-
Notifications
You must be signed in to change notification settings - Fork 111
/
MySQL.Rd
176 lines (162 loc) · 5.16 KB
/
MySQL.Rd
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
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
% $Id$
\name{MySQL}
\alias{MySQL}
\title{
Instantiate a MySQL client from the current R session
}
\description{
This function creates and initializes a MySQL client.
It returns an driver object that allows you to connect
to one or several MySQL servers.
}
\usage{
MySQL(max.con = 16, fetch.default.rec = 500, force.reload = FALSE)
}
\arguments{
\item{max.con }{
maximum number of connections that are intended to have open at one time.
There's no intrinic limit, since strictly speaking this limit applies
to MySQL \emph{servers}, but clients can have (at least in theory)
more than this. Typically there are at most a handful of open connections,
thus the internal \code{RMySQL} code uses a very simple linear search
algorithm to manage its connection table.
}
\item{fetch.default.rec}{
number of records to fetch at one time from the database.
(The \code{\link[DBI]{fetch}} method uses this number as a default.)
}
\item{force.reload}{
should the client code be reloaded (reinitialize)?
Setting this to \code{TRUE} allows you to change
default settings. Notice that all connections should be closed
before re-loading.
}
}
\value{
An object \code{MySQLDriver} that extends
\code{dbDriver} and
\code{dbObjectId}.
This object is required to create connections
to one or several MySQL database engines.
}
\section{Side Effects}{
The R client part of the database communication is initialized,
but note that connecting to the database engine needs to be done through
calls to \code{\link[DBI]{dbConnect}}.
}
\details{
This object is a singleton, that is, on subsequent invocations
it returns the same initialized object.
This implementation allows you to connect
to multiple host servers and run multiple connections on each server
simultaneously.
}
\section{User authentication}{
The preferred method to pass authentication parameters to the
server (e.g., user, password, host) is through the MySQL personal
configuration file \file{\$HOME/.my.cnf} (or \file{c:/my.cnf} under Windows).
Since specifying passwords on calls to
\code{dbConnect}
is a very bad idea (and so is specifying passwords through
shell variables),
the client code parses the configuration file \file{\$HOME/.my.cnf};
this file consists of zero or more sections, each starting with a
line of the form \code{[section-name]}, for instance
\$ cat \$HOME/.my.cnf\cr
\# this is a comment\cr
[client]\cr
user = dj\cr
host = localhost\cr
\cr
[rs-dbi]\cr
database = s-data\cr
\cr
[lasers]\cr
user = opto\cr
database = opto\cr
password = pure-light\cr
host = merced\cr
...\cr
[iptraffic]\cr
host = data\cr
database = iptraffic\cr
\cr
This file should be readeable only by you.
Inside each section, MySQL parameters may be specified one per line
(e.g., \code{user = opto}).
MySQL always considers default options from the \code{[client]} group
for connecting to a server. To override or add additional options, R MySQL
combines default options from the \code{[rs-dbi]} group, but you may specifiy you own
group in the \code{dbConnect} call to tailor your environment. Note that
to override options, you must place your group after the \code{[client]} group
in configuration file.
For instance, if you define a group, say, \code{[iptraffic]},
then instead of including all these parameters in the
call to \code{dbConnect}, you simply supply the
name of the \code{group},
e.g., \code{dbConnect(mgr, group = "iptraffic")}.
The most important parameters are \code{user},
\code{password}, \code{host},
and \code{dbname}.
}
\note{
Use the option \code{database} in place of\code{dbname} in configuration files.
}
\author{David A. James}
\section{References}{
See \url{stat.bell-labs.com/RS-DBI}
for more details on the R/S-Plus database interface.
See the documentation at the MySQL Web site
\url{http://www.mysql.com} for details.
}
\seealso{
On database managers:
\code{\link[DBI]{dbDriver}}
\code{\link[DBI]{dbUnloadDriver}}
On connections, SQL statements and resultSets:
\code{\link[DBI]{dbConnect}}
\code{\link[DBI]{dbDisconnect}}
\code{\link[DBI]{dbSendQuery}}
\code{\link[DBI]{dbGetQuery}}
\code{\link[DBI]{fetch}}
\code{\link[DBI]{dbClearResult}}
On transaction management:
\code{\link[DBI]{dbCommit}}
\code{\link[DBI]{dbRollback}}
On meta-data:
\code{\link{summary}}
\code{\link[DBI]{dbGetInfo}}
\code{\link[DBI]{dbGetDBIVersion}}
\code{\link[DBI]{dbListTables}}
\code{\link[DBI]{dbListConnections}}
\code{\link[DBI]{dbListResults}}
\code{\link[DBI]{dbColumnInfo}}
\code{\link[DBI]{dbGetException}}
\code{\link[DBI]{dbGetStatement}}
\code{\link[DBI]{dbHasCompleted}}
\code{\link[DBI]{dbGetRowCount}}
}
\examples{\dontrun{
# create a MySQL instance and create one connection.
> m <- dbDriver("MySQL")
<MySQLDriver:(4378)>
# open the connection using user, passsword, etc., as
# specified in the "[iptraffic]" section of the
# configuration file \file{\$HOME/.my.cnf}
> con <- dbConnect(m, group = "iptraffic")
> rs <- dbSendQuery(con, "select * from HTTP_ACCESS where IP_ADDRESS = '127.0.0.1'")
> df <- fetch(rs, n = 50)
> dbHasCompleted(rs)
[1] FALSE
> df2 <- fetch(rs, n = -1)
> dbHasCompleted(rs)
[1] TRUE
> dbClearResult(rs)
> dim(dbGetQuery(con, "show tables"))
[1] 74 1
> dbListTables(con)
}
}
\keyword{interface}
\keyword{database}
% vim: syntax=tex