org.modeshape.sequencer.ddl.package-info Maven / Gradle / Ivy
/*
* ModeShape (http://www.modeshape.org)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* The classes that make up the DDL sequencer, which is capable of parsing the more important DDL statements
* from SQL-92, Oracle, Derby, and PostgreSQL, and constructing a graph structure containing a structured
* representation of these statements.
* The resulting graph structure is largely the same for all dialects, though some dialects have non-standard
* additions to their grammar, and thus require dialect-specific additions to the graph structure.
*
* The sequencer is designed to behave as intelligently as possible with as little configuration.
* Thus, the sequencer automatically determines the dialect used by a given DDL stream. This can be tricky,
* of course, since most dialects are very similar and the distinguishing features of a dialect may only be
* apparent in some of the statements.
*
*
* To get around this, the sequencer uses a "best fit" algorithm: run the DDL stream through the parser for
* each of the dialects, and determine which parser was able to successfully read the greatest number of
* statements and tokens.
*
*
* One very interesting capability of this sequencer is that, although only a subset of the (more common)
* DDL statements are supported, the sequencer is still extremely functional since it does still add all
* statements into the output graph, just without much detail other than just the statement text and the
* position in the DDL file. Thus, if a DDL file contains statements the sequencer understands and statements
* the sequencer does not understand, the graph will still contain all statements, where those statements
* understood by the sequencer will have full detail. Since the underlying parsers are able to operate
* upon a single statement, it is possible to go back later (after the parsers have been enhanced to
* support additional DDL statements) and re-parse only those incomplete statements in the graph.
*
*
* At this time, the sequencer supports SQL-92 standard DDL as well as dialects from Oracle, Derby, and PostgreSQL.
* It supports:
*
* - Detailed parsing of CREATE SCHEMA, CREATE TABLE and ALTER TABLE.
* - Partial parsing of DROP statements
* - General parsing of remaining schema definition statements (i.e. CREATE VIEW, CREATE DOMAIN, etc.
*
* Note that the sequencer does not perform detailed parsing of SQL (i.e. SELECT, INSERT, UPDATE, etc....) statements.
*
*/
package org.modeshape.sequencer.ddl;