Instantiate a PostgreSQL client from the current R or S-Plus session

Description

This function creates and initializes a PostgreSQL client. It returns an driver object that allows you to connect to one or several PostgreSQL servers.

Usage

PostgreSQL(max.con = 16, fetch.default.rec = 500, force.reload = FALSE)

Arguments

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.

Value

An object PostgreSQLDriver that extends dbDriver and dbObjectId. This object is required to create connections to one or several PostgreSQL database engines.

Side Effects

The R/S-Plus client part of the database communication is initialized, but note that connecting to the database engine needs to be done through calls to dbConnect.

User authentication

The passed string can be empty to use all default parameters, or it can contain one or more parameter settings separated by comma. Each parameter setting is in the form parameter = "value". Spaces around the equal sign are optional.

The most important parameters are user, password, host, dbname, port, tty and options.

References

See https://cran.r-project.org/package=DBI for more details on the R/S-Plus database interface.

See the documentation at the PostgreSQL Web site https://www.postgresql.org for details.

Author(s)

David A. James

See Also

On database managers:

dbDriver dbUnloadDriver

On connections, SQL statements and resultSets:

dbConnect dbDisconnect dbSendQuery dbGetQuery fetch dbClearResult

On transaction management:

dbCommit dbRollback

On meta-data:

summary dbGetInfo dbGetDBIVersion dbListTables dbListConnections dbListResults dbColumnInfo dbGetException dbGetStatement dbHasCompleted dbGetRowCount dbGetRowsAffected

Examples

## Not run: 
# create a PostgreSQL instance and create one connection.
> m <- dbDriver("PostgreSQL")
<PostgreSQLDriver:(4378)>

> con <- dbConnect(m, user="username", password="passwd", dbname="database_name")
> rs <- dbSendQuery(con, "select * sales where price < 10")
> df <- fetch(rs, n = 50)
> dbHasCompleted(rs)
[1] FALSE
> df2 <- fetch(rs, n = -1)
> dbHasCompleted(rs)
[1] TRUE
> dbClearResult(rs)
> dbListTables(con)    

## End(Not run)

Class PostgreSQLConnection

Description

PostgreSQLConnection class.

Generators

The method dbConnect is the main generator.

Extends

Class "DBIConnection", directly. Class "PostgreSQLObject", directly. Class "DBIObject", by class "DBIConnection". Class "dbObjectId", by class "PostgreSQLObject".

Methods

coerce

signature(from = "PostgreSQLConnection", to = "PostgreSQLResult"): ...

dbBegin

signature(conn = "PostgreSQLConnection"): ...

dbCallProc

signature(conn = "PostgreSQLConnection"): ...

dbCommit

signature(conn = "PostgreSQLConnection"): ...

dbConnect

signature(drv = "PostgreSQLConnection"): ...

dbDisconnect

signature(conn = "PostgreSQLConnection"): ...

dbExistsTable

signature(conn = "PostgreSQLConnection", name = "character"): ...

dbGetException

signature(conn = "PostgreSQLConnection"): ...

dbGetInfo

signature(dbObj = "PostgreSQLConnection"): ...

dbGetQuery

signature(conn = "PostgreSQLConnection", statement = "character"): ...

dbListFields

signature(conn = "PostgreSQLConnection", name = "character"): ...

dbListResults

signature(conn = "PostgreSQLConnection"): ...

dbListTables

signature(conn = "PostgreSQLConnection"): ...

dbReadTable

signature(conn = "PostgreSQLConnection", name = "character"): ...

dbRemoveTable

signature(conn = "PostgreSQLConnection", name = "character"): ...

dbRollback

signature(conn = "PostgreSQLConnection"): ...

dbSendQuery

signature(conn = "PostgreSQLConnection", statement = "character"): ...

dbWriteTable

signature(conn = "PostgreSQLConnection", name = "character", value = "data.frame"): ...

summary

signature(object = "PostgreSQLConnection"): ...

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://developer.r-project.org/db/.

See Also

DBI base classes:

DBIObject-class DBIDriver-class DBIConnection-class DBIResult-class

PostgreSQL classes:

PostgreSQLObject-class PostgreSQLDriver-class PostgreSQLConnection-class PostgreSQLResult-class

Examples

## Not run: 
drv <- dbDriver("PostgreSQL)
con <- dbConnect(drv, dbname = "template1")

## End(Not run)

Class PostgreSQLDriver

Description

An PostgreSQL driver implementing the R/S-Plus database (DBI) API.

Generators

The main generators are dbDriver and PostgreSQL.

Extends

Class "DBIDriver", directly. Class "PostgreSQLObject", directly. Class "DBIObject", by class "DBIDriver". Class "dbObjectId", by class "PostgreSQLObject".

Methods

coerce

signature(from = "PostgreSQLObject", to = "PostgreSQLDriver"): ...

dbConnect

signature(drv = "PostgreSQLDriver"): ...

dbGetInfo

signature(dbObj = "PostgreSQLDriver"): ...

dbListConnections

signature(drv = "PostgreSQLDriver"): ...

dbUnloadDriver

signature(drv = "PostgreSQLDriver"): ...

summary

signature(object = "PostgreSQLDriver"): ...

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://developer.r-project.org/db/.

See Also

DBI base classes:

DBIObject-class DBIDriver-class DBIConnection-class DBIResult-class

PostgreSQL classes:

PostgreSQLObject-class PostgreSQLDriver-class PostgreSQLConnection-class PostgreSQLResult-class

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname="template1")

## End(Not run)

Class PostgreSQLObject

Description

Base class for all PostgreSQL-specific DBI classes

Objects from the Class

A virtual Class: No objects may be created from it.

Extends

Class "DBIObject", directly. Class "dbObjectId", directly.

Methods

coerce

signature(from = "PostgreSQLObject", to = "PostgreSQLriver"): ...

dbDataType

signature(dbObj = "PostgreSQLObject"): ...

isSQLKeyword

signature(dbObj = "PostgreSQLObject", name = "character"): ...

make.db.names

signature(dbObj = "PostgreSQLObject", snames = "character"): ...

SQLKeywords

signature(dbObj = "PostgreSQLObject"): ...

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://developer.r-project.org/db/.

See Also

DBI base classes:

DBIObject-class DBIDriver-class DBIConnection-class DBIResult-class

PostgreSQL classes:

PostgreSQLObject-class PostgreSQLDriver-class PostgreSQLConnection-class PostgreSQLResult-class

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "template1")

## End(Not run)

Class PostgreSQLResult

Description

PostgreSQL's query results class. This classes encapsulates the result of an SQL statement (either select or not).

Generators

The main generator is dbSendQuery.

Extends

Class "DBIResult", directly. Class "PostgreSQLObject", directly. Class "DBIObject", by class "DBIResult". Class "dbObjectId", by class "PostgreSQLObject".

Methods

coerce

signature(from = "PostgreSQLConnection", to = "PostgreSQLResult"): ...

dbClearResult

signature(res = "PostgreSQLResult"): ...

dbColumnInfo

signature(res = "PostgreSQLResult"): ...

dbGetException

signature(conn = "PostgreSQLResult"): ...

dbGetInfo

signature(dbObj = "PostgreSQLResult"): ...

dbGetRowCount

signature(res = "PostgreSQLResult"): ...

dbGetRowsAffected

signature(res = "PostgreSQLResult"): ...

dbGetStatement

signature(res = "PostgreSQLResult"): ...

dbHasCompleted

signature(res = "PostgreSQLResult"): ...

dbListFields

signature(conn = "PostgreSQLResult", name = "missing"): ...

fetch

signature(res = "PostgreSQLResult", n = "numeric"): ...

fetch

signature(res = "PostgreSQLResult", n = "missing"): ...

summary

signature(object = "PostgreSQLResult"): ...

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://developer.r-project.org/db/

See Also

DBI base classes:

DBIObject-class DBIDriver-class DBIConnection-class DBIResult-class

PostgreSQL classes:

PostgreSQLObject-class PostgreSQLDriver-class PostgreSQLConnection-class PostgreSQLResult-class

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "template1")
## rs is the result set
rs <- dbSendQuery(con,"select * from sales")
## display the first three values of result set
fetch(rs,n=3)

## End(Not run)

R compatibility with S version 4/Splus5+ support functions

Description

These objects ease the task of porting functions into R from S Version 4 and S-Plus 5.0 and later. See the documentation there. May be obsolete in the future.

Usage

usingR(major, minor)

Examples

## Not run: 
rc <- try(fetch(res, n = -1))
if(inherit(rc, ErrorClass))
   stop("could not fetch the data")

## End(Not run)

Apply R/S-Plus functions to remote groups of DBMS rows (experimental)

Description

Applies R/S-Plus functions to groups of remote DBMS rows without bringing an entire result set all at once. The result set is expected to be sorted by the grouping field.

Details

dbApply This generic is meant to handle somewhat gracefully(?) large amounts of data from the DBMS by bringing into R manageable chunks; the idea is that the data from individual groups can be handled by R, but not all the groups at the same time.

Currently, only the PostgreSQL driver implements a method (see the helper function postgresqlDBApply) for this generic function.

Value

A list with as many elements as there were groups in the result set.

See Also

PostgreSQL postgresqlDBApply dbSendQuery fetch

Examples

## Not run: 
## compute quantiles for each network agent
con <- dbConnect(PostgreSQL(), user= "user", password="passwd", dbname="sample")
rs <- dbSendQuery(con, 
             "select Agent, ip_addr, DATA from pseudo_data order by Agent")
out <- dbApply(rs, INDEX = "Agent", 
        FUN = function(x, grp) quantile(x$DATA, names=FALSE))

## End(Not run)

Apply R/S-Plus functions to remote groups of DBMS rows (experimental)

Description

Applies R/S-Plus functions to groups of remote DBMS rows without bringing an entire result set all at once. The result set is expected to be sorted by the grouping field.

Methods

res

a PostgreSQL result set (see dbSendQuery).

...

any additional arguments to be passed to FUN.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL postgresqlDBApply dbSendQuery fetch

Examples

## Not run: 
## compute quanitiles for each network agent
con <- dbConnect(PostgreSQL(), user="user", password="passwd",dbname="dbname")
rs <- dbSendQuery(con, 
             "select Agent, ip_addr, DATA from pseudo_data order by Agent")
out <- dbApply(rs, INDEX = "Agent", 
        FUN = function(x, grp) quantile(x$DATA, names=FALSE))

## End(Not run)

Call an SQL stored procedure

Description

Not yet implemented.

Methods

conn

a PostgreSQLConnection object.

...

additional arguments are passed to the implementing method.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbReadTable.

DBMS Transaction Management

Description

Transaction related commands. Start a transaction, commit or roll back the current transaction in an PostgreSQL connection. dbBegin starts a transaction. dbCommit and dbRollback commit and rollback the transaction, respectively.

Methods

conn

a PostgreSQLConnection object, as produced by the function dbConnect.

...

currently unused.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbBegin, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbReadTable.

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname="postgres")
dbGetQuery(con, "select count(*) from sales")

dbBegin(con)
rs <- dbSendQuery(con, 
      "Delete * from sales as p where p.cost>10")
if(dbGetInfo(rs, what = "rowsAffected") > 250){
  warning("Rolling back transaction")
  dbRollback(con)
}else{
  dbCommit(con)
}

dbGetQuery(con, "select count(*) from sales")
dbDisconnect(con)

## End(Not run)

Create a connection object to an PostgreSQL DBMS

Description

These methods are straight-forward implementations of the corresponding generic functions.

Methods

drv

an object of class PostgreSQLDriver, or the character string "PostgreSQL" or an PostgreSQLConnection.

conn

an PostgreSQLConnection object as produced by dbConnect.

host

Name or the numeric IPaddress of the host to connect to. If address is specified, it should be in the standard IPv4 address format, e.g., 172.28.40.9 or if your machine supports IPv6, you can also use those addresses. The default is to connect to localhost by a UNIX domain socket.

dbname

The database name. Defaults to "", which is interpreted as PostgreSQL default. Most parameters are currently passed to PQsetdbLogin() as is. If dbname contains an = sign or has a valid connection URI prefix, it is taken as a conninfo for PQconnectdb() depending on the linked driver version. Refer to https://www.postgresql.org/docs/current/libpq-connect.html for detail.

user

PostgreSQL user name to connect as. Defaults to be the same as the operating system name of the user running the application.

password

Password to be used if the server demands password authentication.

port

Port number to connect to at the server host.

tty

Ignored (formerly, this specified where to send server debug output).

options

Command-line options to be sent to the server.

forceISOdate

logical if the communication of date (time stamp) from PostgreSQL is forced to ISO style at conection. This is an exception that is not really set by an option for PQsetdbLogin, but by issueing dbGetQuery(con, "set datestyle to ISO") after connection.

Side Effects

A connection between R/S-Plus and an PostgreSQL server is established. The current implementation supports up to 100 simultaneous connections.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbReadTable.

Examples

## Not run: 
# create an PostgreSQL instance and create one connection.
drv <- dbDriver("PostgreSQL")

# open the connection using user, passsword, etc., as
con <- dbConnect(drv, dbname = "postgres")

df <- dbGetQuery(con, statement = paste(
                      "SELECT itemCode, itemCost, itemProfit",
                      "FROM sales",
                      "SORT BY itemName"));
# Run an SQL statement by creating first a resultSet object
rs <- dbSendQuery(con, statement = paste(
                      "SELECT itemCode, itemCost, itemProfit",
                      "FROM sales",
                      "SORT BY itemName"));

# we now fetch records from the resultSet into a data.frame
df <- fetch(rs, n = -1)   # extract all rows
dim(df)

## End(Not run)

Determine the SQL Data Type of an S object

Description

This method is a straight-forward implementation of the corresponding generic function.

Methods

dbObj

any PostgreSQLObject object, e.g., PostgreSQLDriver, PostgreSQLConnection, PostgreSQLResult.

obj

R/S-Plus object whose SQL type we want to determine.

...

any other parameters that individual methods may need.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

isSQLKeyword make.db.names

Examples

## Not run: 
data(quakes)
drv <- dbDriver("PostgreSQL")
sql.type <- dbDataType(drv, quakes)

## End(Not run)

PostgreSQL implementation of the Database Interface (DBI) classes and drivers

Description

PostgreSQL driver initialization and closing

Methods

drvName

character name of the driver to instantiate.

drv

an object that inherits from PostgreSQLDriver as created by dbDriver.

max.con

optional integer requesting the maximum number of simultanous connections (may be up to 100)

.

fetch.default.rec

default number of records to retrieve per fetch. Default is 500. This may be overridden in calls to fetch with the n= argument.

force.reload

optional logical used to force re-loading or recomputing the size of the connection table. Default is FALSE.

...

currently unused.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbListTables, dbReadTable.

Examples

## Not run: 

# create an PostgreSQL instance and set 10000 of rows per fetch.
library(RPostgreSQL)
drv <- dbDriver("PostgreSQL", fetch.default.records=10000)

# Connecting to PostgreSQL with the specified parameters
con <- dbConnect(drv,user="usrname",password="passwd",dbname="postgres")

# Running the query to obtain the resultset
rs <- dbSendQuery(con, "select * from cities where population > 5000")

# fetch records into a dataframe.
# n = 50 fetched fifty records
df <- fetch(rs, n = 50)
# n = -1 fetches all the remaining records available
df2 <- fetch(rs, n = -1)

# Clearing the result set
dbClearResult(rs)

#This returns a character vector (possibly of zero-length)
# table names available on the con connection.
dbListTables(con)

## End(Not run)

Database interface meta-data

Description

These methods are straight-forward implementations of the corresponding generic functions.

Methods

dbObj

any object that implements some functionality in the R/S-Plus interface to databases (a driver, a connection or a result set).

res

an PostgreSQLResult.

...

currently not being used.

Note

nullOk in dbColumnInfo was changed. Now it may be TRUE, FALSE, or NA; the column may be totally deleted in future releases;

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbDriver, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbListTables, dbReadTable.

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, user= "user", password="password", dbname="sample")

dbListTables(con)

rs <- dbSendQuery(con, query.sql)
dbGetStatement(rs)
dbHasCompleted(rs)

info <- dbGetInfo(rs)
names(dbGetInfo(drv))

# DBIConnection info
names(dbGetInfo(con))

# DBIResult info
names(dbGetInfo(rs)) 

## End(Not run)

List items from an PostgreSQL DBMS and from objects

Description

These methods are straight-forward implementations of the corresponding generic functions.

Methods

drv

an PostgreSQLDriver.

conn

an PostgreSQLConnection.

name

a character string with the table name.

...

currently not used.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbGetInfo, dbColumnInfo, dbDriver, dbConnect, dbSendQuery

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
# after working awhile...
for(con in dbListConnections(drv)){
   dbGetStatement(dbListResults(con))
}

## End(Not run)

Class dbObjectId

Description

A helper (mixin) class to provide external references in an R/S-Plus portable way.

Objects from the Class

A virtual Class: No objects may be created from it.

Slots

Id:

Object of class "integer" this is an integer vector holding an opaque reference into a C struct (may or may not be a C pointer, may or may not have length one).

Methods

coerce

signature(from = "dbObjectId", to = "integer"): ...

coerce

signature(from = "dbObjectId", to = "numeric"): ...

coerce

signature(from = "dbObjectId", to = "character"): ...

format

signature(x = "dbObjectId"): ...

print

signature(x = "dbObjectId"): ...

show

signature(object = "dbObjectId"): ...

Note

A cleaner mechanism would use external references, but historically this class has existed mainly for R/S-Plus portability.

Examples

## Not run: 
  pg <- dbDriver("PostgreSQL")
  con <- dbConnect(pg, "user", "password")
  is(pg, "dbObjectId")   ## True
  is(con, "dbObjectId")  ## True
  isPostgresqlIdCurrent(con)       ## True
  q("yes")
  \$ R 
  isPostgresqlIdCurrent(con)       ## False

## End(Not run)

Convenience functions for Importing/Exporting DBMS tables

Description

These functions mimic their R/S-Plus counterpart get, assign, exists, remove, and objects, except that they generate code that gets remotely executed in a database engine.

Value

A data.frame in the case of dbReadTable; otherwise a logical indicating whether the operation was successful.

Methods

conn

an PostgreSQLConnection database connection object.

name

a character string specifying a table name.

value

a data.frame (or coercible to data.frame).

When the value is a character string, it is assumed to be a file name containing the data to be loaded; The implementation is INCOMPLETE and should not be used in current state.

row.names

UNTESTED;

in the case of dbReadTable, this argument can be a string or an index specifying the column in the DBMS table to be used as row.names in the output data.frame (a NULL, "", or 0 specifies that no column should be used as row.names in the output).

In the case of dbWriteTable, this argument should be a logical specifying whether the row.names should be output to the output DBMS table; if TRUE, an extra field whose name will be whatever the R/S-Plus identifier "row.names" maps to the DBMS (see make.db.names).

overwrite

a logical specifying whether to overwrite an existing table or not. Its default is FALSE.

append

a logical specifying whether to append to an existing table in the DBMS. Its default is FALSE.

allow.keywords

dbWriteTable accepts a logical allow.keywords to allow or prevent PostgreSQL reserved identifiers to be used as column names. By default it is FALSE.

dots

optional arguments.

When dbWriteTable is used to import data from a file, you may optionally specify header=, row.names=, col.names=, sep=, eol=, field.types=, skip=, and quote=. NOT FULLY IMPLEMENTED YET.

header is a logical indicating whether the first data line (but see skip) has a header or not. If missing, it value is determined following read.table convention, namely, it is set to TRUE if and only if the first row has one fewer field that the number of columns.

row.names is a logical to specify whether the first column is a set of row names. If missing its default follows the read.table convention.

col.names a character vector with column names; column names are quoted to work as SQL identifiers. Thus, the column names are case sensitive and make.db.names will NOT be used here.

sep= specifies the field separator, and its default is ','.

eol= specifies the end-of-line delimiter, and its default is '\n'.

skip specifies number of lines to skip before reading the data, and it defaults to 0.

field.types is a list of named field SQL types where names(field.types) provide the new table's column names (if missing, field types are inferred using dbDataType).

Note

dbWriteTable creates additional column in the database, while dbReadTable reads that column by default. So, it is not symmetrical in its current implementation. the backend raw_names may change in future versions.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, isSQLKeyword, dbDriver, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbListTables, dbReadTable.

Examples

## Not run: 
conn <- dbConnect("PostgreSQL", dbname = "wireless")
if(dbExistsTable(conn, "frame_fuel")){
   dbRemoveTable(conn, "frame_fuel")
   dbWriteTable(conn, "frame_fuel", fuel.frame)
}
if(dbExistsTable(conn, "RESULTS")){
   dbWriteTable(conn, "RESULTS", results2000, append = T)
else
   dbWriteTable(conn, "RESULTS", results2000)
}

## End(Not run)

Execute a statement on a given database connection

Description

These methods are straight-forward implementations of the corresponding generic functions. However, for complex data like array are just transferred as a string instead of the corresponding vector in R. This behavior will change in future releases, and the author is advised not to rely on it.

Methods

conn

an PostgreSQLConnection object.

statement

a character vector of length 1 with the SQL statement.

res

an PostgreSQLResult object.

...

additional parameters.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbDriver, dbConnect, fetch, dbCommit, dbGetInfo, dbReadTable.

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, "usr", "password", "dbname")
res <- dbSendQuery(con, "SELECT * from sales")
data <- fetch(res, n = -1)
# alternatively, use dbGetQuery
data <- dbGetQuery(con, "SELECT * from sales")

## End(Not run)

Set data mappings between PostgreSQL and R/S-Plus

Description

Not yet implemented

Methods

res

a PostgreSQLResult object as returned by dbSendQuery.

flds

a data.frame with field descriptions as returned by dbColumnInfo.

...

any additional arguments are passed to the implementing method.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbSendQuery, fetch, dbColumnInfo.

Examples

## Not run: 
makeImage <- function(x) {
  .C("make_Image", as.integer(x), length(x))
}

res <- dbSendQuery(con, statement)
flds <- dbColumnInfo(res)
flds[3, "Sclass"] <- makeImage

dbSetDataMappings(rs, flds)

im <- fetch(rs, n = -1)

## End(Not run)

Fetch records from a previously executed query

Description

This method is a straight-forward implementation of the corresponding generic function.

Details

The RPostgreSQL implementations retrieves only n records, and if n is missing it only returns up to fetch.default.rec as specified in the call to PostgreSQL (500 by default).

Methods

res

an PostgreSQLResult object.

n

maximum number of records to retrieve per fetch. Use n = -1 to retrieve all pending records; use a value of n = 0 for fetching the default number of rows fetch.default.rec defined in the PostgreSQL initialization invocation.

...

currently not used.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbConnect, dbSendQuery, dbGetQuery, dbClearResult, dbCommit, dbGetInfo, dbReadTable.

Examples

## Not run: 
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, user = "ruser",password = "123456",dbname = "status")
res <- dbSendQuery(con, statement = paste(
                      "SELECT w.category, w.cost, p.type",
                      "FROM items w, sales P",
                      "WHERE w.category = p.type",
                      "ORDER BY w.cost"))
# we now fetch the first 100 records from the resultSet into a data.frame
data1 <- fetch(res, n = 100)   
dim(data1)

dbHasCompleted(res)

# let's get all remaining records
data2 <- fetch(res, n = -1)

## End(Not run)

Check whether a database handle object is valid or not

Description

Support function that verifies that an object holding a reference to a foreign object is still valid for communicating with the RDBMS

Usage

isPostgresqlIdCurrent(obj)

Arguments

Details

dbObjects are R/S-Plus remote references to foreign objects. This introduces differences to the object's semantics such as persistence (e.g., connections may be closed unexpectedly), thus this function provides a minimal verification to ensure that the foreign object being referenced can be contacted.

Value

a logical scalar.

See Also

dbDriver dbConnect dbSendQuery fetch

Examples

## Not run: 
cursor <- dbSendQuery(con, sql.statement)
isIdCurrent(cursor)

## End(Not run)

Make R/S-Plus identifiers into quoted PostgreSQL identifiers

Description

Calls postgresqlquoteId to make valid quoted identifiers. This has calling convention same as the make.db.names for compatibility.

Methods

dbObj

any PostgreSQL object (e.g., PostgreSQLDriver). Just ignored.

snames

a character vector of R/S-Plus identifiers (symbols) from which we need to make SQL identifiers.

name

a character vector of SQL identifiers we want to check against keywords from the DBMS. Ignored.

unique

logical describing whether the resulting set of SQL names should be unique. Its default is TRUE. Following the SQL 92 standard, uniqueness of SQL identifiers is determined regardless of whether letters are upper or lower case. Ignored.

allow.keywords

logical describing whether SQL keywords should be allowed in the resulting set of SQL names. Its default is TRUE. Ignored.

keywords

a character vector with SQL keywords, by default it is .PostgreSQLKeywords define in RPostgreSQL. This may be overriden by users. Ignored.

case

a character string specifying whether to make the comparison as lower case, upper case, or any of the two. it defaults to any. Ignored.

...

currently not used.

References

The set of SQL keywords is stored in the character vector .SQL92Keywords and reflects the SQL ANSI/ISO standard as documented in "X/Open SQL and RDA", 1994, ISBN 1-872630-68-8. Users can easily override or update this vector.

PostgreSQL does add some keywords to the SQL 92 standard, they are listed in the .PostgreSQLKeywords object.

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbReadTable, dbWriteTable, dbExistsTable, dbRemoveTable, dbListTables.

Examples

## Not run: 
# This example shows how we could export a bunch of data.frames
# into tables on a remote database.


## End(Not run)

Build the SQL CREATE TABLE definition as a string

Description

Build the SQL CREATE TABLE definition as a string for the input data.frame

Usage

postgresqlBuildTableDefinition(dbObj, name, obj, 
	field.types = NULL, row.names = TRUE, ...)

Arguments

Details

The output SQL statement is a simple CREATE TABLE with suitable for dbGetQuery

Value

An SQL string

References

See the Database Interface definition document DBI.pdf in the base directory of this package or https://cran.r-project.org/package=DBI.

See Also

PostgreSQL, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbReadTable.

Apply R/S-Plus functions to remote groups of DBMS rows (experimental)

Description

Applies R/S-Plus functions to groups of remote DBMS rows without bringing an entire result set all at once. The result set is expected to be sorted by the grouping field.

Usage

postgresqlDBApply(res, INDEX, FUN = stop("must specify FUN"),
         begin = NULL, 
         group.begin =  NULL, 
         new.record = NULL, 
         end = NULL, 
         batchSize = 100, maxBatch = 1e6, 
         ..., simplify = TRUE)

Arguments

.

Details

dbApply This function is meant to handle somewhat gracefully(?) large amounts of data from the DBMS by bringing into R manageable chunks (about batchSize records at a time, but not more than maxBatch); the idea is that the data from individual groups can be handled by R, but not all the groups at the same time.

The PostgreSQL implementation postgresqlDBApply allows us to register R functions that get invoked when certain fetching events occur. These include the “begin” event (no records have been yet fetched), “begin.group” (the record just fetched belongs to a new group), “new record” (every fetched record generates this event), “group.end” (the record just fetched was the last row of the current group), “end” (the very last record from the result set). Awk and perl programmers will find this paradigm very familiar (although SAP's ABAP language is closer to what we're doing).

Value

A list with as many elements as there were groups in the result set.

Note

This is an experimental version implemented only in R (there are plans, time permitting, to implement it in S-Plus).

The terminology that we're using is closer to SQL than R. In R what we're referring to “groups” are the individual levels of a factor (grouping field in our terminology).

See Also

PostgreSQL, dbSendQuery, fetch.

Examples

## Not run: 
drv <- dbDriver(RPostgreSQL)
con <- dbConnect(drv, user ="usrname", password="pword", dname="database")
res <- dbSendQuery(con, 
             "select Agent, ip_addr, DATA from pseudo_data order by Agent")
out <- dbApply(res, INDEX = "Agent", 
        FUN = function(x, grp) quantile(x$DATA, names=FALSE))

## End(Not run)

Support Functions

Description

These functions are the workhorse behind the RPostgreSQL package, but users need not invoke these directly. For details see PostgreSQL.

Usage

   ## PostgreSQLDriver-related
   postgresqlInitDriver(max.con=16, fetch.default.rec = 500, force.reload=FALSE)
   postgresqlDriverInfo(obj, what, ...)
   postgresqlDescribeDriver(obj, verbose = FALSE, ...)
   postgresqlCloseDriver(drv, ...)

   ## PostgreSQLConnection-related
   postgresqlNewConnection(drv, user, password, host, dbname, port, 
			tty, options, forceISOdate = TRUE)
   postgresqlCloneConnection(con, ...)
   postgresqlConnectionInfo(obj, what, ...)
   postgresqlDescribeConnection(obj, verbose = FALSE, ...)
   postgresqlCloseConnection(con, ...)

   ## PostgreSQLResult-related
   postgresqlExecStatement(con, statement, params, ...)
   postgresqlFetch(res, n=0, ...)
   postgresqlQuickSQL(con, statement, ...)
   postgresqlResultInfo(obj, what, ...)
   postgresqlDescribeResult(obj, verbose = FALSE, ...)
   postgresqlCloseResult(res, ...)
   postgresqlDescribeFields(res, ...)

   ## data mappings, convenience functions, and extensions
   postgresqlDataType(obj, ...)
   postgresqlReadTable(con, name, row.names = "row.names", check.names = TRUE, ...)
   postgresqlWriteTable(con, name, value, field.types, row.names = TRUE,
      overwrite=FALSE, append=FALSE, ..., allow.keywords = FALSE)
   postgresqlpqExec(con, statement)
   postgresqlCopyIn(con, filename)
   postgresqlgetResult(con)
   postgresqlEscapeStrings(con, preescapedstring)
   postgresqlEscapeBytea(con, raw_data)
   postgresqlUnescapeBytea(escapedbytea)
   postgresqlQuoteId(identifiers)
   postgresqlTableRef(identifiers)
   postgresqlImportFile(con, name, value, field.types, overwrite=FALSE,
      append=FALSE, header, row.names, nrows=50, sep=",", eol="\n", 
      skip = 0, quote="\"", ...)

   ## Transaction Management
   postgresqlTransactionStatement(con, statement)

Arguments

Value

postgresqlInitDriver returns an PostgreSQLDriver object.

postgresqlDriverInfo returns a list of name-value metadata pairs.

postgresqlDescribeDriver returns NULL (displays the object's metadata).

postgresqlCloseDriver returns a logical indicating whether the operation succeeded or not.

postgresqlNewConnection returns an PostgreSQLConnection object.

postgresqlCloneConnection returns an PostgreSQLConnection object.

postgresqlConnectionInforeturns a list of name-value metadata pairs.

postgresqlDescribeConnection returns NULL (displays the object's metadata).

postgresqlCloseConnection returns a logical indicating whether the operation succeeded or not.

postgresqlExecStatement returns an PostgreSQLResult object.

postgresqlFetch returns a data.frame.

postgresqlQuickSQL returns either a data.frame if the statement is a select-like or NULL otherwise.

postgresqlDescribeResult returns NULL (displays the object's metadata).

postgresqlCloseResult returns a logical indicating whether the operation succeeded or not.

postgresqlDescribeFields returns a data.frame with one row per field with columns name, Sclass, type, len, precision, scale, and nullOK which fully describe each field in a result set. Except for Sclass (which shows the mapping of the field type into an R/S-Plus class) all the information pertains to PostgreSQL's data storage attributes.

postgresqlReadTable returns a data.frame with the contents of the DBMS table.

postgresqlWriteTable returns a logical indicating whether the operation succeeded or not.

postgresqlpqExec returns NUL (executes the statement but does not try to get result. This is called internally from postgresqlWriteTable before postgresqlCopyInDataframe

postgresqlCopyIn returns NULL (copies the content of the file through the socket connection to postgresql backend. This should be used just after COPY tablename FROM STDIN query. This is not used now.)

postgresqlCopyInDataframe returns NULL (copies the content of the dataframe through the socket connection to postgresql backend. Strings are encoded as UTF-8 for transfer. The client_encoding should be set to UTF-8. This should be used just after COPY tablename FROM STDIN query.)

postgresqlgetResult returns an PostgreSQLResult object. This is called after completion of execution of postgresqlpqExec.

postgresqlEscapeStrings returns a character string which is escaped properly so that it can be surrounded with a single quote and used as literal in SQL. The escape procedure is dependent on the character encoding of the connection.

postgresqlEscapeBytea returns a character string which represents the raw data proper escape so that it can be surrounded with a single quote and used as literal in SQL. Note that on 8.X connection E prefix should exist before the first quote. However this changes the behaviour in 9.0, where the E should not exist.

postgresqlUnescapeBytea returns a raw data specified by the character string. The character string should contain the 'escaped' bytea or hex encoded bytea that was output from the database server.

postgresqlQuoteId returns a character string which is quoted as identifier. Returns vector on vector arguemnt.

postgresqlTableRef returns a character string which is quoted as identifier. Reterns a charcter string concatenated with "." so that "dbname"."schemaname"."tablename" reference is created upon c("dbname", "schemaname", "tablename") arguemnt.

postgresqlDataType retuns a character string with the closest

postgresqlResultInfo returns a list of name-value metadata pairs.

postgresqlTransactionStatement returns a logical indicating whether the operation succeeded or not.

Constants

.PostgreSQLPkgName (currently "RPostgreSQL"), .PostgreSQLPkgVersion (the R package version), .PostgreSQLPkgRCS (the RCS revision), .PostgreSQL.NA.string (character that PostgreSQL uses to denote NULL on input), .PostgreSQLSQLKeywords (a lot!) .conflicts.OK.

Summarize an PostgreSQL object

Description

These methods are straight-forward implementations of the corresponding generic functions.

Methods

object = "DBIObject"

Provides relevant metadata information on object, for instance, the PostgreSQL server file, the SQL statement associated with a result set, etc.

from

object to be coerced

to

coercion class

x

object to format or print or show