diff options
Diffstat (limited to 'sql/handler.h')
| -rw-r--r-- | sql/handler.h | 37 |
1 files changed, 29 insertions, 8 deletions
diff --git a/sql/handler.h b/sql/handler.h index 9d159771097..e1a3409f1c9 100644 --- a/sql/handler.h +++ b/sql/handler.h @@ -4029,6 +4029,7 @@ public: virtual void set_part_info(partition_info *part_info) {return;} virtual void return_record_by_parent() { return; } + /* Information about index. Both index and part starts from 0 */ virtual ulong index_flags(uint idx, uint part, bool all_parts) const =0; uint max_record_length() const @@ -4168,30 +4169,52 @@ public: } /* - Check if the primary key (if there is one) is a clustered and a - reference key. This means: + Check if the key is a clustering key - Data is stored together with the primary key (no secondary lookup needed to find the row data). The optimizer uses this to find out the cost of fetching data. - - The primary key is part of each secondary key and is used + + Note that in many cases a clustered key is also a reference key. + This means that: + + - The key is part of each secondary key and is used to find the row data in the primary index when reading trough secondary indexes. - When doing a HA_KEYREAD_ONLY we get also all the primary key parts into the row. This is critical property used by index_merge. All the above is usually true for engines that store the row - data in the primary key index (e.g. in a b-tree), and use the primary + data in the primary key index (e.g. in a b-tree), and use the key key value as a position(). InnoDB is an example of such an engine. - For such a clustered primary key, the following should also hold: + For a clustered (primary) key, the following should also hold: index_flags() should contain HA_CLUSTERED_INDEX table_flags() should contain HA_TABLE_SCAN_ON_INDEX + For a reference key the following should also hold: + table_flags() should contain HA_PRIMARY_KEY_IS_READ_INDEX. + @retval TRUE yes @retval FALSE No. */ - virtual bool primary_key_is_clustered() { return FALSE; } + + /* The following code is for primary keys */ + bool pk_is_clustering_key(uint index) const + { + /* + We have to check for MAX_INDEX as table->s->primary_key can be + MAX_KEY in the case where there is no primary key. + */ + return index != MAX_KEY && is_clustering_key(index); + } + /* Same as before but for other keys, in which case we can skip the check */ + bool is_clustering_key(uint index) const + { + DBUG_ASSERT(index != MAX_KEY); + return (index_flags(index, 0, 1) & HA_CLUSTERED_INDEX); + } + virtual int cmp_ref(const uchar *ref1, const uchar *ref2) { return memcmp(ref1, ref2, ref_length); @@ -4921,8 +4944,6 @@ public: virtual void update_partition(uint part_id) {} - virtual bool is_clustering_key(uint index) { return false; } - /** Some engines can perform column type conversion with ALGORITHM=INPLACE. These functions check for such possibility. |