Bug#33362: Query cache invalidation (truncate) may hang

           if cached query uses many tables

The problem was that query cache would not properly cache
queries which used 256 or more tables but yet would leave
behind query cache blocks pointing to freed (destroyed)
data. Later when invalidating (due to a truncate) query cache
would attempt to grab a lock which resided in the freed data,
leading to hangs or undefined behavior.

This was happening due to a improper return value from the
function responsible for registering the tables used in the
query (so the cache can be invalidated later if one of the
tables is modified). The function expected a return value of
type boolean (char, 8 bits) indicating success (1) or failure
(0) but the number of tables registered (unsigned int, 32 bits)
was being returned instead. This caused the function to return
failure for cases where it had actually succeed because when
a type (unsigned int) is converted to a narrower type (char),
the excess bits on the left are discarded. Thus if the 8
rightmost bits are zero, the return value will be 0 (failure).

The solution is to simply return true (1) only if the number of
registered table is greater than zero and false (0) otherwise.

mysql-test/r/query_cache_merge.result:
  Add test case result for Bug#33362
mysql-test/t/query_cache_merge.test:
  Add test case for Bug#33362
sql/sql_cache.cc:
  Return 1 or 0 depending on the number of registered tables.

mysql-test/r/query_cache_merge.result

@@ -19,3 +19,1677 @@ Qcache_queries_in_cache	0
 drop table t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13,t14,t15,t16,t17,t18,t19,t20,t21,t22,t23,t24,t25,t26,t27,t28,t29,t30,t31,t32,t33,t34,t35,t36,t37,t38,t39,t40,t41,t42,t43,t44,t45,t46,t47,t48,t49,t50,t51,t52,t53,t54,t55,t56,t57,t58,t59,t60,t61,t62,t63,t64,t65,t66,t67,t68,t69,t70,t71,t72,t73,t74,t75,t76,t77,t78,t79,t80,t81,t82,t83,t84,t85,t86,t87,t88,t89,t90,t91,t92,t93,t94,t95,t96,t97,t98,t99,t100,t101,t102,t103,t104,t105,t106,t107,t108,t109,t110,t111,t112,t113,t114,t115,t116,t117,t118,t119,t120,t121,t122,t123,t124,t125,t126,t127,t128,t129,t130,t131,t132,t133,t134,t135,t136,t137,t138,t139,t140,t141,t142,t143,t144,t145,t146,t147,t148,t149,t150,t151,t152,t153,t154,t155,t156,t157,t158,t159,t160,t161,t162,t163,t164,t165,t166,t167,t168,t169,t170,t171,t172,t173,t174,t175,t176,t177,t178,t179,t180,t181,t182,t183,t184,t185,t186,t187,t188,t189,t190,t191,t192,t193,t194,t195,t196,t197,t198,t199,t200,t201,t202,t203,t204,t205,t206,t207,t208,t209,t210,t211,t212,t213,t214,t215,t216,t217,t218,t219,t220,t221,t222,t223,t224,t225,t226,t227,t228,t229,t230,t231,t232,t233,t234,t235,t236,t237,t238,t239,t240,t241,t242,t243,t244,t245,t246,t247,t248,t249,t250,t251,t252,t253,t254,t255,t256,t257,t00;
 SET @@global.query_cache_size=0;
 set @@global.table_definition_cache=@save_table_definition_cache;
+SET @save_table_definition_cache = @@global.table_definition_cache;
+SET @@global.table_definition_cache = 512;
+CREATE TABLE t255 (a INT);
+INSERT INTO t255 VALUES (255);
+CREATE TABLE t254 (a INT);
+INSERT INTO t254 VALUES (254);
+CREATE TABLE t253 (a INT);
+INSERT INTO t253 VALUES (253);
+CREATE TABLE t252 (a INT);
+INSERT INTO t252 VALUES (252);
+CREATE TABLE t251 (a INT);
+INSERT INTO t251 VALUES (251);
+CREATE TABLE t250 (a INT);
+INSERT INTO t250 VALUES (250);
+CREATE TABLE t249 (a INT);
+INSERT INTO t249 VALUES (249);
+CREATE TABLE t248 (a INT);
+INSERT INTO t248 VALUES (248);
+CREATE TABLE t247 (a INT);
+INSERT INTO t247 VALUES (247);
+CREATE TABLE t246 (a INT);
+INSERT INTO t246 VALUES (246);
+CREATE TABLE t245 (a INT);
+INSERT INTO t245 VALUES (245);
+CREATE TABLE t244 (a INT);
+INSERT INTO t244 VALUES (244);
+CREATE TABLE t243 (a INT);
+INSERT INTO t243 VALUES (243);
+CREATE TABLE t242 (a INT);
+INSERT INTO t242 VALUES (242);
+CREATE TABLE t241 (a INT);
+INSERT INTO t241 VALUES (241);
+CREATE TABLE t240 (a INT);
+INSERT INTO t240 VALUES (240);
+CREATE TABLE t239 (a INT);
+INSERT INTO t239 VALUES (239);
+CREATE TABLE t238 (a INT);
+INSERT INTO t238 VALUES (238);
+CREATE TABLE t237 (a INT);
+INSERT INTO t237 VALUES (237);
+CREATE TABLE t236 (a INT);
+INSERT INTO t236 VALUES (236);
+CREATE TABLE t235 (a INT);
+INSERT INTO t235 VALUES (235);
+CREATE TABLE t234 (a INT);
+INSERT INTO t234 VALUES (234);
+CREATE TABLE t233 (a INT);
+INSERT INTO t233 VALUES (233);
+CREATE TABLE t232 (a INT);
+INSERT INTO t232 VALUES (232);
+CREATE TABLE t231 (a INT);
+INSERT INTO t231 VALUES (231);
+CREATE TABLE t230 (a INT);
+INSERT INTO t230 VALUES (230);
+CREATE TABLE t229 (a INT);
+INSERT INTO t229 VALUES (229);
+CREATE TABLE t228 (a INT);
+INSERT INTO t228 VALUES (228);
+CREATE TABLE t227 (a INT);
+INSERT INTO t227 VALUES (227);
+CREATE TABLE t226 (a INT);
+INSERT INTO t226 VALUES (226);
+CREATE TABLE t225 (a INT);
+INSERT INTO t225 VALUES (225);
+CREATE TABLE t224 (a INT);
+INSERT INTO t224 VALUES (224);
+CREATE TABLE t223 (a INT);
+INSERT INTO t223 VALUES (223);
+CREATE TABLE t222 (a INT);
+INSERT INTO t222 VALUES (222);
+CREATE TABLE t221 (a INT);
+INSERT INTO t221 VALUES (221);
+CREATE TABLE t220 (a INT);
+INSERT INTO t220 VALUES (220);
+CREATE TABLE t219 (a INT);
+INSERT INTO t219 VALUES (219);
+CREATE TABLE t218 (a INT);
+INSERT INTO t218 VALUES (218);
+CREATE TABLE t217 (a INT);
+INSERT INTO t217 VALUES (217);
+CREATE TABLE t216 (a INT);
+INSERT INTO t216 VALUES (216);
+CREATE TABLE t215 (a INT);
+INSERT INTO t215 VALUES (215);
+CREATE TABLE t214 (a INT);
+INSERT INTO t214 VALUES (214);
+CREATE TABLE t213 (a INT);
+INSERT INTO t213 VALUES (213);
+CREATE TABLE t212 (a INT);
+INSERT INTO t212 VALUES (212);
+CREATE TABLE t211 (a INT);
+INSERT INTO t211 VALUES (211);
+CREATE TABLE t210 (a INT);
+INSERT INTO t210 VALUES (210);
+CREATE TABLE t209 (a INT);
+INSERT INTO t209 VALUES (209);
+CREATE TABLE t208 (a INT);
+INSERT INTO t208 VALUES (208);
+CREATE TABLE t207 (a INT);
+INSERT INTO t207 VALUES (207);
+CREATE TABLE t206 (a INT);
+INSERT INTO t206 VALUES (206);
+CREATE TABLE t205 (a INT);
+INSERT INTO t205 VALUES (205);
+CREATE TABLE t204 (a INT);
+INSERT INTO t204 VALUES (204);
+CREATE TABLE t203 (a INT);
+INSERT INTO t203 VALUES (203);
+CREATE TABLE t202 (a INT);
+INSERT INTO t202 VALUES (202);
+CREATE TABLE t201 (a INT);
+INSERT INTO t201 VALUES (201);
+CREATE TABLE t200 (a INT);
+INSERT INTO t200 VALUES (200);
+CREATE TABLE t199 (a INT);
+INSERT INTO t199 VALUES (199);
+CREATE TABLE t198 (a INT);
+INSERT INTO t198 VALUES (198);
+CREATE TABLE t197 (a INT);
+INSERT INTO t197 VALUES (197);
+CREATE TABLE t196 (a INT);
+INSERT INTO t196 VALUES (196);
+CREATE TABLE t195 (a INT);
+INSERT INTO t195 VALUES (195);
+CREATE TABLE t194 (a INT);
+INSERT INTO t194 VALUES (194);
+CREATE TABLE t193 (a INT);
+INSERT INTO t193 VALUES (193);
+CREATE TABLE t192 (a INT);
+INSERT INTO t192 VALUES (192);
+CREATE TABLE t191 (a INT);
+INSERT INTO t191 VALUES (191);
+CREATE TABLE t190 (a INT);
+INSERT INTO t190 VALUES (190);
+CREATE TABLE t189 (a INT);
+INSERT INTO t189 VALUES (189);
+CREATE TABLE t188 (a INT);
+INSERT INTO t188 VALUES (188);
+CREATE TABLE t187 (a INT);
+INSERT INTO t187 VALUES (187);
+CREATE TABLE t186 (a INT);
+INSERT INTO t186 VALUES (186);
+CREATE TABLE t185 (a INT);
+INSERT INTO t185 VALUES (185);
+CREATE TABLE t184 (a INT);
+INSERT INTO t184 VALUES (184);
+CREATE TABLE t183 (a INT);
+INSERT INTO t183 VALUES (183);
+CREATE TABLE t182 (a INT);
+INSERT INTO t182 VALUES (182);
+CREATE TABLE t181 (a INT);
+INSERT INTO t181 VALUES (181);
+CREATE TABLE t180 (a INT);
+INSERT INTO t180 VALUES (180);
+CREATE TABLE t179 (a INT);
+INSERT INTO t179 VALUES (179);
+CREATE TABLE t178 (a INT);
+INSERT INTO t178 VALUES (178);
+CREATE TABLE t177 (a INT);
+INSERT INTO t177 VALUES (177);
+CREATE TABLE t176 (a INT);
+INSERT INTO t176 VALUES (176);
+CREATE TABLE t175 (a INT);
+INSERT INTO t175 VALUES (175);
+CREATE TABLE t174 (a INT);
+INSERT INTO t174 VALUES (174);
+CREATE TABLE t173 (a INT);
+INSERT INTO t173 VALUES (173);
+CREATE TABLE t172 (a INT);
+INSERT INTO t172 VALUES (172);
+CREATE TABLE t171 (a INT);
+INSERT INTO t171 VALUES (171);
+CREATE TABLE t170 (a INT);
+INSERT INTO t170 VALUES (170);
+CREATE TABLE t169 (a INT);
+INSERT INTO t169 VALUES (169);
+CREATE TABLE t168 (a INT);
+INSERT INTO t168 VALUES (168);
+CREATE TABLE t167 (a INT);
+INSERT INTO t167 VALUES (167);
+CREATE TABLE t166 (a INT);
+INSERT INTO t166 VALUES (166);
+CREATE TABLE t165 (a INT);
+INSERT INTO t165 VALUES (165);
+CREATE TABLE t164 (a INT);
+INSERT INTO t164 VALUES (164);
+CREATE TABLE t163 (a INT);
+INSERT INTO t163 VALUES (163);
+CREATE TABLE t162 (a INT);
+INSERT INTO t162 VALUES (162);
+CREATE TABLE t161 (a INT);
+INSERT INTO t161 VALUES (161);
+CREATE TABLE t160 (a INT);
+INSERT INTO t160 VALUES (160);
+CREATE TABLE t159 (a INT);
+INSERT INTO t159 VALUES (159);
+CREATE TABLE t158 (a INT);
+INSERT INTO t158 VALUES (158);
+CREATE TABLE t157 (a INT);
+INSERT INTO t157 VALUES (157);
+CREATE TABLE t156 (a INT);
+INSERT INTO t156 VALUES (156);
+CREATE TABLE t155 (a INT);
+INSERT INTO t155 VALUES (155);
+CREATE TABLE t154 (a INT);
+INSERT INTO t154 VALUES (154);
+CREATE TABLE t153 (a INT);
+INSERT INTO t153 VALUES (153);
+CREATE TABLE t152 (a INT);
+INSERT INTO t152 VALUES (152);
+CREATE TABLE t151 (a INT);
+INSERT INTO t151 VALUES (151);
+CREATE TABLE t150 (a INT);
+INSERT INTO t150 VALUES (150);
+CREATE TABLE t149 (a INT);
+INSERT INTO t149 VALUES (149);
+CREATE TABLE t148 (a INT);
+INSERT INTO t148 VALUES (148);
+CREATE TABLE t147 (a INT);
+INSERT INTO t147 VALUES (147);
+CREATE TABLE t146 (a INT);
+INSERT INTO t146 VALUES (146);
+CREATE TABLE t145 (a INT);
+INSERT INTO t145 VALUES (145);
+CREATE TABLE t144 (a INT);
+INSERT INTO t144 VALUES (144);
+CREATE TABLE t143 (a INT);
+INSERT INTO t143 VALUES (143);
+CREATE TABLE t142 (a INT);
+INSERT INTO t142 VALUES (142);
+CREATE TABLE t141 (a INT);
+INSERT INTO t141 VALUES (141);
+CREATE TABLE t140 (a INT);
+INSERT INTO t140 VALUES (140);
+CREATE TABLE t139 (a INT);
+INSERT INTO t139 VALUES (139);
+CREATE TABLE t138 (a INT);
+INSERT INTO t138 VALUES (138);
+CREATE TABLE t137 (a INT);
+INSERT INTO t137 VALUES (137);
+CREATE TABLE t136 (a INT);
+INSERT INTO t136 VALUES (136);
+CREATE TABLE t135 (a INT);
+INSERT INTO t135 VALUES (135);
+CREATE TABLE t134 (a INT);
+INSERT INTO t134 VALUES (134);
+CREATE TABLE t133 (a INT);
+INSERT INTO t133 VALUES (133);
+CREATE TABLE t132 (a INT);
+INSERT INTO t132 VALUES (132);
+CREATE TABLE t131 (a INT);
+INSERT INTO t131 VALUES (131);
+CREATE TABLE t130 (a INT);
+INSERT INTO t130 VALUES (130);
+CREATE TABLE t129 (a INT);
+INSERT INTO t129 VALUES (129);
+CREATE TABLE t128 (a INT);
+INSERT INTO t128 VALUES (128);
+CREATE TABLE t127 (a INT);
+INSERT INTO t127 VALUES (127);
+CREATE TABLE t126 (a INT);
+INSERT INTO t126 VALUES (126);
+CREATE TABLE t125 (a INT);
+INSERT INTO t125 VALUES (125);
+CREATE TABLE t124 (a INT);
+INSERT INTO t124 VALUES (124);
+CREATE TABLE t123 (a INT);
+INSERT INTO t123 VALUES (123);
+CREATE TABLE t122 (a INT);
+INSERT INTO t122 VALUES (122);
+CREATE TABLE t121 (a INT);
+INSERT INTO t121 VALUES (121);
+CREATE TABLE t120 (a INT);
+INSERT INTO t120 VALUES (120);
+CREATE TABLE t119 (a INT);
+INSERT INTO t119 VALUES (119);
+CREATE TABLE t118 (a INT);
+INSERT INTO t118 VALUES (118);
+CREATE TABLE t117 (a INT);
+INSERT INTO t117 VALUES (117);
+CREATE TABLE t116 (a INT);
+INSERT INTO t116 VALUES (116);
+CREATE TABLE t115 (a INT);
+INSERT INTO t115 VALUES (115);
+CREATE TABLE t114 (a INT);
+INSERT INTO t114 VALUES (114);
+CREATE TABLE t113 (a INT);
+INSERT INTO t113 VALUES (113);
+CREATE TABLE t112 (a INT);
+INSERT INTO t112 VALUES (112);
+CREATE TABLE t111 (a INT);
+INSERT INTO t111 VALUES (111);
+CREATE TABLE t110 (a INT);
+INSERT INTO t110 VALUES (110);
+CREATE TABLE t109 (a INT);
+INSERT INTO t109 VALUES (109);
+CREATE TABLE t108 (a INT);
+INSERT INTO t108 VALUES (108);
+CREATE TABLE t107 (a INT);
+INSERT INTO t107 VALUES (107);
+CREATE TABLE t106 (a INT);
+INSERT INTO t106 VALUES (106);
+CREATE TABLE t105 (a INT);
+INSERT INTO t105 VALUES (105);
+CREATE TABLE t104 (a INT);
+INSERT INTO t104 VALUES (104);
+CREATE TABLE t103 (a INT);
+INSERT INTO t103 VALUES (103);
+CREATE TABLE t102 (a INT);
+INSERT INTO t102 VALUES (102);
+CREATE TABLE t101 (a INT);
+INSERT INTO t101 VALUES (101);
+CREATE TABLE t100 (a INT);
+INSERT INTO t100 VALUES (100);
+CREATE TABLE t99 (a INT);
+INSERT INTO t99 VALUES (99);
+CREATE TABLE t98 (a INT);
+INSERT INTO t98 VALUES (98);
+CREATE TABLE t97 (a INT);
+INSERT INTO t97 VALUES (97);
+CREATE TABLE t96 (a INT);
+INSERT INTO t96 VALUES (96);
+CREATE TABLE t95 (a INT);
+INSERT INTO t95 VALUES (95);
+CREATE TABLE t94 (a INT);
+INSERT INTO t94 VALUES (94);
+CREATE TABLE t93 (a INT);
+INSERT INTO t93 VALUES (93);
+CREATE TABLE t92 (a INT);
+INSERT INTO t92 VALUES (92);
+CREATE TABLE t91 (a INT);
+INSERT INTO t91 VALUES (91);
+CREATE TABLE t90 (a INT);
+INSERT INTO t90 VALUES (90);
+CREATE TABLE t89 (a INT);
+INSERT INTO t89 VALUES (89);
+CREATE TABLE t88 (a INT);
+INSERT INTO t88 VALUES (88);
+CREATE TABLE t87 (a INT);
+INSERT INTO t87 VALUES (87);
+CREATE TABLE t86 (a INT);
+INSERT INTO t86 VALUES (86);
+CREATE TABLE t85 (a INT);
+INSERT INTO t85 VALUES (85);
+CREATE TABLE t84 (a INT);
+INSERT INTO t84 VALUES (84);
+CREATE TABLE t83 (a INT);
+INSERT INTO t83 VALUES (83);
+CREATE TABLE t82 (a INT);
+INSERT INTO t82 VALUES (82);
+CREATE TABLE t81 (a INT);
+INSERT INTO t81 VALUES (81);
+CREATE TABLE t80 (a INT);
+INSERT INTO t80 VALUES (80);
+CREATE TABLE t79 (a INT);
+INSERT INTO t79 VALUES (79);
+CREATE TABLE t78 (a INT);
+INSERT INTO t78 VALUES (78);
+CREATE TABLE t77 (a INT);
+INSERT INTO t77 VALUES (77);
+CREATE TABLE t76 (a INT);
+INSERT INTO t76 VALUES (76);
+CREATE TABLE t75 (a INT);
+INSERT INTO t75 VALUES (75);
+CREATE TABLE t74 (a INT);
+INSERT INTO t74 VALUES (74);
+CREATE TABLE t73 (a INT);
+INSERT INTO t73 VALUES (73);
+CREATE TABLE t72 (a INT);
+INSERT INTO t72 VALUES (72);
+CREATE TABLE t71 (a INT);
+INSERT INTO t71 VALUES (71);
+CREATE TABLE t70 (a INT);
+INSERT INTO t70 VALUES (70);
+CREATE TABLE t69 (a INT);
+INSERT INTO t69 VALUES (69);
+CREATE TABLE t68 (a INT);
+INSERT INTO t68 VALUES (68);
+CREATE TABLE t67 (a INT);
+INSERT INTO t67 VALUES (67);
+CREATE TABLE t66 (a INT);
+INSERT INTO t66 VALUES (66);
+CREATE TABLE t65 (a INT);
+INSERT INTO t65 VALUES (65);
+CREATE TABLE t64 (a INT);
+INSERT INTO t64 VALUES (64);
+CREATE TABLE t63 (a INT);
+INSERT INTO t63 VALUES (63);
+CREATE TABLE t62 (a INT);
+INSERT INTO t62 VALUES (62);
+CREATE TABLE t61 (a INT);
+INSERT INTO t61 VALUES (61);
+CREATE TABLE t60 (a INT);
+INSERT INTO t60 VALUES (60);
+CREATE TABLE t59 (a INT);
+INSERT INTO t59 VALUES (59);
+CREATE TABLE t58 (a INT);
+INSERT INTO t58 VALUES (58);
+CREATE TABLE t57 (a INT);
+INSERT INTO t57 VALUES (57);
+CREATE TABLE t56 (a INT);
+INSERT INTO t56 VALUES (56);
+CREATE TABLE t55 (a INT);
+INSERT INTO t55 VALUES (55);
+CREATE TABLE t54 (a INT);
+INSERT INTO t54 VALUES (54);
+CREATE TABLE t53 (a INT);
+INSERT INTO t53 VALUES (53);
+CREATE TABLE t52 (a INT);
+INSERT INTO t52 VALUES (52);
+CREATE TABLE t51 (a INT);
+INSERT INTO t51 VALUES (51);
+CREATE TABLE t50 (a INT);
+INSERT INTO t50 VALUES (50);
+CREATE TABLE t49 (a INT);
+INSERT INTO t49 VALUES (49);
+CREATE TABLE t48 (a INT);
+INSERT INTO t48 VALUES (48);
+CREATE TABLE t47 (a INT);
+INSERT INTO t47 VALUES (47);
+CREATE TABLE t46 (a INT);
+INSERT INTO t46 VALUES (46);
+CREATE TABLE t45 (a INT);
+INSERT INTO t45 VALUES (45);
+CREATE TABLE t44 (a INT);
+INSERT INTO t44 VALUES (44);
+CREATE TABLE t43 (a INT);
+INSERT INTO t43 VALUES (43);
+CREATE TABLE t42 (a INT);
+INSERT INTO t42 VALUES (42);
+CREATE TABLE t41 (a INT);
+INSERT INTO t41 VALUES (41);
+CREATE TABLE t40 (a INT);
+INSERT INTO t40 VALUES (40);
+CREATE TABLE t39 (a INT);
+INSERT INTO t39 VALUES (39);
+CREATE TABLE t38 (a INT);
+INSERT INTO t38 VALUES (38);
+CREATE TABLE t37 (a INT);
+INSERT INTO t37 VALUES (37);
+CREATE TABLE t36 (a INT);
+INSERT INTO t36 VALUES (36);
+CREATE TABLE t35 (a INT);
+INSERT INTO t35 VALUES (35);
+CREATE TABLE t34 (a INT);
+INSERT INTO t34 VALUES (34);
+CREATE TABLE t33 (a INT);
+INSERT INTO t33 VALUES (33);
+CREATE TABLE t32 (a INT);
+INSERT INTO t32 VALUES (32);
+CREATE TABLE t31 (a INT);
+INSERT INTO t31 VALUES (31);
+CREATE TABLE t30 (a INT);
+INSERT INTO t30 VALUES (30);
+CREATE TABLE t29 (a INT);
+INSERT INTO t29 VALUES (29);
+CREATE TABLE t28 (a INT);
+INSERT INTO t28 VALUES (28);
+CREATE TABLE t27 (a INT);
+INSERT INTO t27 VALUES (27);
+CREATE TABLE t26 (a INT);
+INSERT INTO t26 VALUES (26);
+CREATE TABLE t25 (a INT);
+INSERT INTO t25 VALUES (25);
+CREATE TABLE t24 (a INT);
+INSERT INTO t24 VALUES (24);
+CREATE TABLE t23 (a INT);
+INSERT INTO t23 VALUES (23);
+CREATE TABLE t22 (a INT);
+INSERT INTO t22 VALUES (22);
+CREATE TABLE t21 (a INT);
+INSERT INTO t21 VALUES (21);
+CREATE TABLE t20 (a INT);
+INSERT INTO t20 VALUES (20);
+CREATE TABLE t19 (a INT);
+INSERT INTO t19 VALUES (19);
+CREATE TABLE t18 (a INT);
+INSERT INTO t18 VALUES (18);
+CREATE TABLE t17 (a INT);
+INSERT INTO t17 VALUES (17);
+CREATE TABLE t16 (a INT);
+INSERT INTO t16 VALUES (16);
+CREATE TABLE t15 (a INT);
+INSERT INTO t15 VALUES (15);
+CREATE TABLE t14 (a INT);
+INSERT INTO t14 VALUES (14);
+CREATE TABLE t13 (a INT);
+INSERT INTO t13 VALUES (13);
+CREATE TABLE t12 (a INT);
+INSERT INTO t12 VALUES (12);
+CREATE TABLE t11 (a INT);
+INSERT INTO t11 VALUES (11);
+CREATE TABLE t10 (a INT);
+INSERT INTO t10 VALUES (10);
+CREATE TABLE t9 (a INT);
+INSERT INTO t9 VALUES (9);
+CREATE TABLE t8 (a INT);
+INSERT INTO t8 VALUES (8);
+CREATE TABLE t7 (a INT);
+INSERT INTO t7 VALUES (7);
+CREATE TABLE t6 (a INT);
+INSERT INTO t6 VALUES (6);
+CREATE TABLE t5 (a INT);
+INSERT INTO t5 VALUES (5);
+CREATE TABLE t4 (a INT);
+INSERT INTO t4 VALUES (4);
+CREATE TABLE t3 (a INT);
+INSERT INTO t3 VALUES (3);
+CREATE TABLE t2 (a INT);
+INSERT INTO t2 VALUES (2);
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1);
+CREATE TABLE t0 (a INT) ENGINE=MERGE UNION(t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11,t12,t13,t14,t15,t16,t17,t18,t19,t20,t21,t22,t23,t24,t25,t26,t27,t28,t29,t30,t31,t32,t33,t34,t35,t36,t37,t38,t39,t40,t41,t42,t43,t44,t45,t46,t47,t48,t49,t50,t51,t52,t53,t54,t55,t56,t57,t58,t59,t60,t61,t62,t63,t64,t65,t66,t67,t68,t69,t70,t71,t72,t73,t74,t75,t76,t77,t78,t79,t80,t81,t82,t83,t84,t85,t86,t87,t88,t89,t90,t91,t92,t93,t94,t95,t96,t97,t98,t99,t100,t101,t102,t103,t104,t105,t106,t107,t108,t109,t110,t111,t112,t113,t114,t115,t116,t117,t118,t119,t120,t121,t122,t123,t124,t125,t126,t127,t128,t129,t130,t131,t132,t133,t134,t135,t136,t137,t138,t139,t140,t141,t142,t143,t144,t145,t146,t147,t148,t149,t150,t151,t152,t153,t154,t155,t156,t157,t158,t159,t160,t161,t162,t163,t164,t165,t166,t167,t168,t169,t170,t171,t172,t173,t174,t175,t176,t177,t178,t179,t180,t181,t182,t183,t184,t185,t186,t187,t188,t189,t190,t191,t192,t193,t194,t195,t196,t197,t198,t199,t200,t201,t202,t203,t204,t205,t206,t207,t208,t209,t210,t211,t212,t213,t214,t215,t216,t217,t218,t219,t220,t221,t222,t223,t224,t225,t226,t227,t228,t229,t230,t231,t232,t233,t234,t235,t236,t237,t238,t239,t240,t241,t242,t243,t244,t245,t246,t247,t248,t249,t250,t251,t252,t253,t254,t255);
+SET GLOBAL query_cache_size = 1048576;
+FLUSH STATUS;
+SELECT a FROM t0 WHERE a = 1;
+a
+1
+SHOW STATUS LIKE "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+TRUNCATE TABLE t255;
+SELECT a FROM t1;
+a
+1
+TRUNCATE TABLE t254;
+SELECT a FROM t2;
+a
+2
+TRUNCATE TABLE t253;
+SELECT a FROM t3;
+a
+3
+TRUNCATE TABLE t252;
+SELECT a FROM t4;
+a
+4
+TRUNCATE TABLE t251;
+SELECT a FROM t5;
+a
+5
+TRUNCATE TABLE t250;
+SELECT a FROM t6;
+a
+6
+TRUNCATE TABLE t249;
+SELECT a FROM t7;
+a
+7
+TRUNCATE TABLE t248;
+SELECT a FROM t8;
+a
+8
+TRUNCATE TABLE t247;
+SELECT a FROM t9;
+a
+9
+TRUNCATE TABLE t246;
+SELECT a FROM t10;
+a
+10
+TRUNCATE TABLE t245;
+SELECT a FROM t11;
+a
+11
+TRUNCATE TABLE t244;
+SELECT a FROM t12;
+a
+12
+TRUNCATE TABLE t243;
+SELECT a FROM t13;
+a
+13
+TRUNCATE TABLE t242;
+SELECT a FROM t14;
+a
+14
+TRUNCATE TABLE t241;
+SELECT a FROM t15;
+a
+15
+TRUNCATE TABLE t240;
+SELECT a FROM t16;
+a
+16
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+DROP TABLE t11;
+DROP TABLE t10;
+DROP TABLE t9;
+DROP TABLE t8;
+DROP TABLE t7;
+DROP TABLE t6;
+DROP TABLE t5;
+DROP TABLE t4;
+DROP TABLE t3;
+DROP TABLE t2;
+DROP TABLE t1;
+SET @@global.query_cache_size = 0;
+SET @@global.table_definition_cache = @save_table_definition_cache;
+End of 5.1 tests

mysql-test/t/query_cache_merge.test

@@ -48,3 +48,61 @@ SET @@global.query_cache_size=0;
 set @@global.table_definition_cache=@save_table_definition_cache;
 
 # End of 4.1 tests
+
+#
+# Bug#33362: Query cache invalidation (truncate) may hang if cached query uses many tables
+#
+
+SET @save_table_definition_cache = @@global.table_definition_cache;
+SET @@global.table_definition_cache = 512;
+
+let $c= 255;
+
+while ($c)
+{
+  eval CREATE TABLE t$c (a INT);
+  eval INSERT INTO t$c VALUES ($c);
+  dec $c;
+}
+
+let $c= 254;
+let $str= t255;
+
+while ($c)
+{
+  let $str= t$c,$str;
+  dec $c;
+}
+
+eval CREATE TABLE t0 (a INT) ENGINE=MERGE UNION($str);
+SET GLOBAL query_cache_size = 1048576;
+FLUSH STATUS;
+SELECT a FROM t0 WHERE a = 1;
+SHOW STATUS LIKE "Qcache_queries_in_cache";
+
+let $c= 255;
+let $i= 1;
+
+while ($c)
+{
+  eval TRUNCATE TABLE t$c;
+  eval SELECT a FROM t$i;
+  dec $c;
+  inc $i;
+}
+
+SELECT a FROM t0;
+DROP TABLE t0;
+
+let $c= 255;
+
+while ($c)
+{
+  eval DROP TABLE t$c;
+  dec $c;
+}
+
+SET @@global.query_cache_size = 0;
+SET @@global.table_definition_cache = @save_table_definition_cache;
+
+--echo End of 5.1 tests

sql/sql_cache.cc

@@ -2746,7 +2746,7 @@ my_bool Query_cache::register_all_tables(Query_cache_block *block,
 	 tmp++)
       unlink_table(tmp);
   }
-  return (n);
+  return test(n);
 }