8.4.7 The DBLQH Block

This is the local, low-level query handler block, which manages data and transactions local to the cluster's data nodes, and acts as a coordinator of 2-phase commits. It is responsible (when called on by the transaction coordinator) for performing operations on tuples, accomplishing this task with help of DBACC block (which manages the index structures) and DBTUP (which manages the tuples). It is made up of the following files, found in storage/ndb/src/kernel/blocks/dblqh:

This block also handles redo logging, and helps oversee the DBACC, DBTUP, LGMAN, TSMAN, PGMAN, and BACKUP blocks. It is implemented as the class Dblqh, defined in the file storage/ndb/src/kernel/blocks/dblqh/Dblqh.hpp.