MDEV-12459 post-review fixes

* IS_USER_TEMP_TABLE() was misleading, name didn't match the code
* list of temp tables was rescanned number_of_databases times
* some temporary tables were not shown (from nonexistent databases)
* some temporary tables were shown more than once (e.g. after self-joins)
* sys.table_exists() - avoid querying I_S twice
* fix handling of temporary MERGE tables - it's pointless to fully open
  them, they're not in thd->temporary_tables, so they simply fail to
  open and are skipped. Relax the assertion instead.

mysql-test/main/information_schema_temp_table.result

@@ -200,17 +200,34 @@ show index in t;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
 t	1	b	1	b	A	NULL	NULL	NULL	YES	BTREE			NO
 drop database mysqltest;
+use test;
+show full tables;
+Tables_in_test	Table_type
+tmp_innodb_in_test	TEMPORARY TABLE
+select * from tmp_innodb_in_test, tmp_innodb_in_test x;
+a	a
+show full tables;
+Tables_in_test	Table_type
+tmp_innodb_in_test	TEMPORARY TABLE
+drop temporary tables tmp_innodb_in_test;
+create temporary table foo.t1 (a int);
+select table_schema, table_name from information_schema.tables where table_type='temporary';
+table_schema	table_name
+foo	t1
+mysqltest	tmp_table
+mysqltest	t
+my_db	t_temp
+drop temporary table foo.t1;
 #
 # MDEV-28351 Assertion `this->file->children_attached' failed in ha_myisammrg::info
 #
-use test;
 CREATE TABLE t1 (a INT) ENGINE=MyISAM;
 insert into t1 values (1);
 CREATE TEMPORARY TABLE t2 (a INT) ENGINE=MERGE UNION=(t1);
 CREATE TABLE t3 (a INT) ENGINE=MERGE UNION=(t1);
 SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'test';
 TABLE_CATALOG	TABLE_SCHEMA	TABLE_NAME	TABLE_TYPE	ENGINE	VERSION	ROW_FORMAT	TABLE_ROWS	AVG_ROW_LENGTH	DATA_LENGTH	MAX_DATA_LENGTH	INDEX_LENGTH	DATA_FREE	AUTO_INCREMENT	CREATE_TIME	UPDATE_TIME	CHECK_TIME	TABLE_COLLATION	CHECKSUM	CREATE_OPTIONS	TABLE_COMMENT	MAX_INDEX_LENGTH	TEMPORARY
-def	test	tmp_innodb_in_test	TEMPORARY	InnoDB	10	Dynamic	0	0	X	X	X	X	NULL	X	X	NULL	latin1_swedish_ci	NULL			X	Y
-def	test	t3	BASE TABLE	MRG_MyISAM	10	Fixed	1	5	X	X	X	X	NULL	X	X	NULL	latin1_swedish_ci	NULL			X	N
 def	test	t1	BASE TABLE	MyISAM	10	Fixed	1	7	X	X	X	X	NULL	X	X	NULL	latin1_swedish_ci	NULL			X	N
+def	test	t2	TEMPORARY	MRG_MyISAM	10	Fixed	0	0	X	X	X	X	NULL	X	X	NULL	latin1_swedish_ci	NULL			X	Y
+def	test	t3	BASE TABLE	MRG_MyISAM	10	Fixed	1	5	X	X	X	X	NULL	X	X	NULL	latin1_swedish_ci	NULL			X	N
 DROP TABLE t1,t2,t3;

mysql-test/main/information_schema_temp_table.test

@@ -195,15 +195,27 @@ show index in t;
 
 # Cleanup
 drop database mysqltest;
+use test;
+
+# many instances of the table temp table:
+show full tables;
+select * from tmp_innodb_in_test, tmp_innodb_in_test x;
+show full tables;
+drop temporary tables tmp_innodb_in_test;
+
+# non-existent db
+create temporary table foo.t1 (a int); # yup, that works
+select table_schema, table_name from information_schema.tables where table_type='temporary';
+drop temporary table foo.t1;
 
 --echo #
 --echo # MDEV-28351 Assertion `this->file->children_attached' failed in ha_myisammrg::info
 --echo #
-use test;
 CREATE TABLE t1 (a INT) ENGINE=MyISAM;
 insert into t1 values (1);
 CREATE TEMPORARY TABLE t2 (a INT) ENGINE=MERGE UNION=(t1);
 CREATE TABLE t3 (a INT) ENGINE=MERGE UNION=(t1);
+--sorted_result
 --replace_column 10 X 11 X 12 X 13 X 15 X 16 X 22 X
 SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'test';
 DROP TABLE t1,t2,t3;

mysql-test/suite/engines/funcs/r/rpl_row_drop.result

@@ -6,6 +6,7 @@ CREATE TABLE t2 (a int);
 CREATE TEMPORARY TABLE t2 (a int, b int);
 SHOW TABLES;
 Tables_in_test
+t2
 t1
 t2
 connection slave;
@@ -28,6 +29,7 @@ connection master;
 CREATE TEMPORARY TABLE t2 (a int, b int);
 SHOW TABLES;
 Tables_in_test
+t2
 t1
 t2
 connection slave;

scripts/sys_schema/procedures/table_exists.sql

@@ -154,21 +154,18 @@ BEGIN
     DECLARE db_quoted VARCHAR(64);
     DECLARE table_quoted VARCHAR(64);
     DECLARE v_table_type VARCHAR(30) DEFAULT '';
-    DECLARE v_table_type_num INT;
     DECLARE CONTINUE HANDLER FOR 1050 SET v_error = TRUE;
     DECLARE CONTINUE HANDLER FOR 1146 SET v_error = TRUE;
 
     -- First check do we have multiple rows, what can happen if temporary table
     -- and/or sequence is shadowing base table for example.
     -- In such scenario return temporary.
-    SET v_table_type_num = (SELECT COUNT(TABLE_TYPE) FROM information_schema.TABLES WHERE
+    SET v_table_type = (SELECT GROUP_CONCAT(TABLE_TYPE) FROM information_schema.TABLES WHERE
                             TABLE_SCHEMA = in_db AND TABLE_NAME = in_table);
 
-    IF v_table_type_num > 1 THEN
+    IF v_table_type LIKE '%,%' THEN
         SET out_exists = 'TEMPORARY';
     ELSE
-        SET v_table_type = (SELECT TABLE_TYPE FROM information_schema.TABLES WHERE
-                                TABLE_SCHEMA = in_db AND TABLE_NAME = in_table);
         IF v_table_type is NULL
         THEN
             SET v_table_type='';

sql/sql_base.cc

@@ -4764,10 +4764,10 @@ bool open_tables(THD *thd, const DDL_options_st &options,
   {
     TABLE *tbl= tables->table;
 
+    /* Schema tables may not have a TABLE object here. */
     if (!tbl)
       continue;
 
-    /* Schema tables may not have a TABLE object here. */
     if (tbl->file->ha_table_flags() & HA_CAN_MULTISTEP_MERGE)
     {
       /* MERGE tables need to access parent and child TABLE_LISTs. */

sql/sql_show.cc

@@ -70,7 +70,6 @@
 
 #include "lex_symbol.h"
 #define KEYWORD_SIZE 64
-#define IS_USER_TEMP_TABLE(A) (A->tmp_table != NO_TMP_TABLE)
 
 extern SYMBOL symbols[];
 extern size_t symbols_length;
@@ -5310,30 +5309,12 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
     goto err;
   }
 
-  bzero((char*) &table_acl_check, sizeof(table_acl_check));
-
-  if (make_db_list(thd, &db_names, &plan->lookup_field_vals))
-    goto err;
-
   /* Use tmp_mem_root to allocate data for opened tables */
   init_alloc_root(PSI_INSTRUMENT_ME, &tmp_mem_root, SHOW_ALLOC_BLOCK_SIZE,
                   SHOW_ALLOC_BLOCK_SIZE, MY_THREAD_SPECIFIC);
 
-  for (size_t i=0; i < db_names.elements(); i++)
-  {
-    LEX_CSTRING *db_name= db_names.at(i);
-    DBUG_ASSERT(db_name->length <= NAME_LEN);
-#ifndef NO_EMBEDDED_ACCESS_CHECKS
-    if (!(check_access(thd, SELECT_ACL, db_name->str,
-                       &thd->col_access, NULL, 0, 1) ||
-          (!thd->col_access && check_grant_db(thd, db_name->str))) ||
-        sctx->master_access & (DB_ACLS | SHOW_DB_ACL) ||
-        acl_get_all3(sctx, db_name->str, 0))
-#endif
-    {
-      Dynamic_array<LEX_CSTRING*> table_names(PSI_INSTRUMENT_MEM);
-
-      /* Separate handling for session temporary tables from the backup state
+  /*
+    Separate handling for session temporary tables from the backup state
     for table IS.tables and SHOW TABLES commands.
   */
   if ((schema_table_idx == SCH_TABLES || schema_table_idx == SCH_TABLE_NAMES) &&
@@ -5341,24 +5322,26 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
   {
     All_tmp_tables_list::Iterator it(*open_tables_state_backup.temporary_tables);
     TMP_TABLE_SHARE *share_temp;
+    const char *lookup_db= plan->lookup_field_vals.db_value.str;
+    int (*cmp)(CHARSET_INFO *, const char *, const char *)=
+      plan->lookup_field_vals.wild_db_value
+      ? wild_case_compare : system_charset_info->coll->strcasecmp;
     while ((share_temp= it++))
     {
-          DBUG_ASSERT(IS_USER_TEMP_TABLE(share_temp));
-          if (my_strcasecmp(system_charset_info, db_name->str,
-                            share_temp->db.str))
+      if (lookup_db)
+      {
+        if (cmp(system_charset_info, share_temp->db.str, lookup_db))
           continue;
+      }
 
-          All_share_tables_list::Iterator it2(share_temp->all_tmp_tables);
-          while (TABLE *tmp_tbl= it2++)
-          {
+      TABLE *tmp_tbl= share_temp->all_tmp_tables.front();
       if (schema_table_idx == SCH_TABLE_NAMES)
       {
         LEX_CSTRING *table_name= &tmp_tbl->s->table_name;
         restore_record(table, s->default_values);
-              table->field[schema_table->idx_field1]->
-                store(db_name->str, db_name->length, system_charset_info);
-              table->field[schema_table->idx_field2]->
-                store(table_name->str, table_name->length,
+        table->field[1]->store(share_temp->db.str, share_temp->db.length,
+                               system_charset_info);
+        table->field[2]->store(table_name->str, table_name->length,
                                system_charset_info);
         if (tmp_tbl->s->table_type == TABLE_TYPE_SEQUENCE)
           table->field[3]->store(STRING_WITH_LEN("TEMPORARY SEQUENCE"),
@@ -5369,28 +5352,29 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
         schema_table_store_record(thd, table);
       }
       else /* SCH_TABLE */
-            {
-              if (tmp_tbl->file->ha_table_flags() & HA_CAN_MULTISTEP_MERGE)
-              {
-                /*
-                  MyISAM MERGE table. We have to to call open on it and its
-                  children
-                */
-                LEX_CSTRING table_name=
-                  { tmp_tbl->alias.ptr(), tmp_tbl->alias.length() };
-                if (fill_schema_table_by_open(thd, &tmp_mem_root, FALSE,
-                                              table, schema_table,
-                                              &tmp_tbl->s->db, &table_name,
-                                              &open_tables_state_backup,
-                                              0))
-                  goto err;
-              }
-              else
         process_i_s_table_temporary_tables(thd, table, tmp_tbl);
     }
   }
-        }
-      }
+
+  bzero((char*) &table_acl_check, sizeof(table_acl_check));
+
+  if (make_db_list(thd, &db_names, &plan->lookup_field_vals))
+    goto err;
+
+  for (size_t i=0; i < db_names.elements(); i++)
+  {
+    LEX_CSTRING *db_name= db_names.at(i);
+    DBUG_ASSERT(db_name->length <= NAME_LEN);
+#ifndef NO_EMBEDDED_ACCESS_CHECKS
+    if (!(check_access(thd, SELECT_ACL, db_name->str,
+                       &thd->col_access, NULL, 0, 1) ||
+          (!thd->col_access && check_grant_db(thd, db_name->str))) ||
+        sctx->master_access & (DB_ACLS | SHOW_DB_ACL) ||
+        acl_get_all3(sctx, db_name->str, 0))
+#endif
+    {
+      Dynamic_array<LEX_CSTRING*> table_names(PSI_INSTRUMENT_MEM);
+
       int res= make_table_name_list(thd, &table_names, lex,
                                     &plan->lookup_field_vals, db_name);
       if (unlikely(res == 2))   /* Not fatal error, continue */
@@ -5655,11 +5639,11 @@ static int get_schema_tables_record(THD *thd, TABLE_LIST *tables,
 
     if (share->tmp_table == SYSTEM_TMP_TABLE)
       table->field[3]->store(STRING_WITH_LEN("SYSTEM VIEW"), cs);
-    else if (IS_USER_TEMP_TABLE(share) && share->table_type == TABLE_TYPE_SEQUENCE)
+    else if (share->tmp_table && share->table_type == TABLE_TYPE_SEQUENCE)
       table->field[3]->store(STRING_WITH_LEN("TEMPORARY SEQUENCE"), cs);
     else if (share->table_type == TABLE_TYPE_SEQUENCE)
       table->field[3]->store(STRING_WITH_LEN("SEQUENCE"), cs);
-    else if (IS_USER_TEMP_TABLE(share))
+    else if (share->tmp_table)
       table->field[3]->store(STRING_WITH_LEN("TEMPORARY"), cs);
     else
     {

storage/myisammrg/ha_myisammrg.cc

@@ -1273,7 +1273,6 @@ int ha_myisammrg::delete_all_rows()
 int ha_myisammrg::info(uint flag)
 {
   MYMERGE_INFO mrg_info;
-  DBUG_ASSERT(this->file->children_attached);
   (void) myrg_status(file,&mrg_info,flag);
   /*
     The following fails if one has not compiled MySQL with -DBIG_TABLES

storage/myisammrg/myrg_info.c

@@ -44,6 +44,8 @@ int myrg_status(MYRG_INFO *info,register MYMERGE_INFO *x,int flag)
     MYRG_TABLE *file;
 
     info->records=info->del=info->data_file_length=0;
+    if (likely(info->children_attached))
+    {
       for (file=info->open_tables ; file != info->end_table ; file++)
       {
         file->file_offset=info->data_file_length;
@@ -53,11 +55,6 @@ int myrg_status(MYRG_INFO *info,register MYMERGE_INFO *x,int flag)
         DBUG_PRINT("info2",("table: %s, offset: %lu",
                     file->table->filename,(ulong) file->file_offset));
       }
-    x->records= info->records;
-    x->deleted= info->del;
-    x->data_file_length= info->data_file_length;
-    x->reclength= info->reclength;
-    x->options= info->options;
       if (current_table)
       {
         /*
@@ -80,6 +77,12 @@ int myrg_status(MYRG_INFO *info,register MYMERGE_INFO *x,int flag)
         x->errkey= 0;
         x->dupp_key_pos= 0;
       }
+    }
+    x->records= info->records;
+    x->deleted= info->del;
+    x->data_file_length= info->data_file_length;
+    x->reclength= info->reclength;
+    x->options= info->options;
     x->rec_per_key = info->rec_per_key_part;
   }
   DBUG_RETURN(0);