#------------------------------------------------------- # # $Id: Pg.pm,v 1.8 1998/09/27 19:12:22 mergl Exp $ # # Copyright (c) 1997, 1998 Edmund Mergl # #------------------------------------------------------- package Pg; #use strict; use Carp; use vars qw($VERSION @ISA @EXPORT $AUTOLOAD); require Exporter; require DynaLoader; require AutoLoader; require 5.002; @ISA = qw(Exporter DynaLoader); # Items to export into callers namespace by default. @EXPORT = qw( PQconnectdb PQsetdbLogin PQsetdb PQconndefaults PQfinish PQreset PQrequestCancel PQdb PQuser PQpass PQhost PQport PQtty PQoptions PQstatus PQerrorMessage PQsocket PQbackendPID PQtrace PQuntrace PQexec PQnotifies PQsendQuery PQgetResult PQisBusy PQconsumeInput PQgetline PQputline PQgetlineAsync PQputnbytes PQendcopy PQmakeEmptyPGresult PQresultStatus PQntuples PQnfields PQbinaryTuples PQfname PQfnumber PQftype PQfsize PQfmod PQcmdStatus PQoidStatus PQcmdTuples PQgetvalue PQgetlength PQgetisnull PQclear PQprint PQdisplayTuples PQprintTuples PQlo_open PQlo_close PQlo_read PQlo_write PQlo_lseek PQlo_creat PQlo_tell PQlo_unlink PQlo_import PQlo_export PGRES_CONNECTION_OK PGRES_CONNECTION_BAD PGRES_EMPTY_QUERY PGRES_COMMAND_OK PGRES_TUPLES_OK PGRES_COPY_OUT PGRES_COPY_IN PGRES_BAD_RESPONSE PGRES_NONFATAL_ERROR PGRES_FATAL_ERROR PGRES_INV_SMGRMASK PGRES_INV_ARCHIVE PGRES_INV_WRITE PGRES_INV_READ PGRES_InvalidOid ); $Pg::VERSION = '1.8.0'; sub AUTOLOAD { # This AUTOLOAD is used to 'autoload' constants from the constant() # XS function. If a constant is not found then control is passed # to the AUTOLOAD in AutoLoader. my $constname; ($constname = $AUTOLOAD) =~ s/.*:://; my $val = constant($constname, @_ ? $_[0] : 0); if ($! != 0) { if ($! =~ /Invalid/) { $AutoLoader::AUTOLOAD = $AUTOLOAD; goto &AutoLoader::AUTOLOAD; } else { croak "Your vendor has not defined Pg macro $constname"; } } eval "sub $AUTOLOAD { $val }"; goto &$AUTOLOAD; } bootstrap Pg $VERSION; sub doQuery { my $conn = shift; my $query = shift; my $array_ref = shift; my ($result, $status, $i, $j); if ($result = $conn->exec($query)) { if (2 == ($status = $result->resultStatus)) { for $i (0..$result->ntuples - 1) { for $j (0..$result->nfields - 1) { $$array_ref[$i][$j] = $result->getvalue($i, $j); } } } } return $status; } 1; __END__ =head1 NAME Pg - Perl5 extension for PostgreSQL =head1 SYNOPSIS new style: use Pg; $conn = Pg::connectdb("dbname=template1"); $result = $conn->exec("create database pgtest"); old style (depreciated): use Pg; $conn = PQsetdb('', '', '', '', template1); $result = PQexec($conn, "create database pgtest"); PQclear($result); PQfinish($conn); =head1 DESCRIPTION The Pg module permits you to access all functions of the Libpq interface of PostgreSQL. Libpq is the programmer's interface to PostgreSQL. Pg tries to resemble this interface as close as possible. For examples of how to use this module, look at the file test.pl. For further examples look at the Libpq applications in ../src/test/examples and ../src/test/regress. You have the choice between the old C-style and a new, more Perl-ish style. The old style has the benefit, that existing Libpq applications can be ported to perl just by prepending every variable with a '$'. The new style uses class packages and might be more familiar for C++-programmers. =head1 GUIDELINES =head2 new style The new style uses blessed references as objects. After creating a new connection or result object, the relevant Libpq functions serve as virtual methods. One benefit of the new style: you do not have to care about freeing the connection- and result-structures. Perl calls the destructor whenever the last reference to an object goes away. The method fetchrow can be used to fetch the next row from the server: while (@row = $result->fetchrow). Columns which have NULL as value will be set to C. =head2 old style All functions and constants are imported into the calling packages name-space. In order to to get a uniform naming, all functions start with 'PQ' (e.g. PQlo_open) and all constants start with 'PGRES_' (e.g. PGRES_CONNECTION_OK). There are two functions, which allocate memory, that has to be freed by the user: PQsetdb, use PQfinish to free memory. PQexec, use PQclear to free memory. Pg.pm contains one convenience function: doQuery. It fills a two-dimensional array with the result of your query. Usage: Pg::doQuery($conn, "select attr1, attr2 from tbl", \@ary); for $i ( 0 .. $#ary ) { for $j ( 0 .. $#{$ary[$i]} ) { print "$ary[$i][$j]\t"; } print "\n"; } Notice the inner loop ! =head1 CAVEATS There are few exceptions, where the perl-functions differs from the C-counterpart: PQprint, PQnotifies and PQconndefaults. These functions deal with structures, which have been implemented in perl using lists or hash. =head1 FUNCTIONS The functions have been divided into three sections: Connection, Result, Large Objects. For details please read L. =head2 1. Connection With these functions you can establish and close a connection to a database. In Libpq a connection is represented by a structure called PGconn. When opening a connection a given database name is always converted to lower-case, unless it is surrounded by double quotes. All unspecified parameters are replaced by environment variables or by hard coded defaults: parameter environment variable hard coded default -------------------------------------------------- host PGHOST localhost port PGPORT 5432 options PGOPTIONS "" tty PGTTY "" dbname PGDATABASE current userid user PGUSER current userid password PGPASSWORD "" Using appropriate methods you can access almost all fields of the returned PGconn structure. $conn = Pg::setdbLogin($pghost, $pgport, $pgoptions, $pgtty, $dbname, $login, $pwd) Opens a new connection to the backend. The connection identifier $conn ( a pointer to the PGconn structure ) must be used in subsequent commands for unique identification. Before using $conn you should call $conn->status to ensure, that the connection was properly made. $conn = Pg::setdb($pghost, $pgport, $pgoptions, $pgtty, $dbname) The method setdb should be used when username/password authentication is not needed. $conn = Pg::connectdb("option1=value option2=value ...") Opens a new connection to the backend using connection information in a string. Possible options are: host, port, options, tty, dbname, user, password. The connection identifier $conn (a pointer to the PGconn structure) must be used in subsequent commands for unique identification. Before using $conn you should call $conn->status to ensure, that the connection was properly made. $Option_ref = Pg::conndefaults() while(($key, $val) = each %$Option_ref) { print "$key, $val\n"; Returns a reference to a hash containing as keys all possible options for connectdb(). The values are the current defaults. This function differs from his C-counterpart, which returns the complete conninfoOption structure. PQfinish($conn) Old style only ! Closes the connection to the backend and frees the connection data structure. $conn->reset Resets the communication port with the backend and tries to establish a new connection. $ret = $conn->requestCancel Abandon processing of the current query. Regardless of the return value of requestCancel, the application must continue with the normal result-reading sequence using getResult. If the current query is part of a transaction, cancellation will abort the whole transaction. $dbname = $conn->db Returns the database name of the connection. $pguser = $conn->user Returns the Postgres user name of the connection. $pguser = $conn->pass Returns the Postgres password of the connection. $pghost = $conn->host Returns the host name of the connection. $pgport = $conn->port Returns the port of the connection. $pgtty = $conn->tty Returns the tty of the connection. $pgoptions = $conn->options Returns the options used in the connection. $status = $conn->status Returns the status of the connection. For comparing the status you may use the following constants: - PGRES_CONNECTION_OK - PGRES_CONNECTION_BAD $errorMessage = $conn->errorMessage Returns the last error message associated with this connection. $fd = $conn->socket Obtain the file descriptor number for the backend connection socket. A result of -1 indicates that no backend connection is currently open. $pid = $conn->backendPID Returns the process-id of the corresponding backend proceess. $conn->trace(debug_port) Messages passed between frontend and backend are echoed to the debug_port file stream. $conn->untrace Disables tracing. $result = $conn->exec($query) Submits a query to the backend. The return value is a pointer to the PGresult structure, which contains the complete query-result returned by the backend. In case of failure, the pointer points to an empty structure. In this, the perl implementation differs from the C-implementation. Using the old style, even the empty structure has to be freed using PQfree. Before using $result you should call resultStatus to ensure, that the query was properly executed. ($table, $pid) = $conn->notifies Checks for asynchronous notifications. This functions differs from the C-counterpart which returns a pointer to a new allocated structure, whereas the perl implementation returns a list. $table is the table which has been listened to and $pid is the process id of the backend. $ret = $conn->sendQuery($string, $query) Submit a query to Postgres without waiting for the result(s). After successfully calling PQsendQuery, call PQgetResult one or more times to obtain the query results. PQsendQuery may not be called again until getResult has returned NULL, indicating that the query is done. $result = $conn->getResult Wait for the next result from a prior PQsendQuery, and return it. NULL is returned when the query is complete and there will be no more results. getResult will block only if a query is active and the necessary response data has not yet been read by PQconsumeInput. $ret = $conn->isBusy Returns TRUE if a query is busy, that is, PQgetResult would block waiting for input. A FALSE return indicates that PQgetResult can be called with assurance of not blocking. $result = $conn->consumeInput If input is available from the backend, consume it. After calling consumeInput, the application may check isBusy and/or notifies to see if their state has changed. $ret = $conn->getline($string, $length) Reads a string up to $length - 1 characters from the backend. getline returns EOF at EOF, 0 if the entire line has been read, and 1 if the buffer is full. If a line consists of the two characters "\." the backend has finished sending the results of the copy command. $ret = $conn->putline($string) Sends a string to the backend. The application must explicitly send the two characters "\." to indicate to the backend that it has finished sending its data. $ret = $conn->getlineAsync($buffer, $bufsize) Non-blocking version of getline. It reads up to $bufsize characters from the backend. getlineAsync returns -1 if the end-of-copy-marker has been recognized, 0 if no data is avilable, and >0 the number of bytes returned. $ret = $conn->putnbytes($buffer, $nbytes) Sends n bytes to the backend. Returns 0 if OK, EOF if not. $ret = $conn->endcopy This function waits until the backend has finished the copy. It should either be issued when the last string has been sent to the backend using putline or when the last string has been received from the backend using getline. endcopy returns 0 on success, 1 on failure. $result = $conn->makeEmptyPGresult($status); Returns a newly allocated, initialized result with given status. =head2 2. Result With these functions you can send commands to a database and investigate the results. In Libpq the result of a command is represented by a structure called PGresult. Using the appropriate methods you can access almost all fields of this structure. $result_status = $result->resultStatus Returns the status of the result. For comparing the status you may use one of the following constants depending upon the command executed: - PGRES_EMPTY_QUERY - PGRES_COMMAND_OK - PGRES_TUPLES_OK - PGRES_COPY_OUT - PGRES_COPY_IN - PGRES_BAD_RESPONSE - PGRES_NONFATAL_ERROR - PGRES_FATAL_ERROR Use the functions below to access the contents of the PGresult structure. $ntuples = $result->ntuples Returns the number of tuples in the query result. $nfields = $result->nfields Returns the number of fields in the query result. $ret = $result->binaryTuples Returns 1 if the tuples in the query result are bianry. $fname = $result->fname($field_num) Returns the field name associated with the given field number. $fnumber = $result->fnumber($field_name) Returns the field number associated with the given field name. $ftype = $result->ftype($field_num) Returns the oid of the type of the given field number. $fsize = $result->fsize($field_num) Returns the size in bytes of the type of the given field number. It returns -1 if the field has a variable length. $fmod = $result->fmod($field_num) Returns the type-specific modification data of the field associated with the given field index. Field indices start at 0. $cmdStatus = $result->cmdStatus Returns the command status of the last query command. In case of DELETE it returns also the number of deleted tuples. In case of INSERT it returns also the OID of the inserted tuple followed by 1 (the number of affected tuples). $oid = $result->oidStatus In case the last query was an INSERT command it returns the oid of the inserted tuple. $oid = $result->cmdTuples In case the last query was an INSERT or DELETE command it returns the number of affected tuples. $value = $result->getvalue($tup_num, $field_num) Returns the value of the given tuple and field. This is a null-terminated ASCII string. Binary cursors will not work. $length = $result->getlength($tup_num, $field_num) Returns the length of the value for a given tuple and field. $null_status = $result->getisnull($tup_num, $field_num) Returns the NULL status for a given tuple and field. PQclear($result) Old style only ! Frees all memory of the given result. $res->fetchrow New style only ! Fetches the next row from the server and returns NULL if all rows have been processed. Columns which have NULL as value will be set to C. $result->print($fout, $header, $align, $standard, $html3, $expanded, $pager, $fieldSep, $tableOpt, $caption, ...) Prints out all the tuples in an intelligent manner. This function differs from the C-counterpart. The struct PQprintOpt has been implemented with a list. This list is of variable length, in order to care for the character array fieldName in PQprintOpt. The arguments $header, $align, $standard, $html3, $expanded, $pager are boolean flags. The arguments $fieldSep, $tableOpt, $caption are strings. You may append additional strings, which will be taken as replacement for the field names. $result->displayTuples($fp, $fillAlign, $fieldSep, $printHeader, qiet) Kept for backward compatibility. Use print. $result->printTuples($fout, $printAttName, $terseOutput, $width) Kept for backward compatibility. Use print. =head2 3. Large Objects These functions provide file-oriented access to user data. The large object interface is modeled after the Unix file system interface with analogies of open, close, read, write, lseek, tell. In order to get a consistent naming, all function names have been prepended with 'PQ' (old style only). $lobj_fd = $conn->lo_open($lobjId, $mode) Opens an existing large object and returns an object id. For the mode bits see lo_create. Returns -1 upon failure. $ret = $conn->lo_close($lobj_fd) Closes an existing large object. Returns 0 upon success and -1 upon failure. $nbytes = $conn->lo_read($lobj_fd, $buf, $len) Reads $len bytes into $buf from large object $lobj_fd. Returns the number of bytes read and -1 upon failure. $nbytes = $conn->lo_write($lobj_fd, $buf, $len) Writes $len bytes of $buf into the large object $lobj_fd. Returns the number of bytes written and -1 upon failure. $ret = $conn->lo_lseek($lobj_fd, $offset, $whence) Change the current read or write location on the large object $obj_id. Currently $whence can only be 0 (L_SET). $lobjId = $conn->lo_creat($mode) Creates a new large object. $mode is a bit-mask describing different attributes of the new object. Use the following constants: - PGRES_INV_SMGRMASK - PGRES_INV_ARCHIVE - PGRES_INV_WRITE - PGRES_INV_READ Upon failure it returns PGRES_InvalidOid. $location = $conn->lo_tell($lobj_fd) Returns the current read or write location on the large object $lobj_fd. $ret = $conn->lo_unlink($lobjId) Deletes a large object. Returns -1 upon failure. $lobjId = $conn->lo_import($filename) Imports a Unix file as large object and returns the object id of the new object. $ret = $conn->lo_export($lobjId, $filename) Exports a large object into a Unix file. Returns -1 upon failure, 1 otherwise. =head1 AUTHOR Edmund Mergl =head1 SEE ALSO L, L =cut