| 1 |
=head1 NAME |
| 2 |
|
| 3 |
PApp::SQL - absolutely easy yet fast and powerful sql access |
| 4 |
|
| 5 |
=head1 SYNOPSIS |
| 6 |
|
| 7 |
use PApp::SQL; |
| 8 |
# to be written |
| 9 |
|
| 10 |
=head1 DESCRIPTION |
| 11 |
|
| 12 |
This module provides you with easy-to-use functions to execute sql |
| 13 |
commands (using DBI). Despite being easy to use, they are also quite |
| 14 |
efficient and allow you to write faster programs in less lines of code. |
| 15 |
|
| 16 |
=over 4 |
| 17 |
|
| 18 |
=cut |
| 19 |
|
| 20 |
package PApp::SQL; |
| 21 |
|
| 22 |
use DBI; |
| 23 |
|
| 24 |
#use PApp::Exception; # not yet used |
| 25 |
|
| 26 |
BEGIN { |
| 27 |
use base Exporter; |
| 28 |
|
| 29 |
$VERSION = 0.11; |
| 30 |
@EXPORT = qw( |
| 31 |
sql_exec sql_fetch sql_fetchall sql_exists sql_insertid $sql_exec |
| 32 |
); |
| 33 |
@EXPORT_OK = qw( |
| 34 |
connect_cached |
| 35 |
); |
| 36 |
|
| 37 |
require XSLoader; |
| 38 |
XSLoader::load PApp::SQL, $VERSION; |
| 39 |
} |
| 40 |
|
| 41 |
our $sql_exec; # last result of sql_exec's execute call |
| 42 |
our $DBH; # the default database handle |
| 43 |
our $database; # the current SQL::Database object, if applicable |
| 44 |
|
| 45 |
our %dbcache; |
| 46 |
|
| 47 |
=item $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect |
| 48 |
|
| 49 |
(not exported by by default) |
| 50 |
|
| 51 |
Connect to the database given by C<($dsn,$user,$pass)>, while using the |
| 52 |
flags from C<$flags>. These are just the same arguments as given to |
| 53 |
C<DBI->connect>. |
| 54 |
|
| 55 |
The database handle will be cached under the unique id |
| 56 |
C<$id|$dsn|$user|$pass>. If the same id is requested later, the |
| 57 |
cached handle will be checked (using ping), and the connection will |
| 58 |
be re-established if necessary (be sure to prefix your application or |
| 59 |
module name to the id to make it "more" unique. Things like __PACKAGE__ . |
| 60 |
__LINE__ work fine as well). |
| 61 |
|
| 62 |
The reason C<$id> is necessary is that you might specify special connect |
| 63 |
arguments or special flags, or you might want to configure your $DBH |
| 64 |
differently than maybe other applications requesting the same database |
| 65 |
connection. If none of this is becessary for your application you can |
| 66 |
leave $id empty (i.e. ""). |
| 67 |
|
| 68 |
If specified, C<$connect> is a callback (e.g. a coderef) that will be |
| 69 |
called each time a new connection is being established, with the new |
| 70 |
C<$dbh> as first argument. |
| 71 |
|
| 72 |
Examples: |
| 73 |
|
| 74 |
# try your luck opening the papp database without access info |
| 75 |
$dbh = connect_cached __FILE__, "DBI:mysql:papp"; |
| 76 |
|
| 77 |
=cut |
| 78 |
|
| 79 |
sub connect_cached { |
| 80 |
my ($id, $dsn, $user, $pass, $flags, $connect) = @_; |
| 81 |
# the following line is duplicated in PApp::SQL::Database::new |
| 82 |
$id = "$id\0$dsn\0$user\0$pass"; |
| 83 |
unless ($dbcache{$id} && $dbcache{$id}->ping) { |
| 84 |
#warn "connecting to ($dsn|$user|$pass|$flags)\n";#d# |
| 85 |
# first, nuke our statement cache (sooory ;) |
| 86 |
cachesize cachesize 0; |
| 87 |
# then connect anew |
| 88 |
$dbcache{$id} = |
| 89 |
eval { DBI->connect($dsn, $user, $pass, $flags) } |
| 90 |
|| eval { DBI->connect($dsn, $user, $pass, $flags) } |
| 91 |
|| die "unable to connect to database $dsn: $DBI::errstr\n"; |
| 92 |
$connect->($dbcache{$id}) if $connect; |
| 93 |
} |
| 94 |
$dbcache{$id}; |
| 95 |
} |
| 96 |
|
| 97 |
=item $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...] |
| 98 |
|
| 99 |
C<sql_exec> is the most important and most-used function in this module. |
| 100 |
|
| 101 |
Runs the given sql command with the given parameters and returns the |
| 102 |
statement handle. The command and the statement handle will be cached |
| 103 |
(with the database handle and the sql string as key), so prepare will be |
| 104 |
called only once for each distinct sql call (please keep in mind that the |
| 105 |
returned statement will always be the same, so, if you call C<sql_exec> |
| 106 |
with the same dbh and sql-statement twice (e.g. in a subroutine you |
| 107 |
called), the statement handle for the first call mustn't be used. |
| 108 |
|
| 109 |
The database handle (the first argument) is optional. If it is missing, |
| 110 |
C<sql_exec> first tries to use the variable C<$DBH> in the current (= |
| 111 |
calling) package and, if that fails, it tries to use database handle in |
| 112 |
C<$PApp::SQL::DBH>, which you can set before calling these functions. |
| 113 |
|
| 114 |
The actual return value from the C<$sth->execute> call is stored in the |
| 115 |
package-global (and exported) variable C<$sql_exec>. |
| 116 |
|
| 117 |
If any error occurs C<sql_exec> will throw an exception. |
| 118 |
|
| 119 |
Examples: |
| 120 |
|
| 121 |
# easy one |
| 122 |
my $st = sql_exec "select name, id from table where id = ?", $id; |
| 123 |
while (my ($name, $id) = $st->fetchrow_array) { ... }; |
| 124 |
|
| 125 |
# the fastest way to use dbi, using bind_columns |
| 126 |
my $st = sql_exec \my($name, $id), |
| 127 |
"select name, id from table where id = ?", |
| 128 |
$id; |
| 129 |
while ($st->fetch) { ...} |
| 130 |
|
| 131 |
# now use a different dastabase: |
| 132 |
sql_exec $dbh, "update file set name = ?", "oops.txt"; |
| 133 |
|
| 134 |
|
| 135 |
=item sql_fetch <see sql_exec> |
| 136 |
|
| 137 |
Execute a sql-statement and fetch the first row of results. Depending on |
| 138 |
the caller context the row will be returned as a list (array context), or |
| 139 |
just the first columns. In table form: |
| 140 |
|
| 141 |
CONTEXT RESULT |
| 142 |
void () |
| 143 |
scalar first column |
| 144 |
list array |
| 145 |
|
| 146 |
C<sql_fetch> is quite efficient in conjunction with bind variables: |
| 147 |
|
| 148 |
sql_fetch \my($name, $amount), |
| 149 |
"select name, amount from table where id name = ?", |
| 150 |
"Toytest"; |
| 151 |
|
| 152 |
But of course the normal way to call it is simply: |
| 153 |
|
| 154 |
my($name, $amount) = sql_fetch "select ...", args... |
| 155 |
|
| 156 |
... and it's still quite fast unless you fetch large amounts of data. |
| 157 |
|
| 158 |
=item sql_fetchall <see sql_exec> |
| 159 |
|
| 160 |
Similarly to C<sql_fetch>, but all result rows will be fetched (this is |
| 161 |
of course inefficient for large results!). The context is ignored (only |
| 162 |
list context makes sense), but the result still depends on the number of |
| 163 |
columns in the result: |
| 164 |
|
| 165 |
COLUMNS RESULT |
| 166 |
0 () |
| 167 |
1 (row1, row2, row3...) |
| 168 |
many ([row1], [row2], [row3]...) |
| 169 |
|
| 170 |
Examples (all of which are inefficient): |
| 171 |
|
| 172 |
for (sql_fetchall "select id from table") { ... } |
| 173 |
|
| 174 |
my @names = sql_fetchall "select name from user"; |
| 175 |
|
| 176 |
for (sql_fetchall "select name, age, place from user") { |
| 177 |
my ($name, $age, $place) = @$_; |
| 178 |
} |
| 179 |
|
| 180 |
=item sql_exists "<table> where ...", args... |
| 181 |
|
| 182 |
Check wether the result of the sql-statement "select xxx from |
| 183 |
$first_argument" would be empty or not (that is, imagine the string |
| 184 |
"select from" were prepended to your statement (it isn't)). Should work |
| 185 |
with every database but can be quite slow, except on mysql, where this |
| 186 |
should be quite fast. |
| 187 |
|
| 188 |
Examples: |
| 189 |
|
| 190 |
print "user 7 exists!\n" |
| 191 |
if sql_exists "user where id = ?", 7; |
| 192 |
|
| 193 |
die "duplicate key" |
| 194 |
if sql_exists "user where name = ? and pass = ?", "stefan", "geheim"; |
| 195 |
|
| 196 |
=cut |
| 197 |
|
| 198 |
=item $lastid = sql_insertid $sth |
| 199 |
|
| 200 |
Returns the last automatically created key value. It must be executed |
| 201 |
directly after executing the insert statement that created it. This is |
| 202 |
what is actually returned for various databases. If your database is |
| 203 |
missing, please send me an e-mail on how to implement this ;) |
| 204 |
|
| 205 |
mysql: first C<AUTO_INCREMENT> column set to NULL |
| 206 |
postgres: C<oid> column (is there a way to get the last SERIAL?) |
| 207 |
sybase: C<IDENTITY> column of the last insert (slow) |
| 208 |
informix: C<SERIAL> or C<SERIAL8> column of the last insert |
| 209 |
|
| 210 |
Except for sybase, this does not require a server access. |
| 211 |
|
| 212 |
=cut |
| 213 |
|
| 214 |
sub sql_insertid($) { |
| 215 |
my $sth = shift or die "sql_insertid requires a statement handle"; |
| 216 |
my $dbh = $sth->{Database}; |
| 217 |
my $driver = $dbh->{Driver}{Name}; |
| 218 |
|
| 219 |
$driver eq "mysql" and return $sth->{mysql_insertid}; |
| 220 |
$driver eq "Pg" and return $sth->{pg_oid_status}; |
| 221 |
$driver eq "Sybase" and return sql_fetch($dbh, 'SELECT @@IDENTITY'); |
| 222 |
$driver eq "Informix" and return $sth->{ix_sqlerrd}[1]; |
| 223 |
|
| 224 |
die "sql_insertid does not spport the dbd driver '$driver', please see PApp::SQL::sql_insertid"; |
| 225 |
} |
| 226 |
|
| 227 |
=item [old-size] = cachesize [new-size] |
| 228 |
|
| 229 |
Returns (and possibly changes) the LRU cache size used by C<sql_exec>. The |
| 230 |
default is somewhere around 50 (= the 50 last recently used statements |
| 231 |
will be cached). It shouldn't be too large, since a simple linear listed |
| 232 |
is used for the cache at the moment (which, for small (<100) cache sizes |
| 233 |
is actually quite fast). |
| 234 |
|
| 235 |
The function always returns the cache size in effect I<before> the call, |
| 236 |
so, to nuke the cache (for example, when a database connection has died |
| 237 |
or you want to garbage collect old database/statement handles), this |
| 238 |
construct can be used: |
| 239 |
|
| 240 |
PApp::SQL::cachesize PApp::SQL::cachesize 0; |
| 241 |
|
| 242 |
=cut |
| 243 |
|
| 244 |
=item reinitialize [not exported] |
| 245 |
|
| 246 |
Clears any internal caches (statement cache, database handle |
| 247 |
cache). Should be called after C<fork> and other accidents that invalidate |
| 248 |
database handles. |
| 249 |
|
| 250 |
=cut |
| 251 |
|
| 252 |
sub reinitialize { |
| 253 |
cachesize cachesize 0; |
| 254 |
for (values %dbcache) { |
| 255 |
eval { $_->disconnect }; |
| 256 |
} |
| 257 |
undef %dbcache; |
| 258 |
} |
| 259 |
|
| 260 |
=back |
| 261 |
|
| 262 |
=cut |
| 263 |
|
| 264 |
reinitialize; |
| 265 |
|
| 266 |
package PApp::SQL::Database; |
| 267 |
|
| 268 |
=head2 THE DATABASE CLASS |
| 269 |
|
| 270 |
Again (sigh) the problem of persistency. What do you do when you have to serialize on object |
| 271 |
that contains (or should contain) a database handle? Short answer: you don't. Long answer: |
| 272 |
you can embed the necessary information to recreate the dbh when needed. |
| 273 |
|
| 274 |
The C<PApp::SQL::Database> class does that, in a relatively efficient |
| 275 |
fashion: the overhead is currently a single method call per access (you |
| 276 |
can cache the real dbh if you want). |
| 277 |
|
| 278 |
=over 4 |
| 279 |
|
| 280 |
=item $db = new <same arguments as C<connect_cached>> |
| 281 |
|
| 282 |
The C<new> call takes the same arguments as C<connect_cached> (obviously, |
| 283 |
if you supply a connect callback it better is serializable, see |
| 284 |
L<PApp::Callback>!) and returns a serializable database class. No database |
| 285 |
handle is actually being created. |
| 286 |
|
| 287 |
=item $db->dbh |
| 288 |
|
| 289 |
Return the database handle as fast as possible (usually just a hash lookup). |
| 290 |
|
| 291 |
=item $db->checked_dbh |
| 292 |
|
| 293 |
Return the database handle, but first check that the database is still |
| 294 |
available and re-open the connection if necessary. |
| 295 |
|
| 296 |
=cut |
| 297 |
|
| 298 |
sub new($$;@) { |
| 299 |
my $class = shift; |
| 300 |
my ($id, $dsn, $user, $pass, $flags, $connect) = @_; |
| 301 |
# the following line is duplicated in PApp::SQL::Database::new |
| 302 |
my $id2 = "$id\0$dsn\0$user\0$pass"; |
| 303 |
bless [$id2, $flags, $connect], $class; |
| 304 |
} |
| 305 |
|
| 306 |
# the following two functions better be fast! |
| 307 |
sub dbh($) { |
| 308 |
$dbcache{$_[0][0]} || $_[0]->checked_dbh; |
| 309 |
} |
| 310 |
|
| 311 |
sub checked_dbh($) { |
| 312 |
my $dbh = $dbcache{$_[0][0]}; |
| 313 |
$dbh && $dbh->ping |
| 314 |
? $dbh |
| 315 |
: PApp::SQL::connect_cached((split /\x00/, $_[0][0]), $_[0][1], $_[0][2]); |
| 316 |
} |
| 317 |
|
| 318 |
=item $db->dsn |
| 319 |
|
| 320 |
Return the DSN (L<DBI>) fo the database object (e.g. for error messages). |
| 321 |
|
| 322 |
=cut |
| 323 |
|
| 324 |
sub dsn($) { |
| 325 |
my $self = shift; |
| 326 |
(split /\x00/, $self->[0])[1]; |
| 327 |
} |
| 328 |
|
| 329 |
=back |
| 330 |
|
| 331 |
=cut |
| 332 |
|
| 333 |
1; |
| 334 |
|
| 335 |
=head1 BUGS |
| 336 |
|
| 337 |
As of this writing, sql_fetch and sql_fetchall are not very well tested |
| 338 |
(they were just re-written in C). |
| 339 |
|
| 340 |
sql_exists could be faster (it is written very ugly to not change the |
| 341 |
current package). |
| 342 |
|
| 343 |
=head1 SEE ALSO |
| 344 |
|
| 345 |
L<PApp>. |
| 346 |
|
| 347 |
=head1 AUTHOR |
| 348 |
|
| 349 |
Marc Lehmann <pcg@goof.com> |
| 350 |
http://www.goof.com/pcg/marc/ |
| 351 |
|
| 352 |
=cut |
| 353 |
|
