we will show and test SQL and Plsql implementations provided by ChatGPT and Gemini.
Note: Tested on Oracle 19c.
1. ChatGPT
1.1 ChatGPT SQL Implementation
Ask:
SQL-Only: Read Oracle CLOB Line by Line
Answer:
WITH clob_data AS (
SELECT your_clob_column AS clob_text
FROM your_table
WHERE your_condition
),
lines AS (
SELECT LEVEL AS line_num,
TRIM(REGEXP_SUBSTR(clob_text, '[^(\r\n)]+', 1, LEVEL)) AS line_text
FROM clob_data
CONNECT BY REGEXP_SUBSTR(clob_text, '[^(\r\n)]+', 1, LEVEL) IS NOT NULL
)
SELECT line_num, line_text
FROM lines;
----------------------- Test Procedure: Reading 1,000 Lines takes 3 Minutes -----------------------
create or replace procedure SQL_ChatGPT(p_id number) is
l_row_cnt number := power(10, p_id); -- requires rownum limit, otherwise endless loop
l_cnt number := 0;
l_len number := 0;
begin
for c in (
with clob_data as (select mylob clob_text from test_tab_lob where id = p_id),
lines AS (
SELECT LEVEL AS line_num,
TRIM(REGEXP_SUBSTR(clob_text, '[^' || chr(10) || ']+', 1, LEVEL)) AS line_text
FROM clob_data
CONNECT BY REGEXP_SUBSTR(clob_text, '[^' || chr(10) || ']+', 1, LEVEL) IS NOT NULL and rownum <=l_row_cnt
)
SELECT line_num, line_text
FROM lines
) loop
l_cnt := l_cnt + 1;
l_len := l_len + length(c.line_text);
end loop;
dbms_output.put_line('CNT = '||l_cnt ||', Length = '||l_len);
end;
/
SQL > exec SQL_ChatGPT(3);
CNT = 1,000, Length = 509,455
Elapsed: 00:03:12.20
In the original code, rownum limit condition has to be added, otherwise endless loop.
1.2 ChatGPT Plsql Implementation
Ask:
PL/SQL code to read a CLOB line by line
Answer:
DECLARE
v_clob CLOB;
v_line VARCHAR2(32767);
v_pos INTEGER := 1;
v_newline INTEGER;
v_clob_len INTEGER;
BEGIN
-- Get your CLOB (example: first row from your_table)
SELECT your_clob_column INTO v_clob FROM your_table WHERE rownum = 1;
v_clob_len := DBMS_LOB.getlength(v_clob);
WHILE v_pos <= v_clob_len LOOP
-- Find next newline position
v_newline := DBMS_LOB.INSTR(v_clob, CHR(10), v_pos);
IF v_newline = 0 THEN
-- No more newlines: read till end of CLOB
v_line := DBMS_LOL.SUBSTR(v_clob, v_clob_len - v_pos + 1, v_pos);
DBMS_OUTPUT.PUT_LINE(v_line);
EXIT;
ELSE
-- Read from current pos up to newline -1 (excluding newline)
v_line := DBMS_LOB.SUBSTR(v_clob, v_newline - v_pos, v_pos);
DBMS_OUTPUT.PUT_LINE(v_line);
-- Move position to character after newline
v_pos := v_newline + 1;
END IF;
END LOOP;
END;
----------------------- Test Procedure: Reading 100,000 Lines takes 47 Seconds -----------------------
create or replace procedure PLSQL_ChatGPT(p_id number) is
--DECLARE
v_clob CLOB;
v_line VARCHAR2(32767);
v_pos INTEGER := 1;
v_newline INTEGER;
v_clob_len INTEGER;
l_cnt number := 0;
l_len number := 0;
BEGIN
-- Get your CLOB (example: first row from your_table)
--SELECT your_clob_column INTO v_clob FROM your_table WHERE rownum = 1;
select mylob into v_clob from test_tab_lob where id = p_id;
v_clob_len := DBMS_LOB.getlength(v_clob);
WHILE v_pos <= v_clob_len LOOP
-- Find next newline position
v_newline := DBMS_LOB.INSTR(v_clob, CHR(10), v_pos);
IF v_newline = 0 THEN
-- No more newlines: read till end of CLOB
-- v_line := DBMS_LOL.SUBSTR(v_clob, v_clob_len - v_pos + 1, v_pos);
v_line := DBMS_LOB.SUBSTR(v_clob, v_clob_len - v_pos + 1, v_pos);
DBMS_OUTPUT.PUT_LINE(v_line);
EXIT;
ELSE
-- Read from current pos up to newline -1 (excluding newline)
v_line := DBMS_LOB.SUBSTR(v_clob, v_newline - v_pos, v_pos);
--DBMS_OUTPUT.PUT_LINE(v_line);
-- Move position to character after newline
v_pos := v_newline + 1;
END IF;
l_cnt := l_cnt + 1;
l_len := l_len + length(v_line);
END LOOP;
dbms_output.put_line('CNT = '||l_cnt ||', Length = '||l_len);
END;
/
SQL > exec PLSQL_ChatGPT(5);
CNT = 100,000, Length = 99,509,455
Elapsed: 00:00:47.04
2. Gemini
2.1 Gemini SQL Implementation
Ask:
read oracle clob line by line with pure recursive SQL
Answer:
WITH
clob_data AS (
-- Replace this CTE with your actual table and CLOB column
SELECT
TO_CLOB(
'This is the first line of the CLOB.' || CHR(10) ||
'Second line is here.' || CHR(10) ||
'And the very last line, third one.'
) AS my_clob
FROM
dual
),
lines_recursive (line_num, current_pos, remaining_clob, line_text) AS (
-- Anchor Member: Start with the first line
SELECT
1 AS line_num,
1 AS current_pos,
c.my_clob AS remaining_clob,
CASE
WHEN INSTR(c.my_clob, CHR(10), 1) > 0 THEN SUBSTR(c.my_clob, 1, INSTR(c.my_clob, CHR(10), 1) - 1)
ELSE c.my_clob
END AS line_text
FROM
clob_data c
UNION ALL
-- Recursive Member: Process the next line
SELECT
lr.line_num + 1 AS line_num,
INSTR(lr.remaining_clob, CHR(10), 1) + 1 AS current_pos,
SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1) AS remaining_clob,
CASE
WHEN INSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), CHR(10), 1) > 0
THEN SUBSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), 1,
INSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), CHR(10), 1) - 1)
ELSE SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1)
END AS line_text
FROM
lines_recursive lr
WHERE
INSTR(lr.remaining_clob, CHR(10), 1) > 0 -- Continue as long as there are more newlines
)
SELECT
line_num,
line_text
FROM
lines_recursive;
I'm sorry, but it is not possible to read an Oracle CLOB line by line using SQL only.'
----- Test Procedure: Reading 10,000 Lines hit "ORA-01652: unable to extend temp segment by in tablespace" ------
create or replace procedure SQL_Gemini(p_id number) is
l_cnt number := 0;
l_len number := 0;
begin
for c in (
with clob_data as (select mylob my_clob from test_tab_lob where id = p_id),
lines_recursive (line_num, current_pos, remaining_clob, line_text) AS (
-- Anchor Member: Start with the first line
SELECT
1 AS line_num,
1 AS current_pos,
c.my_clob AS remaining_clob,
CASE
WHEN INSTR(c.my_clob, CHR(10), 1) > 0 THEN SUBSTR(c.my_clob, 1, INSTR(c.my_clob, CHR(10), 1) - 1)
ELSE c.my_clob
END AS line_text
FROM
clob_data c
UNION ALL
-- Recursive Member: Process the next line
SELECT
lr.line_num + 1 AS line_num,
INSTR(lr.remaining_clob, CHR(10), 1) + 1 AS current_pos,
SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1) AS remaining_clob,
CASE
WHEN INSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), CHR(10), 1) > 0
THEN SUBSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), 1,
INSTR(SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1), CHR(10), 1) - 1)
ELSE SUBSTR(lr.remaining_clob, INSTR(lr.remaining_clob, CHR(10), 1) + 1)
END AS line_text
FROM
lines_recursive lr
WHERE
INSTR(lr.remaining_clob, CHR(10), 1) > 0 -- Continue as long as there are more newlines
)
SELECT
line_num,
line_text
FROM
lines_recursive
) loop
l_cnt := l_cnt + 1;
l_len := l_len + length(c.line_text);
end loop;
dbms_output.put_line('CNT = '||l_cnt ||', Length = '||l_len);
end;
/
SQL > exec SQL_Gemini(4);
BEGIN SQL_Gemini(4); END;
*
ERROR at line 1:
ORA-01652: unable to extend temp segment by in tablespace
ORA-06512: at "K.SQL_GEMINI", line 6
ORA-06512: at "K.SQL_GEMINI", line 6
ORA-06512: at line 1
Elapsed: 00:01:38.98
-- v$active_session_history.temp_space_allocated shows about 8 GB.
2.2 Gemini Plsql Implementation
Ask:
read oracle clob line by line with PLSQL only
Answer:
DECLARE
l_clob CLOB;
l_offset NUMBER := 1;
l_line_start NUMBER := 1;
l_line_end NUMBER;
l_line_buffer VARCHAR2(32767); -- Max PL/SQL VARCHAR2 size
l_newline_char_unix VARCHAR2(1) := CHR(10);
l_newline_char_win VARCHAR2(2) := CHR(13) || CHR(10);
l_newline_length NUMBER;
l_clob_length NUMBER;
BEGIN
-- 1. Populate a CLOB for demonstration (replace with your actual CLOB source)
l_clob := 'This is the first line.' || CHR(10) ||
'This is the second line with some more text.' || CHR(10) ||
'And a third line.' || CHR(13) || CHR(10) || -- Example with Windows newline
'Fourth line after Windows newline.' || CHR(10) ||
'Last line without a trailing newline.';
l_clob_length := DBMS_LOB.GETLENGTH(l_clob);
-- Loop through the CLOB
WHILE l_offset <= l_clob_length LOOP
-- Try to find Unix-style newline first
l_line_end := INSTR(l_clob, l_newline_char_unix, l_offset);
l_newline_length := 1; -- Length of Unix newline
-- If not found or if a Windows newline is found earlier
IF l_line_end = 0 OR (INSTR(l_clob, l_newline_char_win, l_offset) > 0 AND INSTR(l_clob, l_newline_char_win, l_offset) < l_line_end) THEN
l_line_end := INSTR(l_clob, l_newline_char_win, l_offset);
l_newline_length := 2; -- Length of Windows newline
END IF;
IF l_line_end = 0 THEN
-- No more newlines found, this is the last "line" (or the only line)
l_line_buffer := DBMS_LOB.SUBSTR(l_clob, l_clob_length - l_offset + 1, l_offset);
l_offset := l_clob_length + 1; -- Exit loop
ELSE
-- Newline found, extract the line
l_line_buffer := DBMS_LOB.SUBSTR(l_clob, l_line_end - l_offset, l_offset);
l_offset := l_line_end + l_newline_length;
END IF;
-- Process the extracted line
DBMS_OUTPUT.PUT_LINE('Line: "' || l_line_buffer || '"');
END LOOP;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('An error occurred: ' || SQLERRM);
END;
/
----------------------- Test Procedure: Reading 100,000 Lines takes 44 Seconds -----------------------
-- Remove l_newline_char_win check, only check l_newline_char_unix
-- If check both l_newline_char_win and l_newline_char_unix, it takes
create or replace procedure PLSQL_Gemini(p_id number, p_check_both number:= 0) is
l_clob CLOB;
l_offset NUMBER := 1;
l_line_start NUMBER := 1;
l_line_end NUMBER;
l_line_buffer VARCHAR2(32767); -- Max PL/SQL VARCHAR2 size
l_newline_char_unix VARCHAR2(1) := CHR(10);
l_newline_char_win VARCHAR2(2) := CHR(13) || CHR(10);
l_newline_length NUMBER;
l_clob_length NUMBER;
l_cnt number := 0;
l_len number := 0;
BEGIN
-- 1. Populate a CLOB for demonstration (replace with your actual CLOB source)
select mylob into l_clob from test_tab_lob where id = p_id;
l_clob_length := DBMS_LOB.GETLENGTH(l_clob);
-- Loop through the CLOB
WHILE l_offset <= l_clob_length LOOP
-- Try to find Unix-style newline first
l_line_end := INSTR(l_clob, l_newline_char_unix, l_offset);
l_newline_length := 1; -- Length of Unix newline
-- If not found or if a Windows newline is found earlier
if p_check_both > 0 then
IF l_line_end = 0 OR (INSTR(l_clob, l_newline_char_win, l_offset) > 0 AND INSTR(l_clob, l_newline_char_win, l_offset) < l_line_end) THEN
l_line_end := INSTR(l_clob, l_newline_char_win, l_offset);
l_newline_length := 2; -- Length of Windows newline
END IF;
end if;
IF l_line_end = 0 THEN
-- No more newlines found, this is the last "line" (or the only line)
l_line_buffer := DBMS_LOB.SUBSTR(l_clob, l_clob_length - l_offset + 1, l_offset);
l_offset := l_clob_length + 1; -- Exit loop
ELSE
-- Newline found, extract the line
l_line_buffer := DBMS_LOB.SUBSTR(l_clob, l_line_end - l_offset, l_offset);
l_offset := l_line_end + l_newline_length;
END IF;
-- Process the extracted line
--DBMS_OUTPUT.PUT_LINE('Line: "' || l_line_buffer || '"');
l_cnt := l_cnt + 1;
l_len := l_len + length(l_line_buffer);
END LOOP;
dbms_output.put_line('CNT = '||l_cnt ||', Length = '||l_len);
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('An error occurred: ' || SQLERRM);
END;
/
-- Remove l_newline_char_win check, only check l_newline_char_unix
SQL > exec PLSQL_Gemini(5, 0);
CNT = 100,000, Length = 99,509,455
Elapsed: 00:00:44.32
-- Check both l_newline_char_win and l_newline_char_unix
SQL > exec PLSQL_Gemini(4, 1);
$> perf top -d 2 -p 2464404
PerfTop: 2337 irqs/sec kernel: 0.0% exact: 0.0% lost: 0/0 drop: 0/0 [4000Hz cpu-clock:uhpppH], (target_pid: 2464404)
-------------------------------------------------------------------------------------------------------------------------------------------
42.87% oracle [.] kole_simple_string_match
31.51% oracle [.] _intel_fast_memcmp
2.50% oracle [.] kcbgtcr
1.97% libc-2.28.so [.] syscall
1.02% oracle [.] sxorchk
0.86% oracle [.] __intel_avx_rep_memcpy
3. Test Outcome
3.1. ChatGPT SQL
SQL > exec SQL_ChatGPT(3);
CNT = 1,000, Length = 509,455
Elapsed: 00:03:04.59
SQL > exec SQL_ChatGPT(4);
CNT = 10,000, Length = 9,509,455
Elapsed: 08:20:01.13
SQL > exec SQL_ChatGPT(5);
-- Not finished after 10 hours
3.2. ChatGPT PLSQL
SQL > exec PLSQL_ChatGPT(3);
CNT = 1,000, Length = 509,455
Elapsed: 00:00:00.38
SQL > exec PLSQL_ChatGPT(4);
CNT = 10,000, Length = 9,509,455
Elapsed: 00:00:04.04
SQL > exec PLSQL_ChatGPT(5);
CNT = 100,000, Length = 99,509,455
Elapsed: 00:00:36.66
3.3. Gemini SQL
SQL > exec SQL_Gemini(3);
CNT = 1001, Length = 509455
Elapsed: 00:00:05.60
SQL > exec SQL_Gemini(4);
BEGIN SQL_Gemini(4); END;
*
ERROR at line 1:
ORA-01652: unable to extend temp segment by in tablespace
ORA-06512: at "K.SQL_GEMINI", line 6
ORA-06512: at "K.SQL_GEMINI", line 6
ORA-06512: at line 1
Elapsed: 00:01:35.50
3.4. Gemini PLSQL
SQL > exec PLSQL_Gemini(3);
CNT = 1,000, Length = 509,455
Elapsed: 00:00:00.35
SQL > exec PLSQL_Gemini(4);
CNT = 10,000, Length = 9,509,455
Elapsed: 00:00:04.28
SQL > exec PLSQL_Gemini(5);
CNT = 100,000, Length = 99,509,455
Elapsed: 00:00:38.75
3.5. Test Summary
(A). Both ChatGPT and Gemini provided efficient Plsql implementations.
(B). ChatGPT SQL implementation has the similar performance as SQL_SLOW in previous Blog (heavy "direct path read").
(C). Germin SQL implementation hits "ORA-01652: unable to extend temp segment by in tablespace" for 10,000 CLOB lines.
(D). Small adaptations/fixes could be needed to make them runnable.
