I was writing this in an email to a co-worker today, could possibly interest people in the outside world as well. It’s a good idea to look at the source at the same time as reading this :)<\/p>\n
In ha_ndbcluster::write_row(byte*),<\/p>\n
We set next_insert_id to 0 so that in handler::update_auto_increment() we end calling the handler and never doing it just inside the server.<\/p>\n The handler function that we end up in is: ha_ndbcluster::get_auto_increment().<\/p>\n From here we end up inside NDB to do the actual work (not in the table handler).<\/p>\n Looking inside storage\/ndb\/src\/ndbapi\/Ndb.cpp at the method:<\/p>\n Ndb::getAutoIncrementValue(NdbDictionary::Table*,Uint32)<\/p>\n which really just calls Ndb::getTupleIdFromNdb(Uint32,Uint32) This increments an entry in the SYSTAB_0 table inside the sys database in NDB. The row with SYSKEY_0 equal to the table id keeps the auto increment value. You can watch this by using a tool such as ndb_select_all on this table (grepping for the table id which you found with ndb_show_tables) while inserting rows into a table with an auto_increment value.<\/p>\n","protected":false},"excerpt":{"rendered":" I was writing this in an email to a co-worker today, could possibly interest people in the outside world as well. It’s a good idea to look at the source at the same time as reading this :) In ha_ndbcluster::write_row(byte*), … Continue reading if (table_share->primary_key != MAX_KEY)
\n{
\n\/*
\n* Increase any auto_incremented primary key
\n*\/
\nif (has_auto_increment)
\n{
\nTHD *thd= table->in_use;<\/code><\/p>\nm_skip_auto_increment= FALSE;
\nupdate_auto_increment();
\n\/* Ensure that handler is always called for auto_increment values *\/
\nthd->next_insert_id= 0;
\nm_skip_auto_increment= !auto_increment_column_changed;
\n}
\n}<\/code><\/p>\n
\nwhich either returns a cached value, or goes off and does a call to NDB to get either 1 auto increment value or the full cacheSize we’ve requested (which is worked out in ha_ndbcluster::get_auto_increment()). This increment is done in the interestingly named Ndb::opTupleIdOnNdb(Uint32 aTableId, Uint64 opValue, Uint32 op) (with op=0).<\/p>\n