handle cardinality with alter add drop

storage/tokudb/ha_tokudb_alter_56.cc

@@ -22,6 +22,7 @@ public:
         alter_txn(NULL),
         add_index_changed(false),
         drop_index_changed(false),
+        reset_card(false),
         compression_changed(false),
         expand_varchar_update_needed(false),
         expand_fixed_update_needed(false),
@@ -38,6 +39,7 @@ public:
     bool add_index_changed;
     bool incremented_num_DBs, modified_DBs;
     bool drop_index_changed;
+    bool reset_card;
     bool compression_changed;
     enum toku_compression_method orig_compression_method;
     bool expand_varchar_update_needed;
@@ -366,7 +368,6 @@ bool ha_tokudb::inplace_alter_table(TABLE *altered_table, Alter_inplace_info *ha
     }
     if (error == 0 && (ctx->handler_flags & Alter_inplace_info::CHANGE_CREATE_OPTION) && (create_info->used_fields & HA_CREATE_USED_ROW_FORMAT)) {
         // Get the current compression
-        tokudb_alter_ctx *ctx = static_cast<tokudb_alter_ctx *>(ha_alter_info->handler_ctx);
         DB *db = share->key_file[0];
         error = db->get_compression_method(db, &ctx->orig_compression_method);
         assert(error == 0);
@@ -388,6 +389,9 @@ bool ha_tokudb::inplace_alter_table(TABLE *altered_table, Alter_inplace_info *ha
     if (error == 0 && ctx->expand_fixed_update_needed)
         error = alter_table_expand_columns(altered_table, ha_alter_info);
 
+    if (error == 0 && ctx->reset_card)
+        tokudb::set_card_from_status(share->status_block, ctx->alter_txn, table->s, altered_table->s);
+
     bool result = false; // success
     if (error) {
         print_error(error, MYF(0));
@@ -422,7 +426,7 @@ int ha_tokudb::alter_table_add_index(TABLE *altered_table, Alter_inplace_info *h
     my_free(key_info);
     
     if (error == 0)
-        tokudb::set_card_from_status(share->status_block, ctx->alter_txn, table->s, altered_table->s);
+        ctx->reset_card = true;
 
     return error;
 }
@@ -469,7 +473,7 @@ int ha_tokudb::alter_table_drop_index(TABLE *altered_table, Alter_inplace_info *
     int error = drop_indexes(table, index_drop_offsets, ha_alter_info->index_drop_count, key_info, ctx->alter_txn);
 
     if (error == 0)
-        tokudb::set_card_from_status(share->status_block, ctx->alter_txn, table->s, altered_table->s);
+        ctx->reset_card = true;
 
     return error;
 }

storage/tokudb/tokudb_card.h

@@ -76,25 +76,24 @@ namespace tokudb {
         return false;
     }
 
+    // Altered table cardinality = select cardinality data from current table cardinality for keys that exist 
+    // in the altered table and the current table.
     void set_card_from_status(DB *status_db, DB_TXN *txn, TABLE_SHARE *table_share, TABLE_SHARE *altered_table_share) {
         int error;
-
         // read existing cardinality data from status
         uint64_t rec_per_key[table_share->key_parts];
         error = get_card_from_status(status_db, txn, table_share->key_parts, rec_per_key);
-
+        // set altered records per key to unknown
         uint64_t altered_rec_per_key[altered_table_share->key_parts];
         for (uint i = 0; i < altered_table_share->key_parts; i++)
             altered_rec_per_key[i] = 0;
-
-        // compute the beginning of the key offsets
+        // compute the beginning of the key offsets in the original table
         uint orig_key_offset[table_share->keys];
         uint orig_key_parts = 0;
         for (uint i = 0; i < table_share->keys; i++) {
             orig_key_offset[i] = orig_key_parts;
             orig_key_parts += table_share->key_info[i].key_parts;
         }
-
         // if orig card data exists, then use it to compute new card data
         if (error == 0) {
             uint key_parts = 0;
@@ -123,6 +122,7 @@ namespace tokudb {
         uint64_t rows = 0;
         uint64_t unique_rows[num_key_parts];
         if (is_unique && num_key_parts == 1) {
+            // dont compute for unique keys with a single part.  we already know the answer.
             rows = unique_rows[0] = 1;
         } else {
             DBC *cursor = NULL;