executor: fix index out of range panic of cte when max_chunk_size is samll (#48839)

close #48808

Author: guo-shaoge

pkg/executor/cte.go

@@ -546,6 +546,16 @@ func (p *cteProducer) computeChunkHash(chk *chunk.Chunk) (sel []int, err error)
 			hashBitMap[val] = true
 		}
 	} else {
+		// Length of p.sel is init as MaxChunkSize, but the row num of chunk may still exceeds MaxChunkSize.
+		// So needs to handle here to make sure len(p.sel) == chk.NumRows().
+		if len(p.sel) < numRows {
+			tmpSel := make([]int, numRows-len(p.sel))
+			for i := 0; i < len(tmpSel); i++ {
+				tmpSel[i] = i + len(p.sel)
+			}
+			p.sel = append(p.sel, tmpSel...)
+		}
+
 		// All rows is selected, sel will be [0....numRows).
 		// e.sel is setup when building executor.
 		sel = p.sel

tests/integrationtest/r/executor/cte.result

@@ -1,4 +1,3 @@
-set tidb_max_chunk_size=default;
 with recursive cte1 as (select 1 c1 union all select c1 + 1 c1 from cte1 where c1 < 5) select * from cte1;
 c1
 1
@@ -406,3 +405,11 @@ a
 1
 use executor__cte;
 drop database executor__cte1;
+set tidb_max_chunk_size=32;
+drop table if exists t1;
+create table t1(c1 int);
+insert into t1 values(0), (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17), (18), (19), (20), (21), (22), (23), (24), (25), (26), (27), (28), (29), (30), (31), (32), (33), (34), (35), (36), (37), (38), (39), (40), (41), (42), (43), (44), (45), (46), (47), (48), (49), (50), (51), (52), (53), (54), (55), (56), (57), (58), (59), (60), (61), (62), (63), (64), (65), (66), (67), (68), (69), (70), (71), (72), (73), (74), (75), (76), (77), (78), (79), (80), (81), (82), (83), (84), (85), (86), (87), (88), (89), (90), (91), (92), (93), (94), (95), (96), (97), (98), (99), (100), (101), (102), (103), (104), (105), (106), (107), (108), (109), (110), (111), (112), (113), (114), (115), (116), (117), (118), (119), (120), (121), (122), (123), (124), (125), (126), (127), (128), (129), (130), (131), (132), (133), (134), (135), (136), (137), (138), (139), (140), (141), (142), (143), (144), (145), (146), (147), (148), (149), (150), (151), (152), (153), (154), (155), (156), (157), (158), (159), (160), (161), (162), (163), (164), (165), (166), (167), (168), (169), (170), (171), (172), (173), (174), (175), (176), (177), (178), (179), (180), (181), (182), (183), (184), (185), (186), (187), (188), (189), (190), (191), (192), (193), (194), (195), (196), (197), (198), (199), (200), (201), (202), (203), (204), (205), (206), (207), (208), (209), (210), (211), (212), (213), (214), (215), (216), (217), (218), (219), (220), (221), (222), (223), (224), (225), (226), (227), (228), (229), (230), (231), (232), (233), (234), (235), (236), (237), (238), (239), (240), (241), (242), (243), (244), (245), (246), (247), (248), (249), (250), (251), (252), (253), (254), (255), (256), (257), (258), (259), (260), (261), (262), (263), (264), (265), (266), (267), (268), (269), (270), (271), (272), (273), (274), (275), (276), (277), (278), (279), (280), (281), (282), (283), (284), (285), (286), (287), (288), (289), (290), (291), (292), (293), (294), (295), (296), (297), (298), (299);
+with recursive cte1(c1) as (select c1 from t1 union select c1 + 1 c1 from cte1 limit 1 offset 100) select * from cte1;
+c1
+100
+set tidb_max_chunk_size=default;

tests/integrationtest/t/executor/cte.test

@@ -1,6 +1,3 @@
-## Delete it when https://github.com/pingcap/tidb/issues/48808 merged
-set tidb_max_chunk_size=default;
-
 # TestBasicCTE
 with recursive cte1 as (select 1 c1 union all select c1 + 1 c1 from cte1 where c1 < 5) select * from cte1;
 with recursive cte1 as (select 1 c1 union all select 2 c1 union all select c1 + 1 c1 from cte1 where c1 < 10) select * from cte1 order by c1;
@@ -148,3 +145,11 @@ use executor__cte1;
 select * from executor__cte.v;
 use executor__cte;
 drop database executor__cte1;
+
+# TestCTEMaxChunkSizeIsSmall
+set tidb_max_chunk_size=32;
+drop table if exists t1;
+create table t1(c1 int);
+insert into t1 values(0), (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14), (15), (16), (17), (18), (19), (20), (21), (22), (23), (24), (25), (26), (27), (28), (29), (30), (31), (32), (33), (34), (35), (36), (37), (38), (39), (40), (41), (42), (43), (44), (45), (46), (47), (48), (49), (50), (51), (52), (53), (54), (55), (56), (57), (58), (59), (60), (61), (62), (63), (64), (65), (66), (67), (68), (69), (70), (71), (72), (73), (74), (75), (76), (77), (78), (79), (80), (81), (82), (83), (84), (85), (86), (87), (88), (89), (90), (91), (92), (93), (94), (95), (96), (97), (98), (99), (100), (101), (102), (103), (104), (105), (106), (107), (108), (109), (110), (111), (112), (113), (114), (115), (116), (117), (118), (119), (120), (121), (122), (123), (124), (125), (126), (127), (128), (129), (130), (131), (132), (133), (134), (135), (136), (137), (138), (139), (140), (141), (142), (143), (144), (145), (146), (147), (148), (149), (150), (151), (152), (153), (154), (155), (156), (157), (158), (159), (160), (161), (162), (163), (164), (165), (166), (167), (168), (169), (170), (171), (172), (173), (174), (175), (176), (177), (178), (179), (180), (181), (182), (183), (184), (185), (186), (187), (188), (189), (190), (191), (192), (193), (194), (195), (196), (197), (198), (199), (200), (201), (202), (203), (204), (205), (206), (207), (208), (209), (210), (211), (212), (213), (214), (215), (216), (217), (218), (219), (220), (221), (222), (223), (224), (225), (226), (227), (228), (229), (230), (231), (232), (233), (234), (235), (236), (237), (238), (239), (240), (241), (242), (243), (244), (245), (246), (247), (248), (249), (250), (251), (252), (253), (254), (255), (256), (257), (258), (259), (260), (261), (262), (263), (264), (265), (266), (267), (268), (269), (270), (271), (272), (273), (274), (275), (276), (277), (278), (279), (280), (281), (282), (283), (284), (285), (286), (287), (288), (289), (290), (291), (292), (293), (294), (295), (296), (297), (298), (299);
+with recursive cte1(c1) as (select c1 from t1 union select c1 + 1 c1 from cte1 limit 1 offset 100) select * from cte1;
+set tidb_max_chunk_size=default;