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3 | BDB - Asynchronous Berkeley DB access |
3 | BDB - Asynchronous Berkeley DB access |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use BDB; |
7 | use BDB; |
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8 | |
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9 | my $env = db_env_create; |
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10 | |
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11 | mkdir "bdtest", 0700; |
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12 | db_env_open |
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13 | $env, |
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14 | "bdtest", |
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15 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL |
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16 | | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
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17 | 0600; |
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18 | |
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19 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
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20 | |
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21 | my $db = db_create $env; |
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22 | db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE |
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23 | | BDB::READ_UNCOMMITTED, 0600; |
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24 | db_put $db, undef, "key", "data", 0, sub { |
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25 | db_del $db, undef, "key"; |
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26 | }; |
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27 | db_sync $db; |
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28 | |
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29 | # when you also use Coro, management is easy: |
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30 | use Coro::BDB; |
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31 | |
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32 | # automatic event loop intergration with AnyEvent: |
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33 | use AnyEvent::BDB; |
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34 | |
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35 | # automatic result processing with EV: |
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36 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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37 | |
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38 | # with Glib: |
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39 | add_watch Glib::IO BDB::poll_fileno, |
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40 | in => sub { BDB::poll_cb; 1 }; |
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41 | |
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42 | # or simply flush manually |
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43 | BDB::flush; |
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44 | |
8 | |
45 | |
9 | =head1 DESCRIPTION |
46 | =head1 DESCRIPTION |
10 | |
47 | |
11 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
48 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
12 | The BDB API is very similar to the C API (the translation has been very faithful). |
49 | The BDB API is very similar to the C API (the translation has been very faithful). |
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72 | use strict 'vars'; |
109 | use strict 'vars'; |
73 | |
110 | |
74 | use base 'Exporter'; |
111 | use base 'Exporter'; |
75 | |
112 | |
76 | BEGIN { |
113 | BEGIN { |
77 | our $VERSION = '1.1'; |
114 | our $VERSION = '1.6'; |
78 | |
115 | |
79 | our @BDB_REQ = qw( |
116 | our @BDB_REQ = qw( |
80 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
117 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
81 | db_env_memp_sync db_env_memp_trickle |
118 | db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove |
82 | db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range |
119 | db_open db_close db_compact db_sync db_upgrade |
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120 | db_put db_get db_pget db_del db_key_range |
83 | db_txn_commit db_txn_abort db_txn_finish |
121 | db_txn_commit db_txn_abort db_txn_finish |
84 | db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del |
122 | db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del |
85 | db_sequence_open db_sequence_close |
123 | db_sequence_open db_sequence_close |
86 | db_sequence_get db_sequence_remove |
124 | db_sequence_get db_sequence_remove |
87 | ); |
125 | ); |
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95 | |
133 | |
96 | require XSLoader; |
134 | require XSLoader; |
97 | XSLoader::load ("BDB", $VERSION); |
135 | XSLoader::load ("BDB", $VERSION); |
98 | } |
136 | } |
99 | |
137 | |
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138 | =head2 WIN32 FILENAMES/DATABASE NAME MESS |
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139 | |
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140 | Perl on Win32 supports only ASCII filenames (the reason is that it abuses |
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141 | an internal flag to store wether a filename is Unicode or ANSI, but that |
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142 | flag is used for somethign else in the perl core, so there is no way to |
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143 | detect wether a filename is ANSI or Unicode-encoded). The BDB module |
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144 | tries to work around this issue by assuming that the filename is an ANSI |
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145 | filename and BDB was built for unicode support. |
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146 | |
100 | =head2 BERKELEYDB FUNCTIONS |
147 | =head2 BERKELEYDB FUNCTIONS |
101 | |
148 | |
102 | All of these are functions. The create functions simply return a new |
149 | All of these are functions. The create functions simply return a new |
103 | object and never block. All the remaining functions all take an optional |
150 | object and never block. All the remaining functions take an optional |
104 | callback as last argument. If it is missing, then the fucntion will be |
151 | callback as last argument. If it is missing, then the function will be |
105 | executed synchronously. |
152 | executed synchronously. In both cases, C<$!> will reflect the return value |
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153 | of the function. |
106 | |
154 | |
107 | BDB functions that cannot block (mostly functions that manipulate |
155 | BDB functions that cannot block (mostly functions that manipulate |
108 | settings) are method calls on the relevant objects, so the rule of thumb |
156 | settings) are method calls on the relevant objects, so the rule of thumb |
109 | is: if its a method, its not blocking, if its a function, it takes a |
157 | is: if it's a method, it's not blocking, if it's a function, it takes a |
110 | callback as last argument. |
158 | callback as last argument. |
111 | |
159 | |
112 | In the following, C<$int> signifies an integer return value, |
160 | In the following, C<$int> signifies an integer return value, |
113 | C<octetstring> is a "binary string" (i.e. a perl string with no character |
161 | C<bdb_filename> is a "filename" (octets on unix, madness on windows), |
114 | indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some |
162 | C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a |
115 | integer, C<NV> is a floating point value. |
163 | floating point value. |
116 | |
164 | |
117 | The C<SV *> types are generic perl scalars (for input and output of data |
165 | Most C<SV *> types are generic perl scalars (for input and output of data |
118 | values), and the C<SV *callback> is the optional callback function to call |
166 | values). |
119 | when the request is completed. |
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120 | |
167 | |
121 | The various C<DB_ENV> etc. arguments are handles return by |
168 | The various C<DB_ENV> etc. arguments are handles return by |
122 | C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an |
169 | C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an |
123 | appended C<_ornull> this means they are optional and you can pass C<undef> |
170 | appended C<_ornull> this means they are optional and you can pass C<undef> |
124 | for them, resulting a NULL pointer on the C level. |
171 | for them, resulting a NULL pointer on the C level. |
125 | |
172 | |
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173 | The C<SV *callback> is the optional callback function to call when the |
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174 | request is completed. This last callback argument is special: the callback |
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175 | is simply the last argument passed. If there are "optional" arguments |
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176 | before the callback they can be left out. The callback itself can be left |
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177 | out or specified as C<undef>, in which case the function will be executed |
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178 | synchronously. |
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179 | |
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180 | For example, C<db_env_txn_checkpoint> usually is called with all integer |
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181 | arguments zero. These can be left out, so all of these specify a call |
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182 | to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a |
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183 | callback to be called: |
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184 | |
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185 | db_env_txn_checkpoint $db_env, 0, 0, 0, sub { }; |
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186 | db_env_txn_checkpoint $db_env, 0, 0, sub { }; |
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187 | db_env_txn_checkpoint $db_env, sub { }; |
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188 | |
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189 | While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be |
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190 | executed synchronously: |
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191 | |
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192 | db_env_txn_checkpoint $db_env, 0, 0, 0, undef; |
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193 | db_env_txn_checkpoint $db_env, 0, 0, 0; |
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194 | db_env_txn_checkpoint $db_env, 0; |
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195 | |
126 | =head3 BDB functions |
196 | =head3 BDB functions |
127 | |
197 | |
128 | Functions in the BDB namespace, exported by default: |
198 | Functions in the BDB namespace, exported by default: |
129 | |
199 | |
130 | $env = db_env_create (U32 env_flags = 0) |
200 | $env = db_env_create (U32 env_flags = 0) |
131 | flags: RPCCLIENT |
201 | flags: RPCCLIENT |
132 | |
202 | |
133 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
203 | db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
134 | open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM |
204 | open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM |
135 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
205 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
136 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
206 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
137 | flags: FORCE |
207 | flags: FORCE |
138 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
208 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
139 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
209 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
140 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
210 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
141 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
211 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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212 | db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef) |
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213 | db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef) |
142 | |
214 | |
143 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
215 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
144 | flags: XA_CREATE |
216 | flags: XA_CREATE |
145 | |
217 | |
146 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
218 | db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
147 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
219 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
148 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
220 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
149 | flags: DB_NOSYNC |
221 | flags: DB_NOSYNC |
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222 | db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef) |
150 | db_compact (DB *db, DB_TXN_ornull *txn = 0, SV *start = 0, SV *stop = 0, SV *unused1 = 0, U32 flags = DB_FREE_SPACE, SV *unused2 = 0, SV *callback = &PL_sv_undef) |
223 | db_compact (DB *db, DB_TXN_ornull *txn = 0, SV *start = 0, SV *stop = 0, SV *unused1 = 0, U32 flags = DB_FREE_SPACE, SV *unused2 = 0, SV *callback = &PL_sv_undef) |
151 | flags: FREELIST_ONLY FREE_SPACE |
224 | flags: FREELIST_ONLY FREE_SPACE |
152 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
225 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
153 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
226 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
154 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
227 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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179 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
252 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
180 | flags: TXN_NOSYNC |
253 | flags: TXN_NOSYNC |
181 | |
254 | |
182 | =head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
255 | =head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
183 | |
256 | |
184 | This is not a Berkeley DB function but a BDB module extension. It is very |
257 | This is not actually a Berkeley DB function but a BDB module |
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258 | extension. The background for this exytension is: It is very annoying to |
185 | annoying to have to check every single BDB function for error returns and |
259 | have to check every single BDB function for error returns and provide a |
186 | provide a codepath out of your transaction. While the BDB module still |
260 | codepath out of your transaction. While the BDB module still makes this |
187 | makes this possible, it contains the following extensions: |
261 | possible, it contains the following extensions: |
188 | |
262 | |
189 | When a transaction-protected function returns any operating system |
263 | When a transaction-protected function returns any operating system |
190 | error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the |
264 | error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the |
191 | transaction. This flag is also set by Berkeley DB functions externally |
265 | transaction. This flag is also set by Berkeley DB functions themselves |
192 | when an operation fails with LOCK_DEADLOCK, and it causes all further |
266 | when an operation fails with LOCK_DEADLOCK, and it causes all further |
193 | operations on that transaction (including C<db_txn_commit>) to fail. |
267 | operations on that transaction (including C<db_txn_commit>) to fail. |
194 | |
268 | |
195 | The C<db_txn_finish> request will look at this flag, and, if it is set, |
269 | The C<db_txn_finish> request will look at this flag, and, if it is set, |
196 | will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> |
270 | will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> |
197 | if it isn't set). If it isn't set, it will call C<db_txn_commit> and |
271 | if it isn't set to something else yet). If it isn't set, it will call |
198 | return the error normally. |
272 | C<db_txn_commit> and return the error normally. |
199 | |
273 | |
200 | How to use this? Easy: just write your transaction normally: |
274 | How to use this? Easy: just write your transaction normally: |
201 | |
275 | |
202 | my $txn = $db_env->txn_begin; |
276 | my $txn = $db_env->txn_begin; |
203 | db_get $db, $txn, "key", my $data; |
277 | db_get $db, $txn, "key", my $data; |
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208 | That is, handle only the expected errors. If something unexpected happens |
282 | That is, handle only the expected errors. If something unexpected happens |
209 | (EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining |
283 | (EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining |
210 | requests (db_put in this case) will simply be skipped (they will fail with |
284 | requests (db_put in this case) will simply be skipped (they will fail with |
211 | LOCK_DEADLOCK) and the transaction will be aborted. |
285 | LOCK_DEADLOCK) and the transaction will be aborted. |
212 | |
286 | |
213 | You cna use the C<< $txn->failed >> method to check wether a transaction |
287 | You can use the C<< $txn->failed >> method to check wether a transaction |
214 | has failed in this way and abort further processing (excluding |
288 | has failed in this way and abort further processing (excluding |
215 | C<db_txn_finish>). |
289 | C<db_txn_finish>). |
216 | |
290 | |
217 | =head3 DB_ENV/database environment methods |
291 | =head3 DB_ENV/database environment methods |
218 | |
292 | |
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226 | $int = $env->set_data_dir (const char *dir) |
300 | $int = $env->set_data_dir (const char *dir) |
227 | $int = $env->set_tmp_dir (const char *dir) |
301 | $int = $env->set_tmp_dir (const char *dir) |
228 | $int = $env->set_lg_dir (const char *dir) |
302 | $int = $env->set_lg_dir (const char *dir) |
229 | $int = $env->set_shm_key (long shm_key) |
303 | $int = $env->set_shm_key (long shm_key) |
230 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
304 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
231 | $int = $env->set_flags (U32 flags, int onoff) |
305 | $int = $env->set_flags (U32 flags, int onoff = 1) |
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306 | $int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7] |
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307 | $int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7] |
232 | $env->set_errfile (FILE *errfile = 0) |
308 | $env->set_errfile (FILE *errfile = 0) |
233 | $env->set_msgfile (FILE *msgfile = 0) |
309 | $env->set_msgfile (FILE *msgfile = 0) |
234 | $int = $env->set_verbose (U32 which, int onoff = 1) |
310 | $int = $env->set_verbose (U32 which, int onoff = 1) |
235 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
311 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
236 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
312 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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241 | $int = $env->set_lk_max_lockers (U32 max) |
317 | $int = $env->set_lk_max_lockers (U32 max) |
242 | $int = $env->set_lk_max_locks (U32 max) |
318 | $int = $env->set_lk_max_locks (U32 max) |
243 | $int = $env->set_lk_max_objects (U32 max) |
319 | $int = $env->set_lk_max_objects (U32 max) |
244 | $int = $env->set_lg_bsize (U32 max) |
320 | $int = $env->set_lg_bsize (U32 max) |
245 | $int = $env->set_lg_max (U32 max) |
321 | $int = $env->set_lg_max (U32 max) |
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322 | $int = $env->mutex_set_increment (U32 increment) |
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323 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
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324 | $int = $env->mutex_set_max (U32 max) |
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325 | $int = $env->mutex_set_align (U32 align) |
246 | |
326 | |
247 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
327 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
248 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
328 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
249 | |
329 | |
250 | =head4 Example: |
330 | =head4 Example: |
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345 | DESTROY (DBC_ornull *dbc) |
425 | DESTROY (DBC_ornull *dbc) |
346 | CODE: |
426 | CODE: |
347 | if (dbc) |
427 | if (dbc) |
348 | dbc->c_close (dbc); |
428 | dbc->c_close (dbc); |
349 | |
429 | |
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430 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
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431 | |
350 | =head4 Example: |
432 | =head4 Example: |
351 | |
433 | |
352 | my $c = $db->cursor; |
434 | my $c = $db->cursor; |
353 | |
435 | |
354 | for (;;) { |
436 | for (;;) { |
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387 | |
469 | |
388 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
470 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
389 | |
471 | |
390 | =over 4 |
472 | =over 4 |
391 | |
473 | |
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474 | =item $msg = BDB::strerror [$errno] |
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475 | |
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476 | Returns the string corresponding to the given errno value. If no argument |
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477 | is given, use C<$!>. |
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478 | |
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479 | Note that the BDB module also patches the C<$!> variable directly, so you |
|
|
480 | should be able to get a bdb error string by simply stringifying C<$!>. |
|
|
481 | |
392 | =item $fileno = BDB::poll_fileno |
482 | =item $fileno = BDB::poll_fileno |
393 | |
483 | |
394 | Return the I<request result pipe file descriptor>. This filehandle must be |
484 | Return the I<request result pipe file descriptor>. This filehandle must be |
395 | polled for reading by some mechanism outside this module (e.g. Event or |
485 | polled for reading by some mechanism outside this module (e.g. Event or |
396 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
486 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
… | |
… | |
434 | interactiveness when perl is not fast enough to process all requests in |
524 | interactiveness when perl is not fast enough to process all requests in |
435 | time. |
525 | time. |
436 | |
526 | |
437 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
527 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
438 | |
528 | |
439 | Example: Install an Event watcher that automatically calls |
529 | Example: Install an EV watcher that automatically calls |
440 | BDB::poll_cb with low priority, to ensure that other parts of the |
530 | BDB::poll_cb with low priority, to ensure that other parts of the |
441 | program get the CPU sometimes even under high AIO load. |
531 | program get the CPU sometimes even under high load. |
442 | |
532 | |
443 | # try not to spend much more than 0.1s in poll_cb |
533 | # try not to spend much more than 0.1s in poll_cb |
444 | BDB::max_poll_time 0.1; |
534 | BDB::max_poll_time 0.1; |
445 | |
535 | |
446 | # use a low priority so other tasks have priority |
536 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
447 | Event->io (fd => BDB::poll_fileno, |
|
|
448 | poll => 'r', nice => 1, |
|
|
449 | cb => &BDB::poll_cb); |
|
|
450 | |
537 | |
451 | =item BDB::poll_wait |
538 | =item BDB::poll_wait |
452 | |
539 | |
453 | If there are any outstanding requests and none of them in the result |
540 | If there are any outstanding requests and none of them in the result |
454 | phase, wait till the result filehandle becomes ready for reading (simply |
541 | phase, wait till the result filehandle becomes ready for reading (simply |
… | |
… | |
466 | |
553 | |
467 | BDB::poll_wait, BDB::poll_cb |
554 | BDB::poll_wait, BDB::poll_cb |
468 | |
555 | |
469 | =item BDB::flush |
556 | =item BDB::flush |
470 | |
557 | |
471 | Wait till all outstanding AIO requests have been handled. |
558 | Wait till all outstanding BDB requests have been handled. |
472 | |
559 | |
473 | Strictly equivalent to: |
560 | Strictly equivalent to: |
474 | |
561 | |
475 | BDB::poll_wait, BDB::poll_cb |
562 | BDB::poll_wait, BDB::poll_cb |
476 | while BDB::nreqs; |
563 | while BDB::nreqs; |
477 | |
564 | |
478 | =back |
565 | =back |
479 | |
566 | |
|
|
567 | =head3 VERSION CHECKING |
|
|
568 | |
|
|
569 | BerkeleyDB comes in various versions, many of them have minor |
|
|
570 | incompatibilities. This means that traditional "at least version x.x" |
|
|
571 | checks are often not sufficient. |
|
|
572 | |
|
|
573 | Example: set the log_autoremove option in a way compatible with <v.47 and |
|
|
574 | v4.7. Note the use of & on the constants to avoid triggering a compiletime |
|
|
575 | bug when the symbol isn't available. |
|
|
576 | |
|
|
577 | $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7; |
|
|
578 | $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7; |
|
|
579 | |
|
|
580 | =over 4 |
|
|
581 | |
|
|
582 | =item BDB::VERSION |
|
|
583 | |
|
|
584 | The C<BDB::VERSION> function, when called without arguments, returns the |
|
|
585 | Berkeley DB version as a v-string (usually with 3 components). You should |
|
|
586 | use C<lt> and C<ge> operators exclusively to make comparisons. |
|
|
587 | |
|
|
588 | Example: check for at least version 4.7. |
|
|
589 | |
|
|
590 | BDB::VERSION ge v4.7 or die; |
|
|
591 | |
|
|
592 | =item BDB::VERSION min-version |
|
|
593 | |
|
|
594 | Returns true if the BDB version is at least the given version (specified |
|
|
595 | as a v-string), false otherwise. |
|
|
596 | |
|
|
597 | Example: check for at least version 4.5. |
|
|
598 | |
|
|
599 | BDB::VERSION v4.7 or die; |
|
|
600 | |
|
|
601 | =item BDB::VERSION min-version, max-version |
|
|
602 | |
|
|
603 | Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version) |
|
|
604 | and less then C<max-version>. |
|
|
605 | |
|
|
606 | Example: check wether version is strictly less then v4.7. |
|
|
607 | |
|
|
608 | BDB::VERSION v0, v4.7 |
|
|
609 | or die "version 4.7 is not yet supported"; |
|
|
610 | |
|
|
611 | =back |
|
|
612 | |
|
|
613 | =cut |
|
|
614 | |
|
|
615 | sub VERSION { |
|
|
616 | if (@_ > 0) { |
|
|
617 | return undef if VERSION_v lt $_[0]; |
|
|
618 | if (@_ > 1) { |
|
|
619 | return undef if VERSION_v ge $_[1]; |
|
|
620 | } |
|
|
621 | } |
|
|
622 | |
|
|
623 | VERSION_v |
|
|
624 | } |
|
|
625 | |
480 | =head3 CONTROLLING THE NUMBER OF THREADS |
626 | =head3 CONTROLLING THE NUMBER OF THREADS |
481 | |
627 | |
482 | =over 4 |
628 | =over 4 |
483 | |
629 | |
484 | =item BDB::min_parallel $nthreads |
630 | =item BDB::min_parallel $nthreads |
485 | |
631 | |
486 | Set the minimum number of AIO threads to C<$nthreads>. The current |
632 | Set the minimum number of BDB threads to C<$nthreads>. The current |
487 | default is C<8>, which means eight asynchronous operations can execute |
633 | default is C<8>, which means eight asynchronous operations can execute |
488 | concurrently at any one time (the number of outstanding requests, |
634 | concurrently at any one time (the number of outstanding requests, |
489 | however, is unlimited). |
635 | however, is unlimited). |
490 | |
636 | |
491 | BDB starts threads only on demand, when an AIO request is queued and |
637 | BDB starts threads only on demand, when an BDB request is queued and |
492 | no free thread exists. Please note that queueing up a hundred requests can |
638 | no free thread exists. Please note that queueing up a hundred requests can |
493 | create demand for a hundred threads, even if it turns out that everything |
639 | create demand for a hundred threads, even if it turns out that everything |
494 | is in the cache and could have been processed faster by a single thread. |
640 | is in the cache and could have been processed faster by a single thread. |
495 | |
641 | |
496 | It is recommended to keep the number of threads relatively low, as some |
642 | It is recommended to keep the number of threads relatively low, as some |
… | |
… | |
501 | Under most circumstances you don't need to call this function, as the |
647 | Under most circumstances you don't need to call this function, as the |
502 | module selects a default that is suitable for low to moderate load. |
648 | module selects a default that is suitable for low to moderate load. |
503 | |
649 | |
504 | =item BDB::max_parallel $nthreads |
650 | =item BDB::max_parallel $nthreads |
505 | |
651 | |
506 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
652 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
507 | specified number of threads are currently running, this function kills |
653 | specified number of threads are currently running, this function kills |
508 | them. This function blocks until the limit is reached. |
654 | them. This function blocks until the limit is reached. |
509 | |
655 | |
510 | While C<$nthreads> are zero, aio requests get queued but not executed |
656 | While C<$nthreads> are zero, aio requests get queued but not executed |
511 | until the number of threads has been increased again. |
657 | until the number of threads has been increased again. |
… | |
… | |
550 | |
696 | |
551 | =item BDB::set_sync_prepare $cb |
697 | =item BDB::set_sync_prepare $cb |
552 | |
698 | |
553 | Sets a callback that is called whenever a request is created without an |
699 | Sets a callback that is called whenever a request is created without an |
554 | explicit callback. It has to return two code references. The first is used |
700 | explicit callback. It has to return two code references. The first is used |
555 | as the request callback, and the second is called to wait until the first |
701 | as the request callback (it should save the return status), and the second |
|
|
702 | is called to wait until the first callback has been called (it must set |
|
|
703 | C<$!> to the return status). |
|
|
704 | |
|
|
705 | This mechanism can be used to include BDB into other event mechanisms, |
|
|
706 | such as L<AnyEvent::BDB> or L<Coro::BDB>. |
|
|
707 | |
556 | callback has been called. The default implementation works like this: |
708 | The default implementation works like this: |
557 | |
709 | |
558 | sub { |
710 | sub { |
559 | my $status; |
711 | my $status; |
560 | ( |
712 | ( |
561 | sub { $status = $! }, |
713 | sub { $status = $! }, |
562 | sub { BDB::poll while !defined $status; $! = $status }, |
714 | sub { BDB::poll while !defined $status; $! = $status }, |
563 | ) |
715 | ) |
564 | } |
716 | } |
|
|
717 | |
|
|
718 | It simply blocks the process till the request has finished and then sets |
|
|
719 | C<$!> to the return value. This means that if you don't use a callback, |
|
|
720 | BDB will simply fall back to synchronous operations. |
565 | |
721 | |
566 | =back |
722 | =back |
567 | |
723 | |
568 | =head3 STATISTICAL INFORMATION |
724 | =head3 STATISTICAL INFORMATION |
569 | |
725 | |
… | |
… | |
614 | |
770 | |
615 | =head2 FORK BEHAVIOUR |
771 | =head2 FORK BEHAVIOUR |
616 | |
772 | |
617 | This module should do "the right thing" when the process using it forks: |
773 | This module should do "the right thing" when the process using it forks: |
618 | |
774 | |
619 | Before the fork, IO::AIO enters a quiescent state where no requests |
775 | Before the fork, BDB enters a quiescent state where no requests |
620 | can be added in other threads and no results will be processed. After |
776 | can be added in other threads and no results will be processed. After |
621 | the fork the parent simply leaves the quiescent state and continues |
777 | the fork the parent simply leaves the quiescent state and continues |
622 | request/result processing, while the child frees the request/result queue |
778 | request/result processing, while the child frees the request/result queue |
623 | (so that the requests started before the fork will only be handled in the |
779 | (so that the requests started before the fork will only be handled in the |
624 | parent). Threads will be started on demand until the limit set in the |
780 | parent). Threads will be started on demand until the limit set in the |
625 | parent process has been reached again. |
781 | parent process has been reached again. |
626 | |
782 | |
627 | In short: the parent will, after a short pause, continue as if fork had |
783 | In short: the parent will, after a short pause, continue as if fork had |
628 | not been called, while the child will act as if IO::AIO has not been used |
784 | not been called, while the child will act as if BDB has not been used |
629 | yet. |
785 | yet. |
|
|
786 | |
|
|
787 | Win32 note: there is no fork on win32, and perls emulation of it is too |
|
|
788 | broken to be supported, so do not use BDB in a windows pseudo-fork, better |
|
|
789 | yet, switch to a more capable platform. |
630 | |
790 | |
631 | =head2 MEMORY USAGE |
791 | =head2 MEMORY USAGE |
632 | |
792 | |
633 | Per-request usage: |
793 | Per-request usage: |
634 | |
794 | |
… | |
… | |
656 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
816 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
657 | above. |
817 | above. |
658 | |
818 | |
659 | =head1 SEE ALSO |
819 | =head1 SEE ALSO |
660 | |
820 | |
661 | L<Coro::AIO>. |
821 | L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural |
|
|
822 | syntax), L<IO::AIO> (nice to have). |
662 | |
823 | |
663 | =head1 AUTHOR |
824 | =head1 AUTHOR |
664 | |
825 | |
665 | Marc Lehmann <schmorp@schmorp.de> |
826 | Marc Lehmann <schmorp@schmorp.de> |
666 | http://home.schmorp.de/ |
827 | http://home.schmorp.de/ |