MDEV-31022: SIGSEGV in maria_create from create_internal_tmp_table

The code in create_internal_tmp_table() didn't take into account that
now temporary (derived) tables may have multiple indexes:

- one index due to duplicate removal
   = In this example created by conversion of big-IN(...) into subquery
   = this index might be converted into a "unique constraint" if the key
     length is too large.
- one index added by derived_with_keys optimization.

Make create_internal_tmp_table() handle multiple indexes.

Before this patch, use of a unique constraint was indicated in
TABLE_SHARE::uniques. This was ok as unique constraint was the only index
in the table. Now it's no longer the case so TABLE_SHARE::uniques is removed
and replaced with an in-memory-only flag HA_UNIQUE_HASH.

This patch is based on Monty's patch.
Co-Author: Monty <monty@mariadb.org>

Author: spetrunia

include/my_base.h

@@ -104,7 +104,8 @@ enum ha_key_alg {
   HA_KEY_ALG_RTREE=	2,		/* R-tree, for spatial searches */
   HA_KEY_ALG_HASH=	3,		/* HASH keys (HEAP tables) */
   HA_KEY_ALG_FULLTEXT=	4,		/* FULLTEXT (MyISAM tables) */
-  HA_KEY_ALG_LONG_HASH= 5		/* long BLOB keys */
+  HA_KEY_ALG_LONG_HASH= 5,		/* long BLOB keys */
+  HA_KEY_ALG_UNIQUE_HASH= 6		/* Internal UNIQUE hash (Aria) */
 };
 
         /* Storage media types */ 
@@ -276,11 +277,17 @@ enum ha_base_keytype {
 #define HA_SPATIAL		1024U   /* For spatial search */
 #define HA_NULL_ARE_EQUAL	2048U	/* NULL in key are cmp as equal */
 #define HA_GENERATED_KEY	8192U	/* Automatically generated key */
+/* 
+  Part of unique hash key. Used only for temporary (work) tables so is not
+  written to .frm files.
+*/
+#define HA_UNIQUE_HASH          262144U
 
         /* The combination of the above can be used for key type comparison. */
 #define HA_KEYFLAG_MASK (HA_NOSAME | HA_AUTO_KEY | \
                          HA_FULLTEXT | HA_UNIQUE_CHECK | \
-                         HA_SPATIAL | HA_NULL_ARE_EQUAL | HA_GENERATED_KEY)
+                         HA_SPATIAL | HA_NULL_ARE_EQUAL | HA_GENERATED_KEY | \
+                         HA_UNIQUE_HASH)
 
 /*
   Key contains partial segments.

mysql-test/main/derived.result

@@ -1499,5 +1499,33 @@ a
 2
 drop table t1;
 #
+# MDEV-31022: SIGSEGV in maria_create from create_internal_tmp_table
+# keydef incorrectly allocated on the stack in create_internal_tmp_table()
+#
+CREATE TABLE t1 (c CHAR(1) NULL) ENGINE=MyISAM;
+INSERT INTO t1 (c) VALUES (1);
+SET statement
+optimizer_where_cost=1,
+big_tables=1,
+in_predicate_conversion_threshold=2
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+c
+Warnings:
+Warning	1287	'@@big_tables' is deprecated and will be removed in a future release
+Warning	1287	'@@big_tables' is deprecated and will be removed in a future release
+SET statement
+optimizer_where_cost=1,
+big_tables=1,
+in_predicate_conversion_threshold=2,
+sql_mode=''
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+c
+Warnings:
+Warning	1287	'@@big_tables' is deprecated and will be removed in a future release
+Warning	1287	'@@big_tables' is deprecated and will be removed in a future release
+DROP TABLE t1;
+#
 # End of 11.0 tests
 #

mysql-test/main/derived.test

@@ -1273,6 +1273,30 @@ SET IN_PREDICATE_CONVERSION_THRESHOLD=100;
 SELECT a FROM t1 WHERE a IN ( 1, 1, 2, 194 );
 drop table t1;
 
+--echo #
+--echo # MDEV-31022: SIGSEGV in maria_create from create_internal_tmp_table
+--echo # keydef incorrectly allocated on the stack in create_internal_tmp_table()
+--echo #
+
+CREATE TABLE t1 (c CHAR(1) NULL) ENGINE=MyISAM;
+INSERT INTO t1 (c) VALUES (1);
+SET statement
+  optimizer_where_cost=1,
+  big_tables=1,
+  in_predicate_conversion_threshold=2
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+
+SET statement
+  optimizer_where_cost=1,
+  big_tables=1,
+  in_predicate_conversion_threshold=2,
+  sql_mode=''
+FOR
+SELECT * FROM t1 WHERE c IN ('','');
+
+DROP TABLE t1;
+
 --echo #
 --echo # End of 11.0 tests
 --echo #

sql/item_subselect.cc

@@ -5266,7 +5266,7 @@ bool subselect_hash_sj_engine::init(List<Item> *tmp_columns, uint subquery_id)
     //fprintf(stderr, "Q: %s\n", current_thd->query());
     DBUG_ASSERT(0);
     DBUG_ASSERT(
-      tmp_table->s->uniques ||
+      (tmp_table->key_info->flags & HA_UNIQUE_HASH) ||
       tmp_table->key_info->key_length >= tmp_table->file->max_key_length() ||
       tmp_table->key_info->user_defined_key_parts >
       tmp_table->file->max_key_parts());

sql/opt_subselect.cc

@@ -4903,11 +4903,13 @@ SJ_TMP_TABLE::create_sj_weedout_tmp_table(THD *thd)
   {
     DBUG_PRINT("info",("Creating group key in temporary table"));
     share->keys=1;
-    share->uniques= MY_TEST(using_unique_constraint);
     table->key_info= share->key_info= keyinfo;
     keyinfo->key_part=key_part_info;
-    keyinfo->flags=HA_NOSAME;
+    keyinfo->flags= HA_NOSAME | (using_unique_constraint ? HA_UNIQUE_HASH : 0);
+    keyinfo->ext_key_flags= keyinfo->flags;
     keyinfo->usable_key_parts= keyinfo->user_defined_key_parts= 1;
+    keyinfo->ext_key_parts= 1;
+    share->key_parts= 1;
     keyinfo->key_length=0;
     keyinfo->rec_per_key=0;
     keyinfo->algorithm= HA_KEY_ALG_UNDEF;