Hi,
We are trying to analyse the architecture of mysql with
respect to layering. As Petr suggested we reorganized the mapping of
modules to layers as follows:
Layer 3 (Application/top level) : client, libmysql, libmysqld,
libmysql_r, tests, mysql-test
Layer 2 (QueryProcessing) : sql
Layer 1 (StorageManagement) : heap, innobase, myisam, ndb, isam,
bdatabase, myisammrg, merge
Layer 0 (library/utilities) :
mysys,cmd-line-utils,extra,netware,os2,pstack,regex,zlib,vio,strings,SSL
,support-files,tools,include,dbug
The rationale for this layering is that the layer above would use the
services provided by layers below.
We have a couple of questions:
1. There are 3 versions of sql_string.h : client/sql_string.h,
libmysqld/sql_string.h and sql/sql_string.h. Do we need 3 versions?
2. libmysqld has a copy of many files that exist in other
directories (eg. Sql_cache.cc exists in both libmysqld and sql) So if
one of the files change would you not have to make changes in both the
places?
3. There are function calls from sql (in layer 2) to libmysqld (in
layer 3) . For example function "query_cache_end_of_result" in file
sql/sql_cache.cc calls the function "emb_count_querycache_size" in file
libmysqld/emb_qcache.cc. Is this intended?
Thanks in advance
Girish
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