The HEAP (MEMORY) table handler.
All the MySQL table handlers (that is, the handlers that MySQL
itself produces) have files with similar names and functions.
Thus, this (heap) directory contains a lot of duplication of the
myisam directory (for the MyISAM table
handler). Such duplicates have been marked with an "*" in the
following list. For example, you will find that
\heap\hp_extra.c has a close equivalent in
the myisam directory (\myisam\mi_extra.c)
with the same descriptive comment. (Some of the differences
arise because HEAP has different structures.
HEAP does not need to use the sort of B-tree
indexing that ISAM and
MyISAM use; instead there is a hash index.
Most importantly, HEAP is entirely in memory.
File-I/O routines lose some of their vitality in such a
context.)
hp_block.c --- Read/write a block (that is, a page)
hp_clear.c --- Remove all records in the table
hp_close.c --- * close database
hp_create.c --- * create a table
hp_delete.c --- * delete a row
hp_extra.c --- * for setting options and buffer sizes when optimizing
hp_hash.c --- Hash functions used for saving keys
hp_info.c --- * Information about database status
hp_open.c --- * open database
hp_panic.c --- * the hp_panic routine, for shutdowns and flushes
hp_rename.c --- * rename a table
hp_rfirst.c --- * read first row through a specific key (very short)
hp_rkey.c --- * read record using a key
hp_rlast.c --- * read last row with same key as previously-read row
hp_rnext.c --- * read next row with same key as previously-read row
hp_rprev.c --- * read previous row with same key as previously-read row
hp_rrnd.c --- * read a row based on position
hp_rsame.c --- * find current row using positional read or key-based read
hp_scan.c --- * read all rows sequentially
hp_static.c --- * static variables (very short)
hp_test1.c --- * testing basic functions
hp_test2.c --- * testing database and storing results
hp_update.c --- * update an existing row
hp_write.c --- * insert a new row
There are fewer files in the heap directory than in the myisam directory, because fewer are necessary. For example, there is no need for a \myisam\mi_cache.c equivalent (to cache reads) or a \myisam\mi_log.c equivalent (to log statements).