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# Utility function to extract only a certain
# JSON object/array from some optimizer trace.
# @param extract a string of the form 'XXX S'
# where XXX is object or array's key, and S is the symbol after this
# key ( [ or { ).
--disable_query_log
DELIMITER |;
CREATE FUNCTION show_json_object(extract TEXT, trace LONGTEXT)
RETURNS TEXT
BEGIN
DECLARE pos INT;
DECLARE opened INT;
DECLARE closed INT;
DECLARE inside INT;
DECLARE stop INT;
DECLARE open_symbol VARCHAR(1);
DECLARE close_symbol VARCHAR(1);
SET pos = LOCATE(extract, trace);
IF pos = 0
THEN
RETURN 'NOT FOUND';
END IF;
SET open_symbol = SUBSTRING(extract, -1);
IF open_symbol = '{'
THEN
SET close_symbol = '}';
ELSEIF open_symbol = '['
THEN
SET close_symbol = ']';
ELSE
RETURN 'ERROR: 1st argument does not end with { or [';
END IF;
SET trace = SUBSTRING(trace, pos);
SET pos = 1;
SET inside = 0;
# A counter to break an infinite loop, in case of bug in SP or bad trace
SET stop = 1000;
LOOP
SET stop = stop - 1;
IF stop = 0
THEN
RETURN "ERROR";
END IF;
SET closed = LOCATE(close_symbol, trace, pos);
SET opened = LOCATE(open_symbol, trace, pos);
IF opened = 0
THEN
# symbol not found, treat it as "very far ahead"
SET opened = 2000000;
END IF;
IF opened < closed
THEN
SET inside = inside + 1;
SET pos = opened + 1;
ELSE
SET inside = inside - 1;
SET pos = closed + 1;
END IF;
IF inside = 0
THEN
RETURN SUBSTRING(trace, 1, pos);
END IF;
END LOOP;
END|
DELIMITER ;|
--enable_query_log
|
