handlerton::discover_table_existence() method

sql/handler.cc

@@ -383,6 +383,11 @@ static int ha_finish_errors(void)
   return 0;
 }
 
+volatile int32 need_full_discover_for_existence= 0;
+static int full_discover_for_existence(handlerton *, const char *, const char *)
+{ return 1; }
+static int ext_based_existence(handlerton *, const char *, const char *)
+{ return 1; }
 
 int ha_finalize_handlerton(st_plugin_int *plugin)
 {
@@ -433,6 +438,9 @@ int ha_finalize_handlerton(st_plugin_int *plugin)
     hton2plugin[hton->slot]= NULL;
   }
 
+  if (hton->discover_table_existence == full_discover_for_existence)
+    my_atomic_add32(&need_full_discover_for_existence, -1);
+
   if (hton->discover_table_names)
     my_atomic_add32(&engines_with_discover_table_names, -1);
 
@@ -486,6 +494,18 @@ int ha_initialize_handlerton(st_plugin_int *plugin)
       hton->discover && hton->tablefile_extensions[0])
     hton->discover_table_names= hton_ext_based_table_discovery;
 
+  // default discover_table_existence implementation
+  if (!hton->discover_table_existence && hton->discover)
+  {
+    if (hton->tablefile_extensions[0])
+      hton->discover_table_existence= ext_based_existence;
+    else
+    {
+      hton->discover_table_existence= full_discover_for_existence;
+      my_atomic_add32(&need_full_discover_for_existence, 1);
+    }
+  }
+
   /*
     the switch below and hton->state should be removed when
     command-line options for plugins will be implemented
@@ -4377,6 +4397,83 @@ int ha_discover(THD *thd, const char *db, const char *name,
   DBUG_RETURN(error);
 }
 
+/**
+  Check if a given table exists, without doing a full discover, if possible
+*/
+
+static my_bool file_ext_exists(char *path, size_t path_len, const char *ext)
+{
+  strmake(path + path_len, ext, FN_REFLEN - path_len);
+  return !access(path, F_OK);
+}
+
+struct st_discover_existence_args
+{
+  char *path;
+  size_t  path_len;
+  const char *db, *table_name;
+};
+
+static my_bool discover_existence(THD *thd, plugin_ref plugin,
+                                  void *arg)
+{
+  st_discover_existence_args *args= (st_discover_existence_args*)arg;
+  handlerton *ht= plugin_data(plugin, handlerton *);
+  if (ht->state != SHOW_OPTION_YES || !ht->discover_table_existence)
+    return FALSE;
+
+  if (ht->discover_table_existence == ext_based_existence)
+    return file_ext_exists(args->path, args->path_len,
+                           ht->tablefile_extensions[0]);
+
+  return ht->discover_table_existence(ht, args->db, args->table_name);
+}
+
+bool ha_table_exists(THD *thd, const char *db, const char *table_name)
+{
+  DBUG_ENTER("ha_discover_table_existence");
+
+  if (need_full_discover_for_existence)
+  {
+    enum open_frm_error err;
+    TABLE_LIST table;
+
+    DBUG_ASSERT(0);
+    TABLE_SHARE *share= get_table_share(thd, db, table_name,
+                                        FRM_READ_TABLE_ONLY, &err);
+
+    if (share)
+    {
+      mysql_mutex_lock(&LOCK_open);
+      release_table_share(share);
+      mysql_mutex_unlock(&LOCK_open);
+      DBUG_RETURN(TRUE);
+    }
+    DBUG_RETURN(FALSE);
+  }
+
+  mysql_mutex_lock(&LOCK_open);
+  TABLE_SHARE *share= get_cached_table_share(db, table_name);
+  mysql_mutex_unlock(&LOCK_open);
+
+  if (share)
+    DBUG_RETURN(TRUE);
+
+  char path[FN_REFLEN + 1];
+  size_t path_len = build_table_filename(path, sizeof(path) - 1,
+                                         db, table_name, "", 0);
+
+  if (file_ext_exists(path, path_len, reg_ext))
+    DBUG_RETURN(TRUE);
+
+  st_discover_existence_args args= {path, path_len, db, table_name};
+
+  if (plugin_foreach(thd, discover_existence, MYSQL_STORAGE_ENGINE_PLUGIN,
+                     &args))
+    DBUG_RETURN(TRUE);
+
+  DBUG_RETURN(FALSE);
+}
 
 /**
   Discover all table names in a given database

sql/handler.h

@@ -1136,6 +1136,27 @@ struct handlerton
    */
    int (*discover_table_names)(handlerton *hton, LEX_STRING *db, MY_DIR *dir,
                                discovered_list *result);
+
+   /*
+     This is a method that allows to server to check if a table exists without
+     an overhead of the complete discovery.
+
+     By default (if not implemented by the engine, but the discovery_table() is
+     implemented) it will try to perform a file-based discovery:
+
+     - if tablefile_extensions[0] is not null this will look for a file name
+       with the tablefile_extensions[0] extension.
+
+     - if tablefile_extensions[0] is null, this will resort to discover_table().
+
+     Note that resorting to discover_table() is slow and the engine
+     should probably implement its own discover_table_existence() method,
+     if its tablefile_extensions[0] is null.
+
+     Returns 1 if the table exists and 0 if it does not.
+   */
+   int (*discover_table_existence)(handlerton *hton, const char *db,
+                                   const char *table_name);
 };
 
 
@@ -3072,6 +3093,8 @@ int ha_discover(THD* thd, const char* dbname, const char* name,
                 uchar** frmblob, size_t* frmlen);
 int ha_discover_table_names(THD *thd, LEX_STRING *db, MY_DIR *dirp,
                             handlerton::discovered_list *result);
+bool ha_table_exists(THD *thd, const char *db, const char *table_name);
+
 #ifdef MYSQL_SERVER
 extern volatile int32 engines_with_discover_table_names;
 #endif

sql/sql_base.cc

@@ -771,7 +771,7 @@ void release_table_share(TABLE_SHARE *share)
     #  TABLE_SHARE for table
 */
 
-static TABLE_SHARE *get_cached_table_share(const char *db, const char *table_name)
+TABLE_SHARE *get_cached_table_share(const char *db, const char *table_name)
 {
   char key[SAFE_NAME_LEN*2+2];
   uint key_length;
@@ -2337,58 +2337,6 @@ void drop_open_table(THD *thd, TABLE *table, const char *db_name,
 }
 
 
-/**
-    Check that table exists in table definition cache, on disk
-    or in some storage engine.
-
-    @param       thd        Thread context
-    @param       db         database name
-    @param       table_name table name
-    @param       path       (optional) path to the frm file
-
-    @note This function acquires LOCK_open internally.
-
-    @note If there is no .FRM file for the table but it exists in one
-          of engines (e.g. it was created on another node of NDB cluster)
-          this function will fetch and create proper .FRM file for it.
-
-    @retval  TRUE   Some error occurred
-    @retval  FALSE  No error. 'exists' out parameter set accordingly.
-*/
-
-bool table_exists(THD *thd, const char *db, const char *table_name,
-                  const char *path)
-{
-  char path_buf[FN_REFLEN + 1];
-  TABLE_SHARE *share;
-  DBUG_ENTER("table_exists");
-
-  mysql_mutex_lock(&LOCK_open);
-  share= get_cached_table_share(db, table_name);
-  mysql_mutex_unlock(&LOCK_open);
-
-  if (share)
-    DBUG_RETURN(TRUE);
-
-  if (!path)
-  {
-    build_table_filename(path_buf, sizeof(path_buf) - 1,
-                         db, table_name, reg_ext, 0);
-    path= path_buf;
-  }
-
-  if (!access(path, F_OK))
-    DBUG_RETURN(TRUE);
-
-  /* .FRM file doesn't exist. Try to discover it */
-  uchar *frmblob= NULL;
-  size_t frmlen;
-  bool exists= ! ha_discover(thd, db, table_name, &frmblob, &frmlen);
-  my_free(frmblob);
-  DBUG_RETURN(exists);
-}
-
-
 /**
   An error handler which converts, if possible, ER_LOCK_DEADLOCK error
   that can occur when we are trying to acquire a metadata lock to
@@ -2926,7 +2874,7 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
 
   if (table_list->open_strategy == TABLE_LIST::OPEN_IF_EXISTS)
   {
-    if (!table_exists(thd, table_list))
+    if (!ha_table_exists(thd, table_list->db, table_list->table_name))
       DBUG_RETURN(FALSE);
 
     /* Table exists. Let us try to open it. */
@@ -4705,7 +4653,7 @@ lock_table_names(THD *thd,
       We come here in the case of lock timeout when executing CREATE TABLE.
       Verify that table does exist (it usually does, as we got a lock conflict)
     */
-    if (table_exists(thd, tables_start))
+    if (ha_table_exists(thd, tables_start->db, tables_start->table_name))
     {
       if (thd->lex->create_info.options & HA_LEX_CREATE_IF_NOT_EXISTS)
       {

sql/sql_base.h

@@ -113,7 +113,7 @@ TABLE_SHARE *get_table_share(THD *thd, const char *db, const char *table_name,
                              enum open_frm_error *error,
                              my_hash_value_type hash_value);
 void release_table_share(TABLE_SHARE *share);
-
+TABLE_SHARE *get_cached_table_share(const char *db, const char *table_name);
 
 // convenience helper: call get_table_share() without precomputed hash_value
 static inline TABLE_SHARE *get_table_share(THD *thd, const char *db,
@@ -369,13 +369,6 @@ TABLE *find_table_for_mdl_upgrade(THD *thd, const char *db,
                                   bool no_error);
 void mark_tmp_table_for_reuse(TABLE *table);
 
-bool table_exists(THD *thd, const char *db, const char *table_name,
-                  const char *path);
-static inline bool table_exists(THD *thd, TABLE_LIST *table)
-{
-  return table_exists(thd, table->db, table->table_name, NULL);
-}
-
 int update_virtual_fields(THD *thd, TABLE *table,
       enum enum_vcol_update_mode vcol_update_mode= VCOL_UPDATE_FOR_READ);
 int dynamic_column_error_message(enum_dyncol_func_result rc);

sql/sql_db.cc

@@ -937,7 +937,7 @@ update_binlog:
       char quoted_name[FN_REFLEN+3];
 
       // Only write drop table to the binlog for tables that no longer exist.
-      if (table_exists(thd, tbl))
+      if (ha_table_exists(thd, tbl->db, tbl->table_name))
         continue;
 
       my_snprintf(quoted_name, sizeof(quoted_name), "%`s", tbl->table_name);

sql/sql_table.cc

@@ -2279,8 +2279,9 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
     }
     DEBUG_SYNC(thd, "rm_table_no_locks_before_delete_table");
     error= 0;
-    if (drop_temporary || !table_exists(thd, db, alias, path) ||
+    if (!table->internal_tmp_table &&
-         (!drop_view && dd_frm_type(thd, path, &frm_db_type) != FRMTYPE_TABLE))
+        (drop_temporary || !ha_table_exists(thd, db, alias) ||
+         (!drop_view && dd_frm_type(thd, path, &frm_db_type) != FRMTYPE_TABLE)))
     {
       /*
         One of the following cases happened:
@@ -2288,6 +2289,10 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
           . "DROP" but table was not found on disk and table can't be
             created from engine.
           . ./sql/datadict.cc +32 /Alfranio - TODO: We need to test this.
+
+        Table->internal_tmp_table is set when one of the #sql-xxx files
+        was left in the datadir after a crash during ALTER TABLE.
+        See Bug#30152.
       */
       if (if_exists)
 	push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
@@ -4317,7 +4322,7 @@ bool mysql_create_table_no_lock(THD *thd,
 
   if (!internal_tmp_table && !(create_info->options & HA_LEX_CREATE_TMP_TABLE))
   {
-    if (table_exists(thd, db, table_name, path))
+    if (ha_table_exists(thd, db, table_name))
     {
       if (create_info->options & HA_LEX_CREATE_IF_NOT_EXISTS)
         goto warn;