NAME

Genezzo::Dict.pm - The Genezzo data dictionary

SYNOPSIS

 use Genezzo::Dict;
 # create a new dictionary
 my $dictobj = Genezzo::Dict->new(
                  gnz_home => $gnz_home, 
                  init_db => $init);
 
 # see if a table exists
 if ($dictobj->DictTableExists (
                   tname => $tablename,
                   silent_exists => 0,
                   silent_notexists => 1 )))...
 # create a new table
 $dictobj->DictTableCreate (
                   tname => $tablename,
                   tabdef => \%coldatatype,
                   tablespace => "SYSTEM");
 # drop a table
 $dictobj->DictTableDrop (tname => $tablename);
 # save the state of the dictionary to disk
 $dictobj->DictSave();
 my $colhash = 
     $dictobj->DictTableGetCols (tname => $tablename);
 $dictobj->RowInsert (tname => $tablename, 
                      rowval => \@rowarr );
 $dictobj->RowDelete (tname => $tablename, 
                      rid => $rid);
 $dictobj->RowUpdate (tname => $tablename, 
                      rid => $rid,
                      rowval => \@rowarr);
 # return the table as a tied hash
 my $tablehash = 
     $dictobj->DictTableGetTable (tname => $tablename) ;

DESCRIPTION

The dictionary is a complete description of the Genezzo system, recording information on table structure and physical layout. It provides an interface to create, destroy, query, and manipulate tables.

Dictionary concepts

Tablespace -- a physical space to store the contents of tables. A tablespace is a collection of files. The default install of Genezzo creates a single SYSTEM tablespace in a single file.

Core Tables

The dictionary itself is just a set of tables stored in the system tablespace. Genezzo only uses six core tables to describe its basic dictionary. NOTE: Modifying any dictionary tables will framboozle your nimwits. You have been warned.

_pref1 -- a set of key/value pairs that describe the database configuration
_tspace -- the list of tablespaces for this Genezzo instance.
_tsfiles -- the list of files which compose each tablespace
_tab1 -- the list of tables and their associated tablespaces
_col1 -- the list of columns for each table
allfileused -- the list of files actually used by each table

FUNCTIONS

I want to reduce the interface to a simple tied hash, something like:

 my $errormsg;
 %args = (errormsg => \$errormsg );
 my $dicthash = DictGetDictHash(%args);

Checking for the existance of a table would be something like:

 my $tablename = "kitchentable";
 if (exists($dicthash->{tableinfo}->{$tablename}))
 {
    # do stuff...
 }
 else
 {
    # errormsg was reference in tie of dicthash, 
    # contains last error status
    print $errormsg;
 }

EXPORT

TODO

pref1 - distinguish fixed/mutable parameters
cons1 - distinguish user constraint names from system-defined names
IDXTAB indexed tables don't give a constraint error, or primary key error. They don't have constraints because they are themselves indexes. Need to give better error message.
Fix t/Cons1 constraint error
DictTableAllTab: need index on allfileused for delete
DictTableAllTab: update tsfiles for usefile
need some combo _get_table/corecolnum/getcol - create a custom iterator that returns specified cols
non-unique index support using bt2 use_keycount. Need to separate notion of SQL uniqueness from btree concept of unique, since a non-unique SQL index is a unique btree with the rid as least-significant key col (vs rid as value col).
need drop table/drop index linkage, delete constraints for table, etc
constraints: can fix check constraint in update case -- don't need to check insert if check columns aren't modified.
constraints: need not null/foreign key constraints
constraints: need to limit one primary key per table, prevent creation of duplicate indexes on same ordered key columns
expose drop index, drop constraint. tie drop index/drop table?
check usage of HCount for max tid, max fileidx, max consid. This won't work if have deletions
DictTableUseFile: update space management to use this function correctly
DictDefineCoreTabs, tsfiles: need to save file headersize as a tsfile column.
deal with dict->{headersize} attribute in some rational way. Currently set via tablespace->TSAddFile...

AUTHOR

Jeffrey I. Cohen, jcohen@genezzo.com