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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 | # automatic result processing with AnyEvent: |
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30 | our $FH; open $FH, "<&=" . BDB::poll_fileno; |
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31 | our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); |
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32 | |
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33 | # automatic result processing with EV: |
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34 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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35 | |
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36 | # with Glib: |
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37 | add_watch Glib::IO BDB::poll_fileno, |
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38 | in => sub { BDB::poll_cb; 1 }; |
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39 | |
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40 | # or simply flush manually |
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41 | BDB::flush; |
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42 | |
8 | |
43 | |
9 | =head1 DESCRIPTION |
44 | =head1 DESCRIPTION |
10 | |
45 | |
11 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
46 | 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). |
47 | The BDB API is very similar to the C API (the translation has been very faithful). |
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72 | use strict 'vars'; |
107 | use strict 'vars'; |
73 | |
108 | |
74 | use base 'Exporter'; |
109 | use base 'Exporter'; |
75 | |
110 | |
76 | BEGIN { |
111 | BEGIN { |
77 | our $VERSION = '1.0'; |
112 | our $VERSION = '1.2'; |
78 | |
113 | |
79 | our @BDB_REQ = qw( |
114 | our @BDB_REQ = qw( |
80 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
115 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
81 | db_env_memp_sync db_env_memp_trickle |
116 | db_env_memp_sync db_env_memp_trickle |
82 | db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range |
117 | db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range |
83 | db_txn_commit db_txn_abort |
118 | 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 |
119 | 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 |
120 | db_sequence_open db_sequence_close |
86 | db_sequence_get db_sequence_remove |
121 | db_sequence_get db_sequence_remove |
87 | ); |
122 | ); |
88 | our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); |
123 | our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); |
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126 | =head3 BDB functions |
161 | =head3 BDB functions |
127 | |
162 | |
128 | Functions in the BDB namespace, exported by default: |
163 | Functions in the BDB namespace, exported by default: |
129 | |
164 | |
130 | $env = db_env_create (U32 env_flags = 0) |
165 | $env = db_env_create (U32 env_flags = 0) |
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166 | flags: RPCCLIENT |
131 | |
167 | |
132 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
168 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
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169 | 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 |
133 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
170 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
134 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
171 | db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
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172 | flags: FORCE |
135 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
173 | db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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174 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
136 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
175 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
137 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
176 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
138 | |
177 | |
139 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
178 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
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179 | flags: XA_CREATE |
140 | |
180 | |
141 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
181 | db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
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182 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
142 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
183 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
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184 | flags: DB_NOSYNC |
143 | 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) |
185 | 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) |
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186 | flags: FREELIST_ONLY FREE_SPACE |
144 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
187 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
145 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
188 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
146 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
189 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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190 | flags: APPEND NODUPDATA NOOVERWRITE |
147 | db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
191 | db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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192 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
148 | db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
193 | db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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194 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
149 | db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
195 | db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
150 | db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
196 | db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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197 | flags: TXN_NOSYNC TXN_SYNC |
151 | db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) |
198 | db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) |
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199 | |
152 | db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) |
200 | db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) |
153 | db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) |
201 | db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) |
154 | db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
202 | db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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203 | flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA |
155 | db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
204 | db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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205 | flags: CURRENT FIRST GET_BOTH GET_BOTH_RANGE GET_RECNO JOIN_ITEM LAST NEXT NEXT_DUP NEXT_NODUP PREV PREV_DUP PREV_NODUP SET SET_RANGE SET_RECNO READ_UNCOMMITTED MULTIPLE MULTIPLE_KEY RMW |
156 | db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
206 | db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
157 | db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) |
207 | db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) |
158 | |
208 | |
159 | db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
209 | db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
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210 | flags: CREATE EXCL |
160 | db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) |
211 | db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) |
161 | db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = &PL_sv_undef) |
212 | db_sequence_get (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, int delta, SV *seq_value, U32 flags = DB_TXN_NOSYNC, SV *callback = &PL_sv_undef) |
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213 | flags: TXN_NOSYNC |
162 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
214 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
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215 | flags: TXN_NOSYNC |
163 | |
216 | |
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217 | =head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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218 | |
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219 | This is not actually a Berkeley DB function but a BDB module |
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220 | extension. The background for this exytension is: It is very annoying to |
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221 | have to check every single BDB function for error returns and provide a |
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222 | codepath out of your transaction. While the BDB module still makes this |
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223 | possible, it contains the following extensions: |
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224 | |
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225 | When a transaction-protected function returns any operating system |
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226 | error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the |
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227 | transaction. This flag is also set by Berkeley DB functions themselves |
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228 | when an operation fails with LOCK_DEADLOCK, and it causes all further |
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229 | operations on that transaction (including C<db_txn_commit>) to fail. |
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230 | |
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231 | The C<db_txn_finish> request will look at this flag, and, if it is set, |
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232 | will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> |
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233 | if it isn't set to something else yet). If it isn't set, it will call |
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234 | C<db_txn_commit> and return the error normally. |
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235 | |
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236 | How to use this? Easy: just write your transaction normally: |
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237 | |
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238 | my $txn = $db_env->txn_begin; |
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239 | db_get $db, $txn, "key", my $data; |
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240 | db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND; |
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241 | db_txn_finish $txn; |
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242 | die "transaction failed" if $!; |
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243 | |
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244 | That is, handle only the expected errors. If something unexpected happens |
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245 | (EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining |
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246 | requests (db_put in this case) will simply be skipped (they will fail with |
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247 | LOCK_DEADLOCK) and the transaction will be aborted. |
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248 | |
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249 | You can use the C<< $txn->failed >> method to check wether a transaction |
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250 | has failed in this way and abort further processing (excluding |
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251 | C<db_txn_finish>). |
164 | |
252 | |
165 | =head3 DB_ENV/database environment methods |
253 | =head3 DB_ENV/database environment methods |
166 | |
254 | |
167 | Methods available on DB_ENV/$env handles: |
255 | Methods available on DB_ENV/$env handles: |
168 | |
256 | |
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179 | $int = $env->set_flags (U32 flags, int onoff) |
267 | $int = $env->set_flags (U32 flags, int onoff) |
180 | $env->set_errfile (FILE *errfile = 0) |
268 | $env->set_errfile (FILE *errfile = 0) |
181 | $env->set_msgfile (FILE *msgfile = 0) |
269 | $env->set_msgfile (FILE *msgfile = 0) |
182 | $int = $env->set_verbose (U32 which, int onoff = 1) |
270 | $int = $env->set_verbose (U32 which, int onoff = 1) |
183 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
271 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
184 | $int = $env->set_timeout (NV timeout, U32 flags) |
272 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
185 | $int = $env->set_mp_max_openfd (int maxopenfd); |
273 | $int = $env->set_mp_max_openfd (int maxopenfd); |
186 | $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); |
274 | $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); |
187 | $int = $env->set_mp_mmapsize (int mmapsize_mb) |
275 | $int = $env->set_mp_mmapsize (int mmapsize_mb) |
188 | $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) |
276 | $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) |
189 | $int = $env->set_lk_max_lockers (U32 max) |
277 | $int = $env->set_lk_max_lockers (U32 max) |
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191 | $int = $env->set_lk_max_objects (U32 max) |
279 | $int = $env->set_lk_max_objects (U32 max) |
192 | $int = $env->set_lg_bsize (U32 max) |
280 | $int = $env->set_lg_bsize (U32 max) |
193 | $int = $env->set_lg_max (U32 max) |
281 | $int = $env->set_lg_max (U32 max) |
194 | |
282 | |
195 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
283 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
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284 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
196 | |
285 | |
197 | =head4 Example: |
286 | =head4 Example: |
198 | |
287 | |
199 | use AnyEvent; |
288 | use AnyEvent; |
200 | use BDB; |
289 | use BDB; |
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229 | SvREFCNT_dec (env); |
318 | SvREFCNT_dec (env); |
230 | } |
319 | } |
231 | |
320 | |
232 | $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
321 | $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
233 | $int = $db->set_flags (U32 flags) |
322 | $int = $db->set_flags (U32 flags) |
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323 | flags: CHKSUM ENCRYPT TXN_NOT_DURABLE |
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324 | Btree: DUP DUPSORT RECNUM REVSPLITOFF |
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325 | Hash: DUP DUPSORT |
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326 | Queue: INORDER |
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327 | Recno: RENUMBER SNAPSHOT |
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328 | |
234 | $int = $db->set_encrypt (const char *password, U32 flags) |
329 | $int = $db->set_encrypt (const char *password, U32 flags) |
235 | $int = $db->set_lorder (int lorder) |
330 | $int = $db->set_lorder (int lorder) |
236 | $int = $db->set_bt_minkey (U32 minkey) |
331 | $int = $db->set_bt_minkey (U32 minkey) |
237 | $int = $db->set_re_delim (int delim) |
332 | $int = $db->set_re_delim (int delim) |
238 | $int = $db->set_re_pad (int re_pad) |
333 | $int = $db->set_re_pad (int re_pad) |
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241 | $int = $db->set_h_ffactor (U32 h_ffactor) |
336 | $int = $db->set_h_ffactor (U32 h_ffactor) |
242 | $int = $db->set_h_nelem (U32 h_nelem) |
337 | $int = $db->set_h_nelem (U32 h_nelem) |
243 | $int = $db->set_q_extentsize (U32 extentsize) |
338 | $int = $db->set_q_extentsize (U32 extentsize) |
244 | |
339 | |
245 | $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) |
340 | $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) |
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341 | flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT |
246 | $seq = $db->sequence (U32 flags = 0) |
342 | $seq = $db->sequence (U32 flags = 0) |
247 | |
343 | |
248 | =head4 Example: |
344 | =head4 Example: |
249 | |
345 | |
250 | my $db = db_create $env; |
346 | my $db = db_create $env; |
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269 | DESTROY (DB_TXN_ornull *txn) |
365 | DESTROY (DB_TXN_ornull *txn) |
270 | CODE: |
366 | CODE: |
271 | if (txn) |
367 | if (txn) |
272 | txn->abort (txn); |
368 | txn->abort (txn); |
273 | |
369 | |
274 | $int = $txn->set_timeout (NV timeout, U32 flags) |
370 | $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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371 | flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT |
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372 | |
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373 | $bool = $txn->failed |
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374 | # see db_txn_finish documentation, above |
275 | |
375 | |
276 | |
376 | |
277 | =head3 DBC/cursor methods |
377 | =head3 DBC/cursor methods |
278 | |
378 | |
279 | Methods available on DBC/$dbc handles: |
379 | Methods available on DBC/$dbc handles: |
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306 | seq->close (seq, 0); |
406 | seq->close (seq, 0); |
307 | |
407 | |
308 | $int = $seq->initial_value (db_seq_t value) |
408 | $int = $seq->initial_value (db_seq_t value) |
309 | $int = $seq->set_cachesize (U32 size) |
409 | $int = $seq->set_cachesize (U32 size) |
310 | $int = $seq->set_flags (U32 flags) |
410 | $int = $seq->set_flags (U32 flags) |
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411 | flags: SEQ_DEC SEQ_INC SEQ_WRAP |
311 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
412 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
312 | |
413 | |
313 | =head4 Example: |
414 | =head4 Example: |
314 | |
415 | |
315 | my $seq = $db->sequence; |
416 | my $seq = $db->sequence; |
… | |
… | |
369 | interactiveness when perl is not fast enough to process all requests in |
470 | interactiveness when perl is not fast enough to process all requests in |
370 | time. |
471 | time. |
371 | |
472 | |
372 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
473 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
373 | |
474 | |
374 | Example: Install an Event watcher that automatically calls |
475 | Example: Install an EV watcher that automatically calls |
375 | BDB::poll_cb with low priority, to ensure that other parts of the |
476 | BDB::poll_cb with low priority, to ensure that other parts of the |
376 | program get the CPU sometimes even under high AIO load. |
477 | program get the CPU sometimes even under high load. |
377 | |
478 | |
378 | # try not to spend much more than 0.1s in poll_cb |
479 | # try not to spend much more than 0.1s in poll_cb |
379 | BDB::max_poll_time 0.1; |
480 | BDB::max_poll_time 0.1; |
380 | |
481 | |
381 | # use a low priority so other tasks have priority |
482 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
382 | Event->io (fd => BDB::poll_fileno, |
|
|
383 | poll => 'r', nice => 1, |
|
|
384 | cb => &BDB::poll_cb); |
|
|
385 | |
483 | |
386 | =item BDB::poll_wait |
484 | =item BDB::poll_wait |
387 | |
485 | |
388 | If there are any outstanding requests and none of them in the result |
486 | If there are any outstanding requests and none of them in the result |
389 | phase, wait till the result filehandle becomes ready for reading (simply |
487 | phase, wait till the result filehandle becomes ready for reading (simply |
… | |
… | |
401 | |
499 | |
402 | BDB::poll_wait, BDB::poll_cb |
500 | BDB::poll_wait, BDB::poll_cb |
403 | |
501 | |
404 | =item BDB::flush |
502 | =item BDB::flush |
405 | |
503 | |
406 | Wait till all outstanding AIO requests have been handled. |
504 | Wait till all outstanding BDB requests have been handled. |
407 | |
505 | |
408 | Strictly equivalent to: |
506 | Strictly equivalent to: |
409 | |
507 | |
410 | BDB::poll_wait, BDB::poll_cb |
508 | BDB::poll_wait, BDB::poll_cb |
411 | while BDB::nreqs; |
509 | while BDB::nreqs; |
… | |
… | |
416 | |
514 | |
417 | =over 4 |
515 | =over 4 |
418 | |
516 | |
419 | =item BDB::min_parallel $nthreads |
517 | =item BDB::min_parallel $nthreads |
420 | |
518 | |
421 | Set the minimum number of AIO threads to C<$nthreads>. The current |
519 | Set the minimum number of BDB threads to C<$nthreads>. The current |
422 | default is C<8>, which means eight asynchronous operations can execute |
520 | default is C<8>, which means eight asynchronous operations can execute |
423 | concurrently at any one time (the number of outstanding requests, |
521 | concurrently at any one time (the number of outstanding requests, |
424 | however, is unlimited). |
522 | however, is unlimited). |
425 | |
523 | |
426 | BDB starts threads only on demand, when an AIO request is queued and |
524 | BDB starts threads only on demand, when an BDB request is queued and |
427 | no free thread exists. Please note that queueing up a hundred requests can |
525 | no free thread exists. Please note that queueing up a hundred requests can |
428 | create demand for a hundred threads, even if it turns out that everything |
526 | create demand for a hundred threads, even if it turns out that everything |
429 | is in the cache and could have been processed faster by a single thread. |
527 | is in the cache and could have been processed faster by a single thread. |
430 | |
528 | |
431 | It is recommended to keep the number of threads relatively low, as some |
529 | It is recommended to keep the number of threads relatively low, as some |
… | |
… | |
436 | Under most circumstances you don't need to call this function, as the |
534 | Under most circumstances you don't need to call this function, as the |
437 | module selects a default that is suitable for low to moderate load. |
535 | module selects a default that is suitable for low to moderate load. |
438 | |
536 | |
439 | =item BDB::max_parallel $nthreads |
537 | =item BDB::max_parallel $nthreads |
440 | |
538 | |
441 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
539 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
442 | specified number of threads are currently running, this function kills |
540 | specified number of threads are currently running, this function kills |
443 | them. This function blocks until the limit is reached. |
541 | them. This function blocks until the limit is reached. |
444 | |
542 | |
445 | While C<$nthreads> are zero, aio requests get queued but not executed |
543 | While C<$nthreads> are zero, aio requests get queued but not executed |
446 | until the number of threads has been increased again. |
544 | until the number of threads has been increased again. |
… | |
… | |
549 | |
647 | |
550 | =head2 FORK BEHAVIOUR |
648 | =head2 FORK BEHAVIOUR |
551 | |
649 | |
552 | This module should do "the right thing" when the process using it forks: |
650 | This module should do "the right thing" when the process using it forks: |
553 | |
651 | |
554 | Before the fork, IO::AIO enters a quiescent state where no requests |
652 | Before the fork, BDB enters a quiescent state where no requests |
555 | can be added in other threads and no results will be processed. After |
653 | can be added in other threads and no results will be processed. After |
556 | the fork the parent simply leaves the quiescent state and continues |
654 | the fork the parent simply leaves the quiescent state and continues |
557 | request/result processing, while the child frees the request/result queue |
655 | request/result processing, while the child frees the request/result queue |
558 | (so that the requests started before the fork will only be handled in the |
656 | (so that the requests started before the fork will only be handled in the |
559 | parent). Threads will be started on demand until the limit set in the |
657 | parent). Threads will be started on demand until the limit set in the |
560 | parent process has been reached again. |
658 | parent process has been reached again. |
561 | |
659 | |
562 | In short: the parent will, after a short pause, continue as if fork had |
660 | In short: the parent will, after a short pause, continue as if fork had |
563 | not been called, while the child will act as if IO::AIO has not been used |
661 | not been called, while the child will act as if BDB has not been used |
564 | yet. |
662 | yet. |
565 | |
663 | |
566 | =head2 MEMORY USAGE |
664 | =head2 MEMORY USAGE |
567 | |
665 | |
568 | Per-request usage: |
666 | Per-request usage: |
… | |
… | |
571 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
669 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
572 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
670 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
573 | scalars and other data passed into aio requests will also be locked and |
671 | scalars and other data passed into aio requests will also be locked and |
574 | will consume memory till the request has entered the done state. |
672 | will consume memory till the request has entered the done state. |
575 | |
673 | |
576 | This is now awfully much, so queuing lots of requests is not usually a |
674 | This is not awfully much, so queuing lots of requests is not usually a |
577 | problem. |
675 | problem. |
578 | |
676 | |
579 | Per-thread usage: |
677 | Per-thread usage: |
580 | |
678 | |
581 | In the execution phase, some aio requests require more memory for |
679 | In the execution phase, some aio requests require more memory for |
582 | temporary buffers, and each thread requires a stack and other data |
680 | temporary buffers, and each thread requires a stack and other data |
583 | structures (usually around 16k-128k, depending on the OS). |
681 | structures (usually around 16k-128k, depending on the OS). |
584 | |
682 | |
585 | =head1 KNOWN BUGS |
683 | =head1 KNOWN BUGS |
586 | |
684 | |
587 | Known bugs will be fixed in the next release. |
685 | Known bugs will be fixed in the next release, except: |
|
|
686 | |
|
|
687 | If you use a transaction in any request, and the request returns |
|
|
688 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
|
|
689 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
|
|
690 | above. |
588 | |
691 | |
589 | =head1 SEE ALSO |
692 | =head1 SEE ALSO |
590 | |
693 | |
591 | L<Coro::AIO>. |
694 | L<Coro::BDB>, L<IO::AIO>. |
592 | |
695 | |
593 | =head1 AUTHOR |
696 | =head1 AUTHOR |
594 | |
697 | |
595 | Marc Lehmann <schmorp@schmorp.de> |
698 | Marc Lehmann <schmorp@schmorp.de> |
596 | http://home.schmorp.de/ |
699 | http://home.schmorp.de/ |