Many files:

  Fix Bug #1942: do not retrieve all columns in a table if we only need the 'ref' of the row (usually, the PRIMARY KEY) to calculate an ORDER BY

include/my_base.h

@@ -131,10 +131,14 @@ enum ha_extra_function {
   HA_EXTRA_IGNORE_DUP_KEY,		/* Dup keys don't rollback everything*/
   HA_EXTRA_NO_IGNORE_DUP_KEY,
   /*
-    Instructs InnoDB to retrieve all columns, not just those where
-    field->query_id is the same as the current query id
+    Instructs InnoDB to retrieve all columns (except in key read), not just
+    those where field->query_id is the same as the current query id
   */
   HA_EXTRA_RETRIEVE_ALL_COLS,
+  /*
+    Instructs InnoDB to retrieve at least all the primary key columns
+  */
+  HA_EXTRA_RETRIEVE_PRIMARY_KEY,
   HA_EXTRA_PREPARE_FOR_DELETE,
   HA_EXTRA_PREPARE_FOR_UPDATE,		/* Remove read cache if problems */
   HA_EXTRA_PRELOAD_BUFFER_SIZE          /* Set buffer size for preloading */

innobase/dict/dict0dict.c

@@ -631,7 +631,7 @@ dict_table_get_on_id(
 }
 
 /************************************************************************
-Looks for column n postion in the clustered index. */
+Looks for column n position in the clustered index. */
 
 ulint
 dict_table_get_nth_col_pos(
@@ -645,6 +645,44 @@ dict_table_get_nth_col_pos(
 								n));
 }
 
+/************************************************************************
+Checks if a column is in the ordering columns of the clustered index of a
+table. Column prefixes are treated like whole columns. */
+
+ibool
+dict_table_col_in_clustered_key(
+/*============================*/
+				/* out: TRUE if the column, or its prefix, is
+				in the clustered key */
+	dict_table_t*	table,	/* in: table */
+	ulint		n)	/* in: column number */
+{
+	dict_index_t*	index;
+	dict_field_t*	field;
+	dict_col_t*	col;
+	ulint		pos;
+	ulint		n_fields;
+	
+	ut_ad(table);
+
+	col = dict_table_get_nth_col(table, n);
+
+	index = dict_table_get_first_index(table);
+
+	n_fields = dict_index_get_n_unique(index);
+	
+	for (pos = 0; pos < n_fields; pos++) {
+		field = dict_index_get_nth_field(index, pos);
+
+		if (col == field->col) {
+
+			return(TRUE);
+		}
+	}
+
+	return(FALSE);
+}
+
 /**************************************************************************
 Inits the data dictionary module. */
 

innobase/include/dict0dict.h

@@ -493,6 +493,17 @@ dict_table_get_sys_col_no(
 				/* out: column number */
 	dict_table_t*	table,	/* in: table */
 	ulint		sys);	/* in: DATA_ROW_ID, ... */
+/************************************************************************
+Checks if a column is in the ordering columns of the clustered index of a
+table. Column prefixes are treated like whole columns. */
+
+ibool
+dict_table_col_in_clustered_key(
+/*============================*/
+				/* out: TRUE if the column, or its prefix, is
+				in the clustered key */
+	dict_table_t*	table,	/* in: table */
+	ulint		n);	/* in: column number */
 /***********************************************************************
 Copies types of columns contained in table to tuple. */
 

innobase/include/row0mysql.h

@@ -510,13 +510,15 @@ struct row_prebuilt_struct {
 	byte*		ins_upd_rec_buff;/* buffer for storing data converted
 					to the Innobase format from the MySQL
 					format */
-	ibool		hint_no_need_to_fetch_extra_cols;
-					/* normally this is TRUE, but
-					MySQL will set this to FALSE
-					if we might be required to fetch also
-					other columns than mentioned in the
-					query: the clustered index column(s),
-					or an auto-increment column*/
+	ulint		hint_need_to_fetch_extra_cols;
+					/* normally this is set to 0; if this
+					is set to ROW_RETRIEVE_PRIMARY_KEY,
+					then we should at least retrieve all
+					columns in the primary key; if this
+					is set to ROW_RETRIEVE_ALL_COLS, then
+					we must retrieve all columns in the
+					key (if read_just_key == 1), or all
+					columns in the table */
 	upd_node_t*	upd_node;	/* Innobase SQL update node used
 					to perform updates and deletes */
 	que_fork_t*	ins_graph;	/* Innobase SQL query graph used
@@ -572,6 +574,11 @@ struct row_prebuilt_struct {
 #define ROW_MYSQL_DUMMY_TEMPLATE 3	/* dummy template used in
 					row_scan_and_check_index */
 
+/* Values for hint_need_to_fetch_extra_cols */
+#define ROW_RETRIEVE_PRIMARY_KEY	1
+#define ROW_RETRIEVE_ALL_COLS		2
+
+
 #ifndef UNIV_NONINL
 #include "row0mysql.ic"
 #endif

sql/ha_innodb.cc

@@ -702,7 +702,7 @@ ha_innobase::init_table_handle_for_HANDLER(void)
 
         /* Always fetch all columns in the index record */
 
-        prebuilt->hint_no_need_to_fetch_extra_cols = FALSE;
+        prebuilt->hint_need_to_fetch_extra_cols = ROW_RETRIEVE_ALL_COLS;
 
         /* We want always to fetch all columns in the whole row? Or do
 	we???? */
@@ -1951,6 +1951,7 @@ build_template(
 	ulint		n_fields;
 	ulint		n_requested_fields	= 0;
 	ibool		fetch_all_in_key	= FALSE;
+	ibool		fetch_primary_key_cols	= FALSE;
 	ulint		i;
 
 	if (prebuilt->select_lock_type == LOCK_X) {
@@ -1961,8 +1962,9 @@ build_template(
 	        templ_type = ROW_MYSQL_WHOLE_ROW;
 	}
 
-	if (templ_type == ROW_MYSQL_REC_FIELDS
-	    && !prebuilt->hint_no_need_to_fetch_extra_cols) {
+	if (templ_type == ROW_MYSQL_REC_FIELDS) {
+	     if (prebuilt->hint_need_to_fetch_extra_cols
+						== ROW_RETRIEVE_ALL_COLS) {
 
 		/* We know we must at least fetch all columns in the key, or
 		all columns in the table */
@@ -1977,15 +1979,14 @@ build_template(
 
 			fetch_all_in_key = TRUE;
 		} else {
-			/* We are building a temporary table: fetch all
- 			columns; the reason is that MySQL may use the
-			clustered index key to store rows, but the mechanism
-			we use below to detect required columns does not
-			reveal that. Actually, it might be enough to
-			fetch only all in the key also in this case! */
-
 			templ_type = ROW_MYSQL_WHOLE_ROW;
 		}
+	    } else if (prebuilt->hint_need_to_fetch_extra_cols
+						== ROW_RETRIEVE_PRIMARY_KEY) {
+		/* We must at least fetch all primary key cols */
+
+		fetch_primary_key_cols = TRUE;
+	    }
 	}
 
 	clust_index = dict_table_get_first_index_noninline(prebuilt->table);
@@ -2004,7 +2005,7 @@ build_template(
 		the clustered index */
 	}
 
-	n_fields = (ulint)table->fields;
+	n_fields = (ulint)table->fields; /* number of columns */
 
 	if (!prebuilt->mysql_template) {
 		prebuilt->mysql_template = (mysql_row_templ_t*)
@@ -2017,6 +2018,8 @@ build_template(
 
 	prebuilt->templ_contains_blob = FALSE;
 
+	/* Note that in InnoDB, i is the column number. MySQL calls columns
+	'fields'. */
 	for (i = 0; i < n_fields; i++) {
 		templ = prebuilt->mysql_template + n_requested_fields;
 		field = table->field[i];
@@ -2029,6 +2032,8 @@ build_template(
 		if (templ_type == ROW_MYSQL_REC_FIELDS
 		    && !(fetch_all_in_key
 			 && dict_index_contains_col_or_prefix(index, i))
+		    && !(fetch_primary_key_cols
+			 && dict_table_col_in_clustered_key(index->table, i))
 		    && thd->query_id != field->query_id) {
 
 			/* This field is not needed in the query, skip it */
@@ -4514,7 +4519,14 @@ ha_innobase::extra(
     			prebuilt->read_just_key = 0;
     			break;
 	        case HA_EXTRA_RETRIEVE_ALL_COLS:
-			prebuilt->hint_no_need_to_fetch_extra_cols = FALSE;
+			prebuilt->hint_need_to_fetch_extra_cols
+					= ROW_RETRIEVE_ALL_COLS;
+			break;
+	        case HA_EXTRA_RETRIEVE_PRIMARY_KEY:
+			if (prebuilt->hint_need_to_fetch_extra_cols == 0) {
+				prebuilt->hint_need_to_fetch_extra_cols
+					= ROW_RETRIEVE_PRIMARY_KEY;
+			}
 			break;
 	        case HA_EXTRA_KEYREAD:
 	        	prebuilt->read_just_key = 1;
@@ -4575,7 +4587,7 @@ ha_innobase::start_stmt(
 
 	auto_inc_counter_for_this_stat = 0;
 	prebuilt->sql_stat_start = TRUE;
-	prebuilt->hint_no_need_to_fetch_extra_cols = TRUE;
+	prebuilt->hint_need_to_fetch_extra_cols = 0;
 	prebuilt->read_just_key = 0;
 
 	if (!prebuilt->mysql_has_locked) {
@@ -4652,7 +4664,7 @@ ha_innobase::external_lock(
 	trx = prebuilt->trx;
 
 	prebuilt->sql_stat_start = TRUE;
-	prebuilt->hint_no_need_to_fetch_extra_cols = TRUE;
+	prebuilt->hint_need_to_fetch_extra_cols = 0;
 
 	prebuilt->read_just_key = 0;
 
@@ -4996,7 +5008,7 @@ ha_innobase::innobase_read_and_init_auto_inc(
   	/* Play safe and also give in another way the hint to fetch
   	all columns in the key: */
   	
-	prebuilt->hint_no_need_to_fetch_extra_cols = FALSE;
+	prebuilt->hint_need_to_fetch_extra_cols = ROW_RETRIEVE_ALL_COLS;
 
 	prebuilt->trx->mysql_n_tables_locked += 1;
   

sql/sql_select.cc

@@ -845,7 +845,7 @@ JOIN::optimize()
     for (uint i_h = const_tables; i_h < tables; i_h++)
     {
       TABLE* table_h = join_tab[i_h].table;
-      table_h->file->extra(HA_EXTRA_RETRIEVE_ALL_COLS);
+      table_h->file->extra(HA_EXTRA_RETRIEVE_PRIMARY_KEY);
     }
   }
 #endif