4.10 The DBTUP Block

This is the tuple manager, which manages the physical storage of cluster data. It consists of the following files found in the directory storage/ndb/src/kernel/blocks/dbtup:

• AttributeOffset.hpp: Defines the AttributeOffset class, which models the structure of an attribute, permitting up to 4096 attributes, all of which are nullable.

• DbtupDiskAlloc.cpp: Handles allocation and deallocation of extents for disk space.

• DbtupIndex.cpp: Implements methods for reading and writing tuples using ordered indexes.

• DbtupScan.cpp: Implements methods for tuple scans.

• tuppage.cpp: Handles allocating pages for writing tuples.

• tuppage.hpp: Defines structures for fixed and variable size data pages for tuples.

• DbtupAbort.cpp: Contains routines for terminating failed tuple operations.

• DbtupExecQuery.cpp: Handles execution of queries for tuples and reading from them.

• DbtupMeta.cpp: Handle table operations for the Dbtup class.

• DbtupStoredProcDef.cpp: Module for adding and dropping procedures.

• DbtupBuffer.cpp: Handles read/write buffers for tuple operations.

• DbtupFixAlloc.cpp: Allocates and frees fixed-size tuples from the set of pages attatched to a fragment. The fixed size is set per fragment; there can be only one such value per fragment.

• DbtupPageMap.cpp: Routines used by Dbtup to map logical page IDs to physical page IDs. The mapping needs the fragment ID and the logical page ID to provide the physical ID. This part of Dbtup is the exclusive user of a certain set of variables on the fragment record; it is also the exclusive user of the struct for page ranges (the PageRange struct defined in Dbtup.hpp).

• DbtupTabDesMan.cpp: This file contains the routines making up the table descriptor memory manager. Each table has a descriptor, which is a contiguous array of data words, and which is allocated from a global array using a “buddy” algorithm, with free lists existing for each 2^N words.

• Notes.txt: Contains some developers' implementation notes on tuples, tuple operations, and tuple versioning.

• Undo_buffer.hpp: Defines the Undo_buffer class, used for storage of operations that may need to be rolled back.

• Undo_buffer.cpp: Implements some necessary Undo_buffer methods.

• DbtupCommit.cpp: Contains routines used to commit operations on tuples to disk.

• DbtupGen.cpp: This file contains Dbtup initialization routines.

• DbtupPagMan.cpp: This file implements the page memory manager's “buddy” algorithm. PagMan is invoked when fragments lack sufficient internal page space to accommodate all the data they are requested to store. It is also invoked when fragments deallocate page space back to the free area.

• DbtupTrigger.cpp: The routines contained in this file perform handling of NDB internal triggers.

• DbtupDebug.cpp: Used for debugging purposes only.

• Dbtup.hpp: Contains the Dbtup class definition. Also defines a number of essential structures such as tuple scans, disk allocation units, fragment records, and so on.

• DbtupRoutines.cpp: Implements Dbtup routines for reading attributes.

• DbtupVarAlloc.cpp

• test_varpage.cpp: Simple test program for verifying variable-size page operations.

This block also monitors changes in tuples.

DBQTUP is a subtype of this block, used for query and recovery threads, added in NDB 8.0.23.