1 files changed, 85 insertions, 221 deletions

diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc
index 83013b8b1e7..b65f460c896 100644
--- a/sql/sql_statistics.cc
+++ b/sql/sql_statistics.cc
@@ -1,5 +1,5 @@
 /* Copyright (C) 2009 MySQL AB
-   Copyright (c) 2019, MariaDB Corporation.
+   Copyright (c) 2019, 2020, MariaDB Corporation.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -2214,27 +2214,13 @@ static int alloc_statistics_for_table_share(THD* thd, TABLE_SHARE *table_share)
 
   DBUG_ENTER("alloc_statistics_for_table_share");
 
-  DEBUG_SYNC(thd, "statistics_mem_alloc_start1");
-  DEBUG_SYNC(thd, "statistics_mem_alloc_start2");
-
-  mysql_mutex_lock(&table_share->LOCK_share);
-
-  if (stats_cb->stats_can_be_read)
-  {
-    mysql_mutex_unlock(&table_share->LOCK_share);
-    DBUG_RETURN(0);
-  }
-
   Table_statistics *table_stats= stats_cb->table_stats;
   if (!table_stats)
   {
     table_stats=  (Table_statistics *) alloc_root(&stats_cb->mem_root,
                                                   sizeof(Table_statistics));
     if (!table_stats)
-    {
-      mysql_mutex_unlock(&table_share->LOCK_share);
       DBUG_RETURN(1);
-    }
     memset(table_stats, 0, sizeof(Table_statistics));
     stats_cb->table_stats= table_stats;
   }
@@ -2300,89 +2286,11 @@ static int alloc_statistics_for_table_share(THD* thd, TABLE_SHARE *table_share)
       }
     }   
   }
-
-  if (column_stats && index_stats && idx_avg_frequency)
-    stats_cb->stats_can_be_read= TRUE;
-
-  mysql_mutex_unlock(&table_share->LOCK_share);
-
-  DBUG_RETURN(0);
+  DBUG_RETURN(column_stats && index_stats && idx_avg_frequency ? 0 : 1);
 }
 
 
 /**
-  @brief 
-  Allocate memory for the histogram used by a table share
-
-  @param
-  thd         Thread handler
-  @param
-  table_share Table share for which the memory for histogram data is allocated
-  @param
-  is_safe     TRUE <-> at any time only one thread can perform the function
-
-  @note
-  The function allocates the memory for the histogram built for a table in the
-  table's share memory with the intention to read the data there from the
-  system persistent statistical table mysql.column_stats,
-  The memory is allocated in the table_share's mem_root.
-  If the parameter is_safe is TRUE then it is guaranteed that at any given time
-  only one thread is executed the code of the function.
-
-  @retval
-  0     If the memory for all statistical data has been successfully allocated  
-  @retval
-  1     Otherwise
-
-  @note
-  Currently the function always is called with the parameter is_safe set
-  to FALSE. 
-*/      
-
-static
-int alloc_histograms_for_table_share(THD* thd, TABLE_SHARE *table_share, 
-                                     bool is_safe)
-{
-  TABLE_STATISTICS_CB *stats_cb= &table_share->stats_cb;
-
-  DBUG_ENTER("alloc_histograms_for_table_share");
-
-  if (!is_safe)
-    mysql_mutex_lock(&table_share->LOCK_share);
-
-  if (stats_cb->histograms_can_be_read)
-  {
-    if (!is_safe)
-      mysql_mutex_unlock(&table_share->LOCK_share);
-    DBUG_RETURN(0);
-  }
-
-  Table_statistics *table_stats= stats_cb->table_stats;
-  ulong total_hist_size= table_stats->total_hist_size;
-
-  if (total_hist_size && !table_stats->histograms)
-  {
-    uchar *histograms= (uchar *) alloc_root(&stats_cb->mem_root,
-                                            total_hist_size);
-    if (!histograms)
-    {
-      if (!is_safe)
-        mysql_mutex_unlock(&table_share->LOCK_share);
-      DBUG_RETURN(1);
-    }
-    memset(histograms, 0, total_hist_size);
-    table_stats->histograms= histograms;
-    stats_cb->histograms_can_be_read= TRUE;
-  }
-
-  if (!is_safe)
-    mysql_mutex_unlock(&table_share->LOCK_share);
-
-  DBUG_RETURN(0);
-
-}
-
-/**
   @brief
   Initialize the aggregation fields to collect statistics on a column
 
@@ -2923,15 +2831,26 @@ int read_statistics_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
   Field **field_ptr;
   KEY *key_info, *key_info_end;
   TABLE_SHARE *table_share= table->s;
-  Table_statistics *read_stats= table_share->stats_cb.table_stats;
   enum_check_fields old_check_level= thd->count_cuted_fields;
 
   DBUG_ENTER("read_statistics_for_table");
+  DEBUG_SYNC(thd, "statistics_mem_alloc_start1");
+  DEBUG_SYNC(thd, "statistics_mem_alloc_start2");
+
+  if (!table_share->stats_cb.start_stats_load())
+    DBUG_RETURN(table_share->stats_cb.stats_are_ready() ? 0 : 1);
+
+  if (alloc_statistics_for_table_share(thd, table_share))
+  {
+    table_share->stats_cb.abort_stats_load();
+    DBUG_RETURN(1);
+  }
 
   /* Don't write warnings for internal field conversions */
   thd->count_cuted_fields= CHECK_FIELD_IGNORE;
 
   /* Read statistics from the statistical table table_stats */
+  Table_statistics *read_stats= table_share->stats_cb.table_stats;
   stat_table= stat_tables[TABLE_STAT].table;
   Table_stat table_stat(stat_table, table);
   table_stat.set_key_fields();
@@ -2948,7 +2867,7 @@ int read_statistics_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
     column_stat.get_stat_values();
     total_hist_size+= table_field->read_stats->histogram.get_size();
   }
-  read_stats->total_hist_size= total_hist_size;
+  table_share->stats_cb.total_hist_size= total_hist_size;
 
   /* Read statistics from the statistical table index_stats */
   stat_table= stat_tables[INDEX_STAT].table;
@@ -3010,9 +2929,8 @@ int read_statistics_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
     }
   }
 
-  table->stats_is_read= TRUE;
   thd->count_cuted_fields= old_check_level;
-
+  table_share->stats_cb.end_stats_load();
   DBUG_RETURN(0);
 }
 
@@ -3052,71 +2970,6 @@ void delete_stat_values_for_table_share(TABLE_SHARE *table_share)
 
 /**
   @brief
-  Check whether any statistics is to be read for tables from a table list
-
-  @param
-  thd         The thread handle
-  @param
-  tables      The tables list for whose tables the check is to be done
-
-  @details
-  The function checks whether for any of the tables opened and locked for
-  a statement statistics from statistical tables is needed to be read.
-
-  @retval
-  TRUE        statistics for any of the tables is needed to be read 
-  @retval
-  FALSE       Otherwise
-*/
-
-static
-bool statistics_for_tables_is_needed(THD *thd, TABLE_LIST *tables)
-{
-  if (!tables)
-    return FALSE;
-
-  /* 
-    Do not read statistics for any query that explicity involves
-    statistical tables, failure to to do so we may end up
-    in a deadlock.
-  */
-
-  for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
-  {
-    if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
-    {
-      TABLE_SHARE *table_share= tl->table->s;
-      if (table_share && 
-          table_share->table_category != TABLE_CATEGORY_USER
-          && is_stat_table(&tl->db, &tl->alias))
-        return FALSE;
-    }
-  }
-
-  for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
-  {
-    if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
-    {
-      TABLE_SHARE *table_share= tl->table->s;
-      if (table_share && 
-          table_share->stats_cb.stats_can_be_read &&
-          (!table_share->stats_cb.stats_is_read ||
-           (!table_share->stats_cb.histograms_are_read &&
-            thd->variables.optimizer_use_condition_selectivity > 3)))
-        return TRUE;
-      if (table_share->stats_cb.stats_is_read)
-        tl->table->stats_is_read= TRUE;
-      if (table_share->stats_cb.histograms_are_read)
-        tl->table->histograms_are_read= TRUE;
-    } 
-  }
-
-  return FALSE;
-}
-
-
-/**
-  @brief
   Read histogram for a table from the persistent statistical tables
 
   @param
@@ -3150,26 +3003,25 @@ bool statistics_for_tables_is_needed(THD *thd, TABLE_LIST *tables)
 static
 int read_histograms_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
 {
-  TABLE_SHARE *table_share= table->s;
-  
+  TABLE_STATISTICS_CB *stats_cb= &table->s->stats_cb;
   DBUG_ENTER("read_histograms_for_table");
 
-  if (!table_share->stats_cb.histograms_can_be_read)
+  if (stats_cb->start_histograms_load())
   {
-    (void) alloc_histograms_for_table_share(thd, table_share, FALSE);
-  }
-  if (table_share->stats_cb.histograms_can_be_read &&
-      !table_share->stats_cb.histograms_are_read)
-  {
-    Field **field_ptr;
-    uchar *histogram= table_share->stats_cb.table_stats->histograms;
-    TABLE *stat_table= stat_tables[COLUMN_STAT].table;
-    Column_stat column_stat(stat_table, table);
-    for (field_ptr= table_share->field; *field_ptr; field_ptr++)
+    uchar *histogram= (uchar *) alloc_root(&stats_cb->mem_root,
+                                           stats_cb->total_hist_size);
+    if (!histogram)
+    {
+      stats_cb->abort_histograms_load();
+      DBUG_RETURN(1);
+    }
+    memset(histogram, 0, stats_cb->total_hist_size);
+
+    Column_stat column_stat(stat_tables[COLUMN_STAT].table, table);
+    for (Field **field_ptr= table->s->field; *field_ptr; field_ptr++)
     {
       Field *table_field= *field_ptr;
-      uint hist_size= table_field->read_stats->histogram.get_size();
-      if (hist_size)
+      if (uint hist_size= table_field->read_stats->histogram.get_size())
       {
         column_stat.set_key_fields(table_field);
         table_field->read_stats->histogram.set_values(histogram);
@@ -3177,8 +3029,9 @@ int read_histograms_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
         histogram+= hist_size;
       }
     }
+    stats_cb->end_histograms_load();
   }
- 
+  table->histograms_are_read= true;
   DBUG_RETURN(0);
 }
 
@@ -3226,6 +3079,23 @@ int read_statistics_for_tables_if_needed(THD *thd, TABLE_LIST *tables)
 }
 
 
+static void dump_stats_from_share_to_table(TABLE *table)
+{
+  TABLE_SHARE *table_share= table->s;
+  KEY *key_info= table_share->key_info;
+  KEY *key_info_end= key_info + table_share->keys;
+  KEY *table_key_info= table->key_info;
+  for ( ; key_info < key_info_end; key_info++, table_key_info++)
+    table_key_info->read_stats= key_info->read_stats;
+
+  Field **field_ptr= table_share->field;
+  Field **table_field_ptr= table->field;
+  for ( ; *field_ptr; field_ptr++, table_field_ptr++)
+    (*table_field_ptr)->read_stats= (*field_ptr)->read_stats;
+  table->stats_is_read= true;
+}
+
+
 int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
 {
   TABLE_LIST stat_tables[STATISTICS_TABLES];
@@ -3236,38 +3106,42 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
   if (thd->bootstrap || thd->variables.use_stat_tables == NEVER)
     DBUG_RETURN(0);
 
+  bool found_stat_table= false;
+  bool statistics_for_tables_is_needed= false;
+
   for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
   {
-    if (tl->table)
+    TABLE_SHARE *table_share;
+    if (!tl->is_view_or_derived() && tl->table && (table_share= tl->table->s) &&
+        table_share->tmp_table == NO_TMP_TABLE)
     {
-      TABLE_SHARE *table_share= tl->table->s;
-      if (table_share && table_share->table_category == TABLE_CATEGORY_USER &&
-          table_share->tmp_table == NO_TMP_TABLE)
+      if (table_share->table_category == TABLE_CATEGORY_USER)
       {
-        if (table_share->stats_cb.stats_can_be_read ||
-            !alloc_statistics_for_table_share(thd, table_share))
+        if (table_share->stats_cb.stats_are_ready())
         {
-          if (table_share->stats_cb.stats_can_be_read)
-          {
-            KEY *key_info= table_share->key_info;
-            KEY *key_info_end= key_info + table_share->keys;
-            KEY *table_key_info= tl->table->key_info;
-            for ( ; key_info < key_info_end; key_info++, table_key_info++)
-              table_key_info->read_stats= key_info->read_stats;
-            Field **field_ptr= table_share->field;
-            Field **table_field_ptr= tl->table->field;
-            for ( ; *field_ptr; field_ptr++, table_field_ptr++)
-              (*table_field_ptr)->read_stats= (*field_ptr)->read_stats;
-            tl->table->stats_is_read= table_share->stats_cb.stats_is_read;
-          }
+          if (!tl->table->stats_is_read)
+            dump_stats_from_share_to_table(tl->table);
+          tl->table->histograms_are_read=
+            table_share->stats_cb.histograms_are_ready();
+          if (table_share->stats_cb.histograms_are_ready() ||
+              thd->variables.optimizer_use_condition_selectivity <= 3)
+            continue;
         }
+        statistics_for_tables_is_needed= true;
       }
+      else if (is_stat_table(&tl->db, &tl->alias))
+        found_stat_table= true;
     }
   }
 
   DEBUG_SYNC(thd, "statistics_read_start");
 
-  if (!statistics_for_tables_is_needed(thd, tables))
+  /*
+    Do not read statistics for any query that explicity involves
+    statistical tables, failure to to do so we may end up
+    in a deadlock.
+  */
+  if (found_stat_table || !statistics_for_tables_is_needed)
     DBUG_RETURN(0);
 
   if (open_stat_tables(thd, stat_tables, &open_tables_backup, FALSE))
@@ -3275,32 +3149,22 @@ int read_statistics_for_tables(THD *thd, TABLE_LIST *tables)
 
   for (TABLE_LIST *tl= tables; tl; tl= tl->next_global)
   {
-    if (!tl->is_view_or_derived() && !is_temporary_table(tl) && tl->table)
-    { 
-      TABLE_SHARE *table_share= tl->table->s;
-      if (table_share && !(table_share->table_category == TABLE_CATEGORY_USER))
-        continue;
-
-      if (table_share && 
-          table_share->stats_cb.stats_can_be_read &&
-	  !table_share->stats_cb.stats_is_read)
+    TABLE_SHARE *table_share;
+    if (!tl->is_view_or_derived() && tl->table && (table_share= tl->table->s) &&
+        table_share->tmp_table == NO_TMP_TABLE &&
+        table_share->table_category == TABLE_CATEGORY_USER)
+    {
+      if (!tl->table->stats_is_read)
       {
-        (void) read_statistics_for_table(thd, tl->table, stat_tables);
-        table_share->stats_cb.stats_is_read= TRUE;
+        if (!read_statistics_for_table(thd, tl->table, stat_tables))
+          dump_stats_from_share_to_table(tl->table);
+        else
+          continue;
       }
-      if (table_share->stats_cb.stats_is_read)
-        tl->table->stats_is_read= TRUE;
-      if (thd->variables.optimizer_use_condition_selectivity > 3 && 
-          table_share && table_share->stats_cb.stats_can_be_read &&
-          !table_share->stats_cb.histograms_are_read)
-      {
+      if (thd->variables.optimizer_use_condition_selectivity > 3)
         (void) read_histograms_for_table(thd, tl->table, stat_tables);
-        table_share->stats_cb.histograms_are_read= TRUE;
-      }
-      if (table_share->stats_cb.histograms_are_read)
-        tl->table->histograms_are_read= TRUE;
     }
-  }  
+  }
 
   close_system_tables(thd, &open_tables_backup);