MDEV-371 Unique Index for long columns

This patch implements engine independent unique hash index.

Usage:- Unique HASH index can be created automatically for blob/varchar/test column whose key
 length > handler->max_key_length()
or it can be explicitly specified.

  Automatic Creation:-
   Create TABLE t1 (a blob unique);
  Explicit Creation:-
   Create TABLE t1 (a int , unique(a) using HASH);

Internal KEY_PART Representations:-
 Long unique key_info will have 2 representations.
 (lets understand this with an example create table t1(a blob, b blob , unique(a, b)); )

 1. User Given Representation:- key_info->key_part array will be similar to what user has defined.
 So in case of example it will have 2 key_parts (a, b)

 2. Storage Engine Representation:- In this case there will be only one key_part and it will point to
 HASH_FIELD. This key_part will be always after user defined key_parts.

 So:- User Given Representation          [a] [b] [hash_key_part]
                  key_info->key_part ----^
  Storage Engine Representation          [a] [b] [hash_key_part]
                  key_info->key_part ------------^

 Table->s->key_info will have User Given Representation, While table->key_info will have Storage Engine
 Representation.Representation can be changed into each other by calling re/setup_keyinfo_hash function.

Working:-

1. So when user specifies HASH_INDEX or key_length is > handler->max_key_length(), In mysql_prepare_create_table
One extra vfield is added (for each long unique key). And key_info->algorithm is set to HA_KEY_ALG_LONG_HASH.

2. In init_from_binary_frm_image values for hash_keypart is set (like fieldnr , field and flags)

3. In parse_vcol_defs, HASH_FIELD->vcol_info is created. Item_func_hash is used with list of Item_fields,
   When Explicit length is given by user then Item_left is used to concatenate Item_field values.

4. In ha_write_row/ha_update_row check_duplicate_long_entry_key is called which will create the hash key from
table->record[0] and then call ha_index_read_map , if we found duplicated hash , we will compare the result
field by field.

1 files changed, 6 insertions, 6 deletions

diff --git a/storage/oqgraph/oqgraph_thunk.cc b/storage/oqgraph/oqgraph_thunk.cc
index 5e254450a2b..09cc9c1798b 100644
--- a/storage/oqgraph/oqgraph_thunk.cc
+++ b/storage/oqgraph/oqgraph_thunk.cc
@@ -109,7 +109,7 @@ const std::string& oqgraph3::cursor::record_position() const
     if (_graph->_cursor->_index >= 0)
     {
       key_copy((uchar*) _graph->_cursor->_key.data(), table.record[0],
-          table.s->key_info + _index, table.s->key_info[_index].key_length, true);
+          table.key_info + _index, table.key_info[_index].key_length, true);
     }
 
     _graph->_stale= false;
@@ -184,7 +184,7 @@ int oqgraph3::cursor::restore_position()
     if (int rc= table.file->ha_index_read_map(
                     table.record[0], (const uchar*) _key.data(),
                     (key_part_map)(1 << _parts) - 1,
-                    table.s->key_info[_index].user_defined_key_parts == _parts ?
+                    table.key_info[_index].user_defined_key_parts == _parts ?
                         HA_READ_KEY_EXACT : HA_READ_KEY_OR_NEXT))
     {
       table.file->ha_index_end();
@@ -368,7 +368,7 @@ int oqgraph3::cursor::seek_to(
     if (!destid)
     {
       int i= 0;
-      for( ::KEY *key_info= table.s->key_info,
+      for( ::KEY *key_info= table.key_info,
                  *key_end= key_info + table.s->keys;
           key_info < key_end; ++key_info, ++i)
       {
@@ -399,7 +399,7 @@ int oqgraph3::cursor::seek_to(
     else if (!origid)
     {
       int i= 0;
-      for( ::KEY *key_info= table.s->key_info,
+      for( ::KEY *key_info= table.key_info,
                  *key_end= key_info + table.s->keys;
           key_info < key_end; ++key_info, ++i)
       {
@@ -430,7 +430,7 @@ int oqgraph3::cursor::seek_to(
     else
     {
       int i= 0;
-      for( ::KEY *key_info= table.s->key_info,
+      for( ::KEY *key_info= table.key_info,
                  *key_end= key_info + table.s->keys;
           key_info < key_end; ++key_info, ++i)
       {
@@ -485,7 +485,7 @@ int oqgraph3::cursor::seek_to(
     if (int rc= table.file->ha_index_read_map(
             table.record[0], (uchar*) _key.data(),
             (key_part_map) ((1U << _parts) - 1),
-            table.s->key_info[_index].user_defined_key_parts == _parts ?
+            table.key_info[_index].user_defined_key_parts == _parts ?
                 HA_READ_KEY_EXACT : HA_READ_KEY_OR_NEXT))
     {
       table.file->ha_index_end();