?? fastdb.htm
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<HTML>
<HEAD>
<TITLE>FastDB Main Memory Database Management System</TITLE>
<UL>
<LI> <A HREF = "#introduction">Introduction</A>
<LI> <A HREF = "#sql">Query language</A>
<UL>
<LI> <A HREF = "#structure">Structures</A>
<LI> <A HREF = "#array">Arrays</A>
<LI> <A HREF = "#string">Strings</A>
<LI> <A HREF = "#reference">References</A>
<LI> <A HREF = "#rectangle">Rectangle</A>
<LI> <A HREF = "#function">Functions</A>
</UL>
<LI> <A HREF = "#cpp">C++ interface</A>
<UL>
<LI> <A HREF = "#table">Table</A>
<LI> <A HREF = "#query">Query</A>
<LI> <A HREF = "#cursor">Cursor</A>
<LI> <A HREF = "#database">Database</A>
</UL>
<LI> <A HREF = "#cli">CLI - call level interface</A>
<UL>
<LI> <A HREF = "#cli_errors">CLI error codes</A>
<LI> <A HREF = "#cli_types">CLI supported types</A>
<LI> <A HREF = "#cli_open">cli_open</A>
<LI> <A HREF = "#cli_close">cli_close</A>
<LI> <A HREF = "#cli_statement">cli_statement</A>
<LI> <A HREF = "#cli_parameter">cli_parameter</A>
<LI> <A HREF = "#cli_column">cli_colunm</A>
<LI> <A HREF = "#cli_array_column">cli_array_column</A>
<LI> <A HREF = "#cli_fetch">cli_fetch</A>
<LI> <A HREF = "#cli_insert">cli_insert</A>
<LI> <A HREF = "#cli_get_first">cli_get_first</A>
<LI> <A HREF = "#cli_get_last">cli_get_last</A>
<LI> <A HREF = "#cli_get_next">cli_get_next</A>
<LI> <A HREF = "#cli_get_prev">cli_get_prev</A>
<LI> <A HREF = "#cli_get_oid">cli_get_oid</A>
<LI> <A HREF = "#cli_update">cli_update</A>
<LI> <A HREF = "#cli_remove">cli_remove</A>
<LI> <A HREF = "#cli_close_cursor">cli_close_cursor</A>
<LI> <A HREF = "#cli_free">cli_free</A>
<LI> <A HREF = "#cli_commit">cli_commit</A>
<LI> <A HREF = "#cli_abort">cli_abort</A>
<LI> <A HREF = "#cli_show_tables">cli_show_tables</A>
<LI> <A HREF = "#cli_describe">cli_describe</A>
<LI> <A HREF = "#cli_describe_layout">cli_describe_layout</A>
<LI> <A HREF = "#cli_create_table">cli_create_table</A>
<LI> <A HREF = "#cli_alter_table">cli_alter_table</A>
<LI> <A HREF = "#cli_drop_table">cli_drop_table</A>
<LI> <A HREF = "#cli_alter_index">cli_alter_index</A>
<LI> <A HREF = "#cli_freeze">cli_freeze</A>
<LI> <A HREF = "#cli_unfreeze">cli_unfreeze</A>
<LI> <A HREF = "#cli_seek">cli_seek</A>
<LI> <A HREF = "#cli_skip">cli_skip</A>
</UL>
<LI> <A HREF = "#localcli">Local implementation of CLI</A>
<UL>
<LI> <A HREF = "#cli_create">cli_create</A>
<LI> <A HREF = "#cli_create_replication_node">cli_create_replication_node</A>
<LI> <A HREF = "#cli_attach">cli_attach</A>
<LI> <A HREF = "#cli_detach">cli_detach</A>
<LI> <A HREF = "#cli_create_transaction_context">cli_create_transaction_context</A>
<LI> <A HREF = "#cli_join_transaction">cli_join_transaction</A>
<LI> <A HREF = "#cli_remove_transaction_context">cli_remove_transaction_context</A>
<LI> <A HREF = "#cli_get_database_state">cli_get_database_state</A>
<LI> <A HREF = "#cli_prepare_query">cli_prepare_query</A>
<LI> <A HREF = "#cli_execute_query">cli_execute_query</A>
<LI> <A HREF = "#cli_execute_query_ex">cli_execute_query_ex</A>
<LI> <A HREF = "#cli_insert_struct">cli_insert_struct</A>
</UL>
<LI> <A HREF = "jnicli/docs/index.html">Native interface to Java language</A>
<LI> <A HREF = "#advanced">Delayed transactions and online backup scheduler</A>
<LI> <A HREF = "#replication">Fault tolerant support</A>
<LI> <A HREF = "#optimization">Query optimization</A>
<UL>
<LI> <A HREF = "#indices">Using indices in queries</A>
<LI> <A HREF = "#inverse">Inverse references</A>
<LI> <A HREF = "#realtime">Realtime issues</A>
<LI> <A HREF = "#par">Parallel query execution</A>
</UL>
<LI> <A HREF = "#gist">Generalized search tree</A>
<LI> <A HREF = "#implementation">FastDB implementation issues</A>
<UL>
<LI> <A HREF = "#memory">Memory allocation</A>
<LI> <A HREF = "#transaction">Transactions</A>
<LI> <A HREF = "#recovery">Recovery</A>
<LI> <A HREF = "#hashtable">Hash table</A>
<LI> <A HREF = "#ttree">T-tree</A>
</UL>
<LI> <A HREF = "#subsql">Interactive SQL</A>
<LI> <A HREF = "#www">API for development Web applications</A>
<LI> <A HREF = "#examples">Examples of FastDB applications</A>
<UL>
<LI> <A HREF = "#guess">Example: game "Guess an animal"</A>
<LI> <A HREF = "#testdb">Example: various types of queries</A>
<LI> <A HREF = "#testperf">Performance test</A>
<LI> <A HREF = "#bugdb">Bug tracking database</A>
<LI> <A HREF = "#clidb">Clients-Managers database</A>
</UL>
<LI> <A HREF = "#quick">Quick start</A>
<LI> <A HREF = "#dbsize">Reducing initial size of the database file</A>
<LI> <A HREF = "#diskless">Diskless configuration</A>
<LI> <A HREF = "#sharing">Sharing of classes between different databases</A>
<LI> <A HREF = "docs/html/index.html">Documentation generated by Doxygen</A>
<LI> <A HREF = "#distribution">Distribution terms</A>
</UL>
<BODY>
<HR>
<H2><A NAME = "introduction">Introduction</A></H2>
FastDB is a highly efficient main memory database system
with realtime capabilities and convenient C++ interface.
FastDB doesn't support a client-server architecture and all applications
using a FastDB database should run at the same host. FastDB is optimized
for applications with dominated read access pattern. High speed of query
execution is provided by the elimination of data transfer overhead and
a very effective locking implementation. The Database file is mapped to the virtual
memory space of each application working with the database. So the query is executed in
the context of the application, requiring no context switching and data transfer.
Synchronization of concurrent database access is implemented in FastDB
by means of atomic instructions, adding almost
no overhead to query processing. FastDB assumes that the whole database is
present in RAM and optimizes the search algorithms and structures according to this
assumption. Moreover, FastDB has no overhead caused by database buffer management
and needs no data transfer between a database file and buffer pool.
That is why FastDB
will work significantly faster than a traditional database with all data cached
in buffers pool.<P>
FastDB supports transactions, online backup and automatic recovery
after system crash. The transaction commit protocol is based on
a shadow root pages algorithm, performing atomic update of the database.
Recovery can be done very fast, providing
high availability for critical applications. Moreover, the elimination
of transaction logs improves the total system performance and leads to a more
effective usage of system resources.<P>
FastDB is an application-oriented database. Database tables are constructed using
information about application classes. FastDB supports automatic scheme
evaluation, allowing you to do changes only in one place - in your
application classes. FastDB provides a flexible and convenient interface
for retrieving data from the database. A SQL-like query language is used
to specify queries. Such post-relational capabilities as non-atomic
fields, nested arrays, user-defined types and methods, direct interobject
references simplifies the design of database applications and makes them more
efficient.<P>
Although FastDB is optimized in the assumption that database as a whole fits
into the physical memory of the computer, it is also possible to use it with databases,
the size of which exceeds the size of the physical memory in the system. In the last
case, standard operating system swapping mechanisms will work. But
all FastDB search algorithms and structures are optimized under the assumption of
residence of all data in memory, so the efficiency for swapped
out data will not be very high.<P>
<H2><A NAME = "sql">Query language</A></H2>
FastDB supports a query language with SQL-like syntax. FastDB uses a notation more
popular for object-oriented programming then for a relational database.
Table rows are considered as object instances, the table is the class of these
objects. Unlike SQL, FastDB is oriented on work with objects instead of SQL
tuples. So the result of each query execution is a set of objects of one
class. The main differences of the FastDB query language from standard SQL are:<P>
<OL>
<LI> There are no joins of several tables and nested subqueries. The query always
returns a set of objects from one table.
<LI> Standard C types are used for atomic table columns.
<LI> There are no NULL values, except null references.
I completely agree with C.J. Date's criticism of three-value logic and his
proposal to use default values instead.
<LI> Structures and arrays can be used as record components. A special
<B>exists</B> quantor is provided for locating elements in arrays.
<LI> Parameterless user methods can be defined for table records (objects) as well as
for record components.
<LI> User functions with (only) one single string or numeric argument can be defined by
the application.
<LI> References between objects are supported including automatic support
for inverse references.
<LI>Construction of <code>start from follow by</code> performs a recursive records
traversal using references.
<LI> Because the query language is deeply integrated into C++ classes, a case
sensitive mode is used for language identifiers as well as for keywords.
<LI> No implicit conversion of integer and floating types to string
representation is done. If such conversion is needed, it must be done explicitly.
</OL><P>
The following rules in BNF-like notation specify the grammar of the
FastDB query language search predicates:<P>
<TABLE BORDER ALIGN="center">
<CAPTION>Grammar conventions</CAPTION>
<TR><TH>Example</TH><TH>Meaning</TH></TR>
<TR><TD><I>expression</I></TD><TD>non-terminals</TD></TR>
<TR><TD><B>not</B></TD><TD>terminals</TD></TR>
<TR><TD ALIGN="center">|</TD><TD>disjoint alternatives</TD></TR>
<TR><TD>(<B>not</B>)</TD><TD>optional part</TD></TR>
<TR><TD>{<B>1</B>..<B>9</B>}</TD><TD>repeat zero or more times</TD></TR>
</TABLE><P>
<PRE>
<I>select-condition</I> ::= ( <I>expression</I> ) ( <I>traverse</I> ) ( <I>order</I> )
<I>expression</I> ::= <I>disjunction</I>
<I>disjunction</I> ::= <I>conjunction</I>
| <I>conjunction</I> <B>or</B> <I>disjunction</I>
<I>conjunction</I> ::= <I>comparison</I>
| <I>comparison</I> <B>and</B> <I>conjunction</I>
<I>comparison</I> ::= <I>operand</I> <B>=</B> <I>operand</I>
| <I>operand</I> <B>!=</B> <I>operand</I>
| <I>operand</I> <B><></B> <I>operand</I>
| <I>operand</I> <B><</B> <I>operand</I>
| <I>operand</I> <B><=</B> <I>operand</I>
| <I>operand</I> <B>></B> <I>operand</I>
| <I>operand</I> <B>>=</B> <I>operand</I>
| <I>operand</I> (<B>not</B>) <B>like</B> <I>operand</I>
| <I>operand</I> (<B>not</B>) <B>like</B> <I>operand</I> <B>escape</B> <I>string</I>
| <I>operand</I> (<B>not</B>) <B>match</B> <I>operand</I>
| <I>operand</I> (<B>not</B>) <B>in</B> <I>operand</I>
| <I>operand</I> (<B>not</B>) <B>in</B> <I>expressions-list</I>
| <I>operand</I> (<B>not</B>) <B>between</B> <I>operand</I> <B>and</B> <I>operand</I>
| <I>operand</I> <B>is</B> (<B>not</B>) <B>null</B>
<I>operand</I> ::= <I>addition</I>
<I>additions</I> ::= <I>multiplication</I>
| <I>addition</I> <B>+</B> <I>multiplication</I>
| <I>addition</I> <B>||</B> <I>multiplication</I>
| <I>addition</I> <B>-</B> <I>multiplication</I>
<I>multiplication</I> ::= <I>power</I>
| <I>multiplication</I> <B>*</B> <I>power</I>
| <I>multiplication</I> <B>/</B> <I>power</I>
<I>power</I> ::= <I>term</I>
| <I>term</I> <B>^</B> <I>power</I>
<I>term</I> ::= <I>identifier</I> | <I>number</I> | <I>string</I>
| <B>true</B> | <B>false</B> | <B>null</B>
| <B>current</B> | <B>first</B> | <B>last</B>
| <B>(</B> expression <B>)</B>
| <B>not</B> <I>comparison</I>
| <B>-</B> term
| <I>term</I> <B>[</B> expression <B>]</B>
| <I>identifier</I> <B>.</B> <I>term</I>
| <I>function</I> <I>term</I>
| <B>exists</B> <I>identifier</I> <B>:</B> <I>term</I>
<I>function</I> ::= <B>abs</B> | <B>length</B> | <B>lower</B> | <B>upper</B>
| <B>integer</B> | <B>real</B> | <B>string</B> | <I>user-function</I>
<I>string</I> ::= <B>'</B> { { <I>any-character-except-quote</I> } (<B>''</B>) } <B>'</B>
<I>expressions-list</I> ::= <B>(</B> <I>expression</I> { <B>,</B> <I>expression</I> } <B>)</B>
<I>order</I> ::= <B>order by</B> <I>sort-list</I>
<I>sort-list</I> ::= <I>field-order</I> { <B>,</B> <I>field-order</I> }
<I>field-order</I> ::= [<B>length</B>] <I>field</I> (<B>asc</B> | <B>desc</B>)
<I>field</I> ::= <I>identifier</I> { <B>.</B> <I>identifier</I> }
<I>traverse</I> ::= <B>start from</B> <I>field</I> ( <B>follow by</B> <I>fields-list</I> )
<I>fields-list</I> ::= <I>field</I> { <B>,</B> <I>field</I> }
<I>user-function</I> ::= <I>identifier</I>
</PRE><P>
Identifiers are case sensitive, begin with a a-z, A-Z, '_' or '$'
character, contain only a-z, A-Z, 0-9, '_' or '$' characters, and
do not duplicate a SQL reserved word.<P>
<TABLE WIDTH=100%>
<CAPTION>List of reserved words</CAPTION>
<TR><TD>abs</TD><TD>and</TD><TD>asc</TD><TD>between</TD><TD>by</TD></TR>
<TR><TD>current</TD><TD>desc</TD><TD>escape</TD><TD>exists</TD><TD>false</TD></TR>
<TR><TD>first</TD><TD>follow</TD><TD>from</TD><TD>in</TD><TD>integer</TD></TR>
<TR><TD>is</TD><TD>length</TD><TD>like</TD><TD>last</TD><TD>lower</TD></TR>
<TR><TD>match</TD><TD>not</TD><TD>null</TD><TD>or</TD><TD>real</TD></TR>
<TR><TD>rectangle</TD><TD>start</TD><TD>string</TD><TD>true</TD><TD>upper</TD></TR>
</TABLE><P>
ANSI-standard comments may also be used. All characters after a double-hyphen up to
the end of the line are ignored.<P>
FastDB extends ANSI standard SQL operations by supporting bit manipulation
operations. Operators <code>and</code>/<code>or</code> can be applied not only
to boolean operands but also to operands of integer type. The result of applying the
<code>and</code>/<code>or</code> operator to integer operands is an integer
value with bits set by the bit-AND/bit-OR operation. Bit operations can be used
for efficient implementation of small sets. Also the rasing to a power
operation (x<B>^</B>y) is supported by FastDB for integer and floating point
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