Copyright (C) 2003, 2004 Jeffrey I Cohen. All rights reserved, worldwide. NAME Genezzo::GenDBI - Genezzo engine DESCRIPTION The Genezzo modules implement a hierarchy of persistent hashes using a fixed amount of memory and disk. This system is designed to be easily configured and extended with custom functions, persistent storage representations, and novel data access methods. In its current incarnation it supports a limited SQL-like language with DBI-style interfaces. REQUIREMENTS Perl 5.6 INSTALLATION If you can read this, then you figured out how to uncompress and untar the archive. perl Makefile.PL # constructs the makefile make make test make install # (as superuser) You should be able to run scripts from the directory containing this file, something like: perl -Iblib/lib lib/Genezzo/gendba.pl USAGE line mode available via (/usr/bin) gendba.pl. Try: gendba.pl -help gendba.pl -man for more information. The GenDBI module supports a subset of DBI-style calls. See dbi_example.pl for some sample usage. Try: perl -Iblib/lib lib/Genezzo/dbi_example.pl # runs an example perldoc Genezzo::GenDBI for more information. EXAMPLES The simplest way to create an instance of a Genezzo database is to use: gendba.pl -init This command will create a new database and login to the command-line. Some very basic SQL create/drop/describe table, select, insert, update and delete syntax is supported, but unlike standard SQL, table and column names are case-sensitive. More complex SQL, such as joins, parses, but is ignored. The only supported functions are count(*) and ecount, a non-blocking count estimation function. The database also supports commit to force changes to disk, but no rollback. NOTE: Data definition (such as create table or ct) must be manually committed to keep the database in a consistent state. Uncommitted inserts and updates will only be block-consistent -- there is no guarantee that the data will get flushed to disk, and no guarantee whether the changes will or will not take effect. rem Some simple SELECTs select * from _col1; select rid, rownum, tname, colname from _col1; select count(*) from _col1; select ecount from _col1; rem SELECTs with WHERE, perl and SQL style. rem This functionality is somewhat fragile rem rem note use of /x in regexp - fix problem when parser adds extra space select * from _tab1 where tname =~ m/col/x; select * from _tab1 where tid < 5; select * from _tab1 where (numcols > 3) && (numcols < 6); select tid as Table_ID, tname Name from _tab1; rem Basic INSERT insert into test1 values (a,b,c,d); insert into test1(col2, col1) values (a,b,c,d); rem CREATE TABLE and INSERT...SELECT create table test2(col1 char, col2 char); insert into test2 (col1) select col1 from test1; rem DELETE with WHERE delete from test1 where (col1 < "bravo") && (col2 > 5); rem UPDATE with WHERE (no subqueries supported) update test2 set col2 = "foo" where col2 is null; commit By default, the database will autostart -- the gendba.pl command will connect to an active, updateable instance. The shutdown command will reset the database to a read-only mode that only provides read access to certain dictionary tables. The startup command will restart the database. The Genezzo parser also supports the Feeble query language, as described by gendba.pl -man. Briefly, the commands are ct (create table), dt (drop table), i (insert), u (update), d (delete), s (select). The following example creates a table EMP with two columns, NAME (as character) and ID (as number), inserts five rows, and counts them. ct EMP NAME=c ID=n i EMP bob 1 orville 2 wilbur 3 harry 4 luke 5 s EMP count s EMP ecount commit Update and delete only work via rowid. For example: gendba 10> s EMP rid rownum * rid rownum NAME ID ___ ______ ____ __ 1/33/1 1 bob 1 1/33/2 2 orville 2 1/33/3 3 wilbur 3 1/33/4 4 harry 4 1/33/5 5 luke 5 5 rows selected. gendba 11> d EMP 1/33/1 deleted 1 rows from table EMP. gendba 12> u EMP 1/33/5 margo 66 updated 1 rows in table EMP. gendba 13> !10 s EMP rid rownum * rid rownum NAME ID ___ ______ ____ __ 1/33/2 1 orville 2 1/33/3 2 wilbur 3 1/33/4 3 harry 4 1/33/5 4 margo 66 4 rows selected. The default database is stored in a fixed-size 160K file. You can change the default filesize and the blocksize at database initialization time. For example: gendba.pl -init -define blocksize=8k -define dbsize=10M to create a database with a 10 megabyte datafile using 8K blocks. By default, this file is a fixed size, but it can be set to grow using the "increase_by" settings added in version 0.18. Also, you can add additional files to your database using the "addfile" command. By default, each file is double the size of the previous. Type "addfile help" for more options. NEW FEATURES - Indexed Tables Version 0.13 introduces an indexed-table type. An indexed table treats the first column in the table definition as a unique, not-null primary key. gendba 9> ct EMP index id=n name=c Create Table : EMP with unique index option tablename : EMP column id : n (primary key) column name : c table EMP created gendba 10> i EMP 1 bob 2 orville 3 wilbur 4 harry 5 luke inserted 5 rows into table EMP. gendba 11> s EMP rid * rid id name ___ __ ____ 1 1 bob 2 2 orville 3 3 wilbur 4 4 harry 5 5 luke 5 rows selected. gendba 12> i EMP 1 bob 2 orville 3 wilbur 4 harry 5 luke whisper: duplicate key 1 Failed to insert row 1 in table EMP at lib/Genezzo/gendba.pl line 230 inserted 0 rows into table EMP. gendba 13> select tid, tname, otype from _tab1 where tname = "EMP" tid tname otype ___ _____ _____ 14 EMP IDXTAB 1 row selected. Notice that the first column is marked as a primary key when the table is created, and the rids for indexed tables are the primary key, not a physical block address. Indexed tables have an object type of IDXTAB in the data dictionary -- conventional tables are marked as TABLE. WHERE clause processing has been enhanced to use equality predicates (e.g. "SELECT * from EMP where id = 2") to drive index scans. Any series of "AND"ed predicates is a candidate for an efficient index search, but the use of an OR currently requires a full table scan. CAVEATS: The index performance is pretty poor, for a couple reasons. It should improve a lot. NEW FEATURES - Primary Key Indexes Version 0.14 introduces "ci" - create index. Users can now define their own primary key (unique and not-null) indexes. The dictionary automatically maintains indexes on its own tables. In order to create an index called EMP_PK on the ID column of table EMP, the command is: ci EMP_PK EMP ID Version 0.15 supports SQL-style Create Index. The alternative method to create the EMP_PK index is: Create Index EMP_PK on EMP (ID) You can have arbitrary combinations of numeric and character keys. RESTRICTIONS: only one index per table currently. Index keys must be less than one-half of the db blocksize. In version 0.15, the query engine will use the index to drive the row fetch for a SELECT if the WHERE clause specifies an equality predicate on the primary key. For example: Select * from EMP where ID = 5 uses an index. In general, additional predicates may accompany the equality expression as long as they are ANDed: Select * from EMP where ID = 5 and NAME =~ m/BOB/x However, the presence of ORs causes the plan to revert to a full table scan: Select * from EMP where ID = 5 or ID = 6 NEW FEATURES - automatic tablespace and file growth In version 0.18, datafiles are no longer a fixed size. The column "increase_by" in table _tsfiles controls the behavior: if this column is blank, null, or zero, the datafile size is fixed. If "increase_by" is a non-zero number, the datafile will attempt to grow by that many bytes if it runs out of free extents. If "increase_by" is a percentage like "50%", the datafile is extended by the current size multiplied by this percentage. The AddFile command now takes "increase_by" as an optional argument. Also in version 0.18, each tablespace can be configured to automatically create new datafiles when the current datafile runs out of free extents. The column "addfile" in table _tspace controls the behavior: if the column is blank or null, then the tablespace must be extended manually. If the "addfile" column contains a valid argument list for the AddFile command, then this command will get invoked when all of the current datafiles are full. Note that the datafiles can be of a fixed size, or use the new "increase_by" parameter to grow to some maximum size (currently 2G). The script "bigdb.sql" can be used to reset your database for automatic growth. It can be invoked as "@bigdb.sql" from the gendba command line. NEW FEATURES - Non-Unique Indexes In version 0.20, all user-defined indexes are non-unique. Unique indexes should be created as unique constraints (but they aren't implemented yet). NEW FEATURES - ALTER TABLE ADD CONSTRAINT Version 0.20 supports ALTER TABLE ADD CONSTRAINT CHECK (). The check-text is any basic where clause predicate. Example: gendba 3> create table testcon (col1 c, col2 n); gendba 4> alter table testcon add constraint cn1 check ((col2 > 5) && col1 =~ m/(a|b|c)/x ) gendba 5> insert into testcon values ("a", 7); inserted 1 row into table testcon. gendba 6> insert into testcon values ("b", 8); inserted 1 row into table testcon. gendba 7> insert into testcon values ("d", 8); violated constraint cn1 whisper: undo insert!! Failed to insert row 1 in table testcon at lib/Genezzo/gendba.pl line 244 inserted 0 rows into table testcon. gendba 8> insert into testcon values ("a", 1); violated constraint cn1 whisper: undo insert!! Failed to insert row 1 in table testcon at lib/Genezzo/gendba.pl line 244 inserted 0 rows into table testcon. Currently, it only supports a single constraint or single index per table. Also, it parses ADD CONSTRAINT UNIQUE (), but does not execute. Sorry. Need to extend to fully support UNIQUE, NOT NULL, PRIMARY, with multiple constraints and indexes per table, plus ENABLE/DISABLE. INCOMPATIBLE CHANGES Version 0.20 dictionary and block format is incompatible with previous release. No upgrade path is supported. SEE ALSO The project homepage at http://genezzo.com AUTHOR Original author: Jeffrey I Cohen Copyright (c) 2003, 2004 Jeffrey I Cohen. All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Address bug reports and comments to: jcohen@genezzo.com