Hi Keith, Indeed just removing the CTE creation of the DIGITS makes Dan's version up to speed.
Would the "wholenumber" external SQLite module help : - to make SQLite code cleaner ? (like "generate_series" of Postgresql, or "dual" of Oracle) - still provide the same speed-up ? Portfolio of typical Sudokus -- easy (0 sec) '53..7....6..195....98....6.8...6...34..8.3..17...2...6.6....28....419..5....8..79' -- medium (2 sec) '1....7.9..3..2...8..96..5....53..9...1..8...26....4...3......1..4......7..7...3..' -- hard (200 s) '8..........36......7..9.2...5...7.......457.....1...3...1....68..85...1..9....4..' WITH RECURSIVE input(sud) AS ( VALUES( '53..7....6..195....98....6.8...6...34..8.3..17...2...6.6....28....419..5....8..79' ) ), /* A table filled with digits 1..9, inclusive. */ digits(z, lp) AS ( VALUES('1', 1),('2', 2) ,('3', 3),('4', 4),('5', 5),('6', 6),('7', 7),('8', 8),('9', 9) ), /* The tricky bit. */ x(s, ind) AS ( SELECT sud, instr(sud, '.') FROM input UNION ALL SELECT substr(s, 1, ind-1) || z || substr(s, ind+1), instr( substr(s, 1, ind-1) || z || substr(s, ind+1), '.' ) FROM x, digits AS z WHERE ind>0 AND NOT EXISTS ( SELECT 1 FROM digits AS lp WHERE z.z = substr(s, ((ind-1)/9)*9 + lp, 1) OR z.z = substr(s, ((ind-1)%9) + (lp-1)*9 + 1, 1) OR z.z = substr(s, (((ind-1)/3) % 3) * 3 + ((ind-1)/27) * 27 + lp + ((lp-1) / 3) * 6 , 1) ) ) SELECT s FROM x WHERE ind=0; _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users