec-loading.gif';
   ELSE
      l_loading_img_src := REPLACE(l_loading_img_c, '#IMAGE_PREFIX#', apex_application.g_image_prefix);
      l_loading_img_src := REPLACE(l_loading_img_src, '#PLUGIN_PREFIX#', p_plugin.file_prefix);
   END IF;
   apex_css.add(
      p_css => '.clob-load-dialog .ui-dialog-titlebar-close {display: none;}',
      p_key => 'clob-load-hide-modal-close'
   apex_javascript.add_library(
      p_name      => 'enkitec-clob-load.min',
      p_directory => p_plugin.file_prefix,
      p_version   => NULL
   l_onload_code :=
      'apex.jQuery(document).clob_load({'|| l_crlf ||
      '   showModal: "' || l_show_modal ||'",'|| l_crlf ||
      '   dialogTitle: "' || l_dialog_title ||'",'|| l_crlf ||
      '   loadingImageSrc: "' || l_loading_img_src ||'",'|| l_crlf ||
      '   pluginFilePrefix: "' || p_plugin.file_prefix || '",' || l_crlf ||
      '   apexImagePrefix: "' || apex_application.g_image_prefix || ',"' || l_crlf ||
   apex_javascript.add_onload_code(
      p_code => l_onload_code
   IF l_action = 'RENDER'
   THEN
      l_js_function :=
         'function(){'|| l_crlf ||
         '   apex.jQuery(document).clob_load("renderClob", {' || l_crlf ||
         '      $elmt: this.affectedElements.eq(0),' || l_crlf ||
         '      ajaxIdentifier: "' || apex_plugin.get_ajax_identifier() || '"' || l_crlf ||
         '   });'|| l_crlf ||
   ELSE
      l_js_function :=
         'function(){'|| l_crlf ||
         '   apex.jQuery(document).clob_load("submitClob", {' || l_crlf ||
         '      $elmt: this.affectedElements.eq(0),' || l_crlf ||
         '      ajaxIdentifier: "' || apex_plugin.get_ajax_identifier() || '",' || l_crlf ||
         '      changeOnly: "' || l_change_only || '",' || l_crlf ||
         '      makeBlocking: "' || l_make_blocking || '"' || l_crlf ||
         '   });'|| l_crlf ||
   END IF;
   l_retval.javascript_function := l_js_function;
   RETURN l_retval;
END enkitec_clob_load_render;
FUNCTION enkitec_clob_load_ajax (
   p_dynamic_action IN APEX_PLUGIN.T_DYNAMIC_ACTION,
   p_plugin         IN APEX_PLUGIN.T_PLUGIN
    RETURN APEX_PLUGIN.T_DYNAMIC_ACTION_AJAX_RESULT
IS
   l_retval                   APEX_PLUGIN.T_DYNAMIC_ACTION_AJAX_RESULT;
   l_ajax_function            VARCHAR2(32767) := apex_application.g_x01;
   l_source                   VARCHAR2(20) := NVL(p_dynamic_action.attribute_02, 'COLLECTION');
   l_render_collection_name   VARCHAR2(255) := p_dynamic_action.attribute_03;
   l_query                    VARCHAR2(32767) := p_dynamic_action.attribute_04;
   l_submit_collection_name   VARCHAR2(255) := p_dynamic_action.attribute_05;
   l_column_value_list        APEX_PLUGIN_UTIL.T_COLUMN_VALUE_LIST2;    
   l_clob_text                CLOB := EMPTY_CLOB();
   l_token                    VARCHAR2(32000);
   l_chunk_size               NUMBER := 4000;
BEGIN
   IF l_ajax_function = 'RENDER_CLOB'
   THEN
      IF l_source = 'COLLECTION'
      THEN
         IF apex_collection.collection_exists(l_render_collection_name)
         THEN
            SELECT clob001
            INTO l_clob_text
            FROM apex_collections
            WHERE collection_name = l_render_collection_name
               AND seq_id = 1;
         END IF;
      ELSE --must be SQL_QUERY
         BEGIN
            l_column_value_list := apex_plugin_util.get_data2(
               p_sql_statement  => l_query,
               p_min_columns    => 1,
               p_max_columns    => 1,
               p_component_name => p_dynamic_action.action,
               p_first_row      => 1,
               p_max_rows       => 1
         EXCEPTION
            WHEN NO_DATA_FOUND
            THEN
               NULL;
         END;
         IF l_column_value_list.exists(1)
            AND l_column_value_list(1).value_list.exists(1)
         THEN
            l_clob_text := l_column_value_list(1).value_list(1).clob_value;
         END IF;
      END IF;
      FOR i IN 0 .. FLOOR(NVL(LENGTH(l_clob_text)/l_chunk_size,0))
      LOOP 
         sys.htp.prn(substr(l_clob_text, i * l_chunk_size + 1, l_chunk_size)); 
      END LOOP;
   ELSE --must be SUBMIT_CLOB
      dbms_lob.createtemporary(l_clob_text, false, dbms_lob.session);
      FOR i IN 1..apex_application.g_f01.count
      LOOP
         l_token := wwv_flow.g_f01(i);
         if NVL(length(l_token),0) > 0 Then
            dbms_lob.writeappend(l_clob_text, length(l_token), l_token);
         end if;
      END LOOP;
      apex_collection.create_or_truncate_collection(
         p_collection_name => l_submit_collection_name
      apex_collection.add_member(
         p_collection_name => l_submit_collection_name,
         p_clob001         => l_clob_text
   END IF;
   RETURN l_retval;
END enkitec_clob_load_ajax;5. As you see only 2 places of plugin had to be fixed, when you compare previous 2 steps:
FOR i IN 0 .. FLOOR(LENGTH(l_clob_text)/l_chunk_size)
      LOOP 
         sys.htp.prn(substr(l_clob_text, i * l_chunk_size + 1, l_chunk_size)); 
      END LOOP;-->
FOR i IN 0 .. FLOOR(NVL(LENGTH(l_clob_text)/l_chunk_size,0))
      LOOP 
         sys.htp.prn(substr(l_clob_text, i * l_chunk_size + 1, l_chunk_size)); 
      END LOOP;And
FOR i IN 1..apex_application.g_f01.count
      LOOP
         l_token := wwv_flow.g_f01(i);
         dbms_lob.writeappend(l_clob_text, length(l_token), l_token);
      END LOOP;-->
FOR i IN 1..apex_application.g_f01.count
      LOOP
         l_token := wwv_flow.g_f01(i);
         if NVL(length(l_token),0) > 0 Then
            dbms_lob.writeappend(l_clob_text, length(l_token), l_token);
         end if;
      END LOOP;This way seems to be best way to handle APEX CLOBS today, using that plugin, and a little fix.