How to call REPLACE with CLOB (without exceeding 32K) - oracle

Question

Oracle 11g has certainly improved usability of CLOBs, having overloaded most of the string functions so they now work natively with CLOBs.
However, a colleague was getting this error from his code:
ORA-22828: input pattern or replacement parameters exceed 32K size limit
22828. 00000 - "input pattern or replacement parameters exceed 32K size limit"
*Cause: Value provided for the pattern or replacement string in the form of
VARCHAR2 or CLOB for LOB SQL functions exceeded the 32K size limit.
*Action: Use a shorter pattern or process a long pattern string in multiple
passes.
This only occurred when the third parameter to replace was a CLOB with more than 32k characters.
(Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production)
Test case:
declare
v2 varchar2(32767);
cl_small clob;
cl_big clob;
cl_big2 clob;
begin
v2 := rpad('x', 32767, 'x');
dbms_output.put_line('v2:' || length(v2));
cl_small := v2;
dbms_output.put_line('cl_small:' || length(cl_small));
cl_big := v2 || 'y' || v2;
dbms_output.put_line('cl_big[1]:' || length(cl_big));
cl_big2 := replace(cl_big, 'y', cl_small);
dbms_output.put_line('cl_big[2]:' || length(cl_big2));
cl_big2 := replace(cl_big, 'y', cl_big);
dbms_output.put_line('cl_big[3]:' || length(cl_big2));
end;
/
Results:
v2:32767
cl_small:32767
cl_big[1]:65535
cl_big[2]:98301
ORA-22828: input pattern or replacement parameters exceed 32K size limit
This seems at odds with the docs which imply that the replacement string may be a CLOB - I would have thought this should imply that any CLOB would be allowed, not just those that happen to be <32K: http://docs.oracle.com/cd/E11882_01/server.112/e41084/functions153.htm#SQLRF00697

Answer 1

Here is a rough first draft for a function that will do the job with certain limitations, it hasn't been very well tested yet:
function replace_with_clob
(i_source in clob
,i_search in varchar2
,i_replace in clob
) return clob is
l_pos pls_integer;
begin
l_pos := instr(i_source, i_search);
if l_pos > 0 then
return substr(i_source, 1, l_pos-1)
|| i_replace
|| substr(i_source, l_pos+length(i_search));
end if;
return i_source;
end replace_with_clob;
It only does a single replace on the first instance of the search term.
declare
v2 varchar2(32767);
cl_small clob;
cl_big clob;
cl_big2 clob;
begin
v2 := rpad('x', 32767, 'x');
dbms_output.put_line('v2:' || length(v2));
cl_small := v2;
dbms_output.put_line('cl_small:' || length(cl_small));
cl_big := v2 || 'y' || v2;
dbms_output.put_line('cl_big[1]:' || length(cl_big));
cl_big2 := replace(cl_big, 'y', cl_small);
dbms_output.put_line('cl_big[2]:' || length(cl_big2));
cl_big2 := replace_with_clob(cl_big, 'y', cl_big);
dbms_output.put_line('cl_big[3]:' || length(cl_big2));
end;
/
v2:32767
cl_small:32767
cl_big[1]:65535
cl_big[2]:98301
cl_big[3]:131069

Answer 2

You can create a function to handle CLOB values of any length:
SQL Fiddle
CREATE FUNCTION lob_replace(
i_lob IN clob,
i_what IN varchar2,
i_with IN clob,
i_offset IN INTEGER DEFAULT 1,
i_nth IN INTEGER DEFAULT 1
) RETURN CLOB
AS
o_lob CLOB;
n PLS_INTEGER;
l_lob PLS_INTEGER;
l_what PLS_INTEGER;
l_with PLS_INTEGER;
BEGIN
IF i_lob IS NULL
OR i_what IS NULL
OR i_offset < 1
OR i_offset > DBMS_LOB.LOBMAXSIZE
OR i_nth < 1
OR i_nth > DBMS_LOB.LOBMAXSIZE
THEN
RETURN NULL;
END IF;
n := NVL( DBMS_LOB.INSTR( i_lob, i_what, i_offset, i_nth ), 0 );
l_lob := DBMS_LOB.GETLENGTH( i_lob );
l_what := LENGTH( i_what );
l_with := NVL( DBMS_LOB.GETLENGTH( i_with ), 0 );
DBMS_LOB.CREATETEMPORARY( o_lob, FALSE );
IF n > 0 THEN
IF n > 1 THEN
DBMS_LOB.COPY( o_lob, i_lob, n-1, 1, 1 );
END IF;
IF l_with > 0 THEN
DBMS_LOB.APPEND( o_lob, i_with );
END IF;
IF n + l_what <= l_lob THEN
DBMS_LOB.COPY( o_lob, i_lob, l_lob - n - l_what + 1, n + l_with, n + l_what );
END IF;
ELSE
DBMS_LOB.APPEND( o_lob, i_lob );
END IF;
RETURN o_lob;
END;
/
Oracle 11g R2 Schema Setup:
CREATE TABLE table_name ( value clob)
/
CREATE TABLE replacements ( str VARCHAR2(4000), repl CLOB )
/
DECLARE
str VARCHAR2(4000) := 'value';
r CLOB;
c1l CLOB;
c1m CLOB;
c1r CLOB;
c2l CLOB;
c2m CLOB;
c2r CLOB;
c3l CLOB;
c3m CLOB;
c3r CLOB;
BEGIN
DBMS_LOB.CREATETEMPORARY( r, FALSE );
DBMS_LOB.CREATETEMPORARY( c1l, FALSE );
DBMS_LOB.CREATETEMPORARY( c1m, FALSE );
DBMS_LOB.CREATETEMPORARY( c1r, FALSE );
DBMS_LOB.CREATETEMPORARY( c2l, FALSE );
DBMS_LOB.CREATETEMPORARY( c2m, FALSE );
DBMS_LOB.CREATETEMPORARY( c2r, FALSE );
DBMS_LOB.CREATETEMPORARY( c3l, FALSE );
DBMS_LOB.CREATETEMPORARY( c3m, FALSE );
DBMS_LOB.CREATETEMPORARY( c3r, FALSE );
FOR i IN 1 .. 10 LOOP
DBMS_LOB.WRITEAPPEND( r, 4000, RPAD( 'y', 4000, 'y' ) );
DBMS_LOB.WRITEAPPEND( C1m, 20, RPAD( 'x', 20, 'x' ) );
DBMS_LOB.WRITEAPPEND( C1r, 40, RPAD( 'x', 40, 'x' ) );
DBMS_LOB.WRITEAPPEND( C2m, 200, RPAD( 'x', 200, 'x' ) );
DBMS_LOB.WRITEAPPEND( C2r, 400, RPAD( 'x', 400, 'x' ) );
DBMS_LOB.WRITEAPPEND( C3m, 2000, RPAD( 'x', 2000, 'x' ) );
DBMS_LOB.WRITEAPPEND( C3r, 4000, RPAD( 'x', 4000, 'x' ) );
END LOOP;
DBMS_LOB.WRITEAPPEND( c1l, 5, str );
DBMS_LOB.WRITEAPPEND( c1m, 5, str );
DBMS_LOB.WRITEAPPEND( c1r, 5, str );
DBMS_LOB.WRITEAPPEND( c2l, 5, str );
DBMS_LOB.WRITEAPPEND( c2m, 5, str );
DBMS_LOB.WRITEAPPEND( c2r, 5, str );
DBMS_LOB.WRITEAPPEND( c3l, 5, str );
DBMS_LOB.WRITEAPPEND( c3m, 5, str );
DBMS_LOB.WRITEAPPEND( c3r, 5, str );
FOR i IN 1 .. 10 LOOP
DBMS_LOB.WRITEAPPEND( C1l, 40, RPAD( 'x', 40, 'x' ) );
DBMS_LOB.WRITEAPPEND( C1m, 20, RPAD( 'x', 20, 'x' ) );
DBMS_LOB.WRITEAPPEND( C2l, 400, RPAD( 'x', 400, 'x' ) );
DBMS_LOB.WRITEAPPEND( C2m, 200, RPAD( 'x', 200, 'x' ) );
DBMS_LOB.WRITEAPPEND( C3l, 4000, RPAD( 'x', 4000, 'x' ) );
DBMS_LOB.WRITEAPPEND( C3m, 2000, RPAD( 'x', 2000, 'x' ) );
END LOOP;
INSERT INTO table_name VALUES ( NULL );
INSERT INTO table_name VALUES ( EMPTY_CLOB() );
INSERT INTO table_name VALUES ( '0123456789' );
INSERT INTO table_name VALUES ( str );
INSERT INTO table_name VALUES ( c1l );
INSERT INTO table_name VALUES ( c1m );
INSERT INTO table_name VALUES ( c1r );
INSERT INTO table_name VALUES ( c2l );
INSERT INTO table_name VALUES ( c2m );
INSERT INTO table_name VALUES ( c2r );
INSERT INTO table_name VALUES ( c3l );
INSERT INTO table_name VALUES ( c3m );
INSERT INTO table_name VALUES ( c3r );
INSERT INTO replacements VALUES ( str, r );
COMMIT;
END;
/
Query 1:
SELECT DBMS_LOB.GETLENGTH( value )
FROM table_name
Results:
| DBMS_LOB.GETLENGTH(VALUE) |
|---------------------------|
| (null) |
| 0 |
| 10 |
| 5 |
| 405 |
| 405 |
| 405 |
| 4005 |
| 4005 |
| 4005 |
| 40005 |
| 40005 |
| 40005 |
Query 2:
UPDATE table_name
SET value = LOB_REPLACE(
value,
( SELECT str FROM replacements ),
( SELECT repl FROM replacements )
)
Query 3:
SELECT DBMS_LOB.GETLENGTH( value )
FROM table_name
Results:
| DBMS_LOB.GETLENGTH(VALUE) |
|---------------------------|
| (null) |
| 0 |
| 10 |
| 40000 |
| 40400 |
| 40400 |
| 40400 |
| 44000 |
| 44000 |
| 44000 |
| 80000 |
| 80000 |
| 80000 |

Answer 3

This will do the job:
function CLOBREPLACE(
AINPUT CLOB,
APATTERN VARCHAR2,
ASUBSTITUTE CLOB
) return CLOB is
FCLOB CLOB := AINPUT;
FOFFSET INTEGER;
FCHUNK CLOB;
begin
if length(ASUBSTITUTE) > 32000 then
FOFFSET := 1;
FCLOB := replace(FCLOB, APATTERN, '###CLOBREPLACE###');
while FOFFSET <= length(ASUBSTITUTE) loop
FCHUNK := substr(ASUBSTITUTE, FOFFSET, 32000) || '###CLOBREPLACE###';
FCLOB := regexp_replace(FCLOB, '###CLOBREPLACE###', FCHUNK);
FOFFSET := FOFFSET + 32000;
end loop;
FCLOB := regexp_replace(FCLOB, '###CLOBREPLACE###', '');
else
FCLOB := replace(FCLOB, APATTERN, ASUBSTITUTE);
end if;
return FCLOB;
end;
Result of test case:
v2:32767
cl_small:32767
cl_big[1]:65535
cl_big[2]:98301
cl_big[3]:131069

Answer 4

Function REPLACE can be used for CLOB
Doc:
http://psoug.org/reference/translate_replace.html
Working sample:
declare
l_clob clob;
l_parname clob;
l_value clob;
l_par_id_obj varchar2(200) := '${id_obj}';
procedure setCLOBValue(p_CLOB in out CLOB, p_value string) as
begin
DBMS_LOB.createtemporary(p_CLOB, false);
dbms_lob.open(p_CLOB, dbms_lob.lob_readwrite);
dbms_lob.write(p_CLOB, length(p_value), 1, p_value);
dbms_lob.close(p_CLOB);
end;
begin
select SOURCE_FILE into l_clob from st_static_source_clob;
setCLOBValue(l_parname, l_par_id_obj);
setCLOBValue(l_value, '200701000024');
l_clob := replace(l_clob, l_parname, l_value);
end;

Answer 5

Below function solves the problem:
create or replace FUNCTION replace_clob
(
in_source IN CLOB,
in_search IN VARCHAR2,
in_replace IN CLOB
)
RETURN CLOB
IS
l_pos pls_integer;
out_replace_clob CLOB := in_source;
BEGIN
l_pos := instr(in_source, in_search);
IF l_pos > 0 THEN
WHILE l_pos > 0 LOOP
out_replace_clob := substr(out_replace_clob, 1, l_pos-1)
|| in_replace
|| substr(out_replace_clob, l_pos+LENGTH(in_search));
l_pos := instr(out_replace_clob, in_search);
END LOOP;
RETURN out_replace_clob;
END IF;
RETURN in_source;
END replace_clob;
/

Answer 6

This below function gives replace all functionality for CLOB datatype in Oracle PLSQL
CREATE FUNCTION lob_replaceall
(
i_lob IN clob,
i_what IN varchar2,
i_with IN clob,
i_offset IN INTEGER DEFAULT 1
) RETURN CLOB
AS
o_lob CLOB;
n PLS_INTEGER;
l_lob PLS_INTEGER;
l_what PLS_INTEGER;
l_with PLS_INTEGER;
l_temp_lob CLOB;
BEGIN
IF i_lob IS NULL
OR i_what IS NULL
OR i_offset < 1
OR i_offset > DBMS_LOB.LOBMAXSIZE
THEN
RETURN NULL;
END IF;
l_temp_lob:=i_lob;
LOOP
n := NVL( DBMS_LOB.INSTR( l_temp_lob, i_what, i_offset, 1 ), 0 );
l_lob := DBMS_LOB.GETLENGTH( l_temp_lob );
l_what := LENGTH( i_what );
l_with := NVL( DBMS_LOB.GETLENGTH( i_with ), 0 );
DBMS_LOB.CREATETEMPORARY( o_lob, FALSE );
IF n > 0 THEN
IF n > 1 THEN
DBMS_LOB.COPY( o_lob, l_temp_lob, n-1, 1, 1 );
END IF;
IF l_with > 0 THEN
DBMS_LOB.APPEND( o_lob, i_with );
END IF;
IF n + l_what <= l_lob THEN
DBMS_LOB.COPY( o_lob, l_temp_lob, l_lob - n - l_what + 1, n + l_with, n + l_what );
END IF;
ELSE
DBMS_LOB.APPEND( o_lob, l_temp_lob );
END IF;
EXIT WHEN n=0;
l_temp_lob:= o_lob;
o_lob := NULL;
END LOOP;
RETURN o_lob;
END;
/