blob: ebb5b1f235a30db54ecf3e2e66c9264c37ab330f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
|
/* Copyright (C) 2003 MySQL AB
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
(at your option) 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 */
/**
@mainpage NDB ODBC
The ODBC Driver Frontend has:
-# HandleBase : Various ODBC handles
-# AttrArea : Attributes of handles
-# ConnArea : Communication area on connection level between driver parts
-# StmtArea : Communication area on statement level between driver parts
and controls the following steps:
-# SQL_compiler : Compiles SQL into SQL_code_tree:s
-# Parser : Bison grammar
-# Analyzer : Syntactic and semantic checks (binds names)
-# PlanGen : Generate initial (execution) plan (PlanTree)
-# CodeGen : Generates CodeTree:s out of PlanTree:s
-# Optimizer : Optimizes PlanTree:s
-# Output : Outputs executable CodeTree:s
-# Executor : Executes CodeTree:s
-# CodeTree::allocRun : Allocates runtime data structures (RunTree:s)
-# Dataflow machine : Executes and evaluates statement and expressions
The Dataflow machine works in four different ways:
-# Non-query statements
-# CodeStmt::execute : Executes (non-query) statement
-# Query statements
-# CodeQuery::execute : Execute Query statement
-# CodeQuery::fetch : Fetch row from CodeQuery node
-# Boolean expressions
-# CodePred::evaluate : Evaluates boolean expression
-# Arithmetical expressions
-# CodeExpr::evaluate : Evaluates arithmetic expression
The following components are used throughout the NDB ODBC:
-# Context (Ctx) : Info regarding execution/evaluation
-# Diagnostic area (DiagArea) : Errors and warnings (for ODBC user)
-# DescArea : Description of ODBC user input/output bind varibles/columns
-# Dictionary (DictBase) : Lookup info stored in NDB Dictionary
and info regarding temporary
materialized results
-# ResultArea : Execution (temporary) results
@section secCompiler SQL_compiler : SQL to SQL_code_tree
The SQL_compiler takes an <em>SQL statement</em> and translates
it into an SQL_code_tree. The compiler uses an SQL_code_tree
internally during the compilation and the result of the compilation
is a simlified SQL_code_tree.
The compiler works in the following steps:
-# Parse SQL statments and create SQL_code_tree representing the
statement.
-# Apply Syntax Rules to the SQL_code_tree. Syntax rules are
rules which are <em>not</em> expressed in the SQL grammar,
but are expressed in natural language in the SQL specification.
-# Apply Access Rules to the SQL_code_tree
(this is not implemented, since NDB Cluster has no access control)
-# Apply General Rules to the SQL_code_tree
-# Apply Conformance Rules to the SQL_code_tree
The resulting simplified SQL_code_tree is represented by a
tree of C++ objects.
@section secCodegen Codegen : SQL_code_tree to CodeTree
CodeGen takes simplified SQL_code_tree:s and transforms them into
CodeTree:s.
@section secOptimizer Optimizer : CodeTree to CodeTree
The implementation of the ODBC optimizer will uses the
PlanTree:s to represent statements and transforms them
into executable format (still PlanTree format).
@note In the future, more optimizations can be implemented.
@section secExecutor Executor : Execute CodeTree
The Executor uses the following data structures:
-# CodeTree : A read-only quary evaluation plan
-# RunTree : Runtime data structures containing ResultSet:s
The execution mechanism is actually implemented as a
part of the CodeTree.
*/
|
