… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use BDB; |
7 | use BDB; |
8 | |
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 | |
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45 | |
9 | =head1 DESCRIPTION |
46 | =head1 DESCRIPTION |
10 | |
47 | |
11 | =head2 EXAMPLE |
48 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
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49 | The BDB API is very similar to the C API (the translation has been very faithful). |
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50 | |
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51 | See also the example sections in the document below and possibly the eg/ |
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52 | subdirectory of the BDB distribution. Last not least see the IO::AIO |
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53 | documentation, as that module uses almost the same asynchronous request |
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54 | model as this module. |
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55 | |
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56 | I know this is woefully inadequate documentation. Send a patch! |
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57 | |
12 | |
58 | |
13 | =head1 REQUEST ANATOMY AND LIFETIME |
59 | =head1 REQUEST ANATOMY AND LIFETIME |
14 | |
60 | |
15 | Every request method creates a request. which is a C data structure not |
61 | Every request method creates a request. which is a C data structure not |
16 | directly visible to Perl. |
62 | directly visible to Perl. |
… | |
… | |
63 | use strict 'vars'; |
109 | use strict 'vars'; |
64 | |
110 | |
65 | use base 'Exporter'; |
111 | use base 'Exporter'; |
66 | |
112 | |
67 | BEGIN { |
113 | BEGIN { |
68 | our $VERSION = '0.1'; |
114 | our $VERSION = '1.6'; |
69 | |
115 | |
70 | our @BDB_REQ = qw( |
116 | our @BDB_REQ = qw( |
71 | db_env_create db_env_open db_env_close |
117 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
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118 | db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove |
72 | db_create db_open db_close db_compact db_sync db_put db_get db_pget db_del |
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 |
73 | db_txn_commit db_txn_abort |
121 | db_txn_commit db_txn_abort db_txn_finish |
74 | 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 |
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123 | db_sequence_open db_sequence_close |
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124 | db_sequence_get db_sequence_remove |
75 | ); |
125 | ); |
76 | our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice)); |
126 | our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); |
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127 | our @EXPORT_OK = qw( |
77 | our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush |
128 | poll_fileno poll_cb poll_wait flush |
78 | min_parallel max_parallel max_idle |
129 | min_parallel max_parallel max_idle |
79 | nreqs nready npending nthreads |
130 | nreqs nready npending nthreads |
80 | max_poll_time max_poll_reqs); |
131 | max_poll_time max_poll_reqs |
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132 | ); |
81 | |
133 | |
82 | require XSLoader; |
134 | require XSLoader; |
83 | XSLoader::load ("BDB", $VERSION); |
135 | XSLoader::load ("BDB", $VERSION); |
84 | } |
136 | } |
85 | |
137 | |
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138 | =head2 WIN32 FILENAMES/DATABASE NAME MESS |
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139 | |
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140 | Perl on Win32 supports only ASCII filenames (the reason is that it abuses |
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141 | an internal flag to store wether a filename is Unicode or ANSI, but that |
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142 | flag is used for somethign else in the perl core, so there is no way to |
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143 | detect wether a filename is ANSI or Unicode-encoded). The BDB module |
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144 | tries to work around this issue by assuming that the filename is an ANSI |
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145 | filename and BDB was built for unicode support. |
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146 | |
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147 | =head2 BERKELEYDB FUNCTIONS |
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148 | |
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149 | All of these are functions. The create functions simply return a new |
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150 | object and never block. All the remaining functions take an optional |
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151 | callback as last argument. If it is missing, then the function will be |
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152 | executed synchronously. In both cases, C<$!> will reflect the return value |
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153 | of the function. |
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154 | |
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155 | BDB functions that cannot block (mostly functions that manipulate |
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156 | settings) are method calls on the relevant objects, so the rule of thumb |
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157 | is: if it's a method, it's not blocking, if it's a function, it takes a |
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158 | callback as last argument. |
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159 | |
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160 | In the following, C<$int> signifies an integer return value, |
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161 | C<bdb_filename> is a "filename" (octets on unix, madness on windows), |
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162 | C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a |
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163 | floating point value. |
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164 | |
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165 | The C<SV *> types are generic perl scalars (for input and output of data |
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166 | values), and the C<SV *callback> is the optional callback function to call |
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167 | when the request is completed. |
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168 | |
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169 | The various C<DB_ENV> etc. arguments are handles return by |
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170 | C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an |
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171 | appended C<_ornull> this means they are optional and you can pass C<undef> |
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172 | for them, resulting a NULL pointer on the C level. |
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173 | |
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174 | =head3 BDB functions |
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175 | |
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176 | Functions in the BDB namespace, exported by default: |
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177 | |
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178 | $env = db_env_create (U32 env_flags = 0) |
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179 | flags: RPCCLIENT |
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180 | |
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181 | db_env_open (DB_ENV *env, bdb_filename db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
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182 | 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 |
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183 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
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184 | 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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185 | flags: FORCE |
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186 | 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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187 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
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188 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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189 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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190 | 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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191 | 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) |
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192 | |
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193 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
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194 | flags: XA_CREATE |
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195 | |
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196 | 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) |
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197 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
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198 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
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199 | flags: DB_NOSYNC |
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200 | db_upgrade (DB *db, bdb_filename file, U32 flags = 0, SV *callback = &PL_sv_undef) |
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201 | 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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202 | flags: FREELIST_ONLY FREE_SPACE |
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203 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
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204 | db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, U32 flags = 0, SV *callback = &PL_sv_undef) |
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205 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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206 | flags: APPEND NODUPDATA NOOVERWRITE |
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207 | db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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208 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
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209 | 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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210 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
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211 | db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
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212 | db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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213 | flags: TXN_NOSYNC TXN_SYNC |
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214 | db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) |
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215 | |
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216 | db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) |
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217 | db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) |
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218 | db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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219 | flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA |
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220 | db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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221 | 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 |
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222 | db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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223 | db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) |
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224 | |
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225 | db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
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226 | flags: CREATE EXCL |
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227 | db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) |
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228 | 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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229 | flags: TXN_NOSYNC |
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230 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
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231 | flags: TXN_NOSYNC |
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232 | |
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233 | =head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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234 | |
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235 | This is not actually a Berkeley DB function but a BDB module |
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236 | extension. The background for this exytension is: It is very annoying to |
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237 | have to check every single BDB function for error returns and provide a |
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238 | codepath out of your transaction. While the BDB module still makes this |
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239 | possible, it contains the following extensions: |
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240 | |
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241 | When a transaction-protected function returns any operating system |
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242 | error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the |
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243 | transaction. This flag is also set by Berkeley DB functions themselves |
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244 | when an operation fails with LOCK_DEADLOCK, and it causes all further |
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245 | operations on that transaction (including C<db_txn_commit>) to fail. |
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246 | |
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247 | The C<db_txn_finish> request will look at this flag, and, if it is set, |
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248 | will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> |
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249 | if it isn't set to something else yet). If it isn't set, it will call |
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250 | C<db_txn_commit> and return the error normally. |
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251 | |
|
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252 | How to use this? Easy: just write your transaction normally: |
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253 | |
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254 | my $txn = $db_env->txn_begin; |
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255 | db_get $db, $txn, "key", my $data; |
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256 | db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND; |
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257 | db_txn_finish $txn; |
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258 | die "transaction failed" if $!; |
|
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259 | |
|
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260 | That is, handle only the expected errors. If something unexpected happens |
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261 | (EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining |
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262 | requests (db_put in this case) will simply be skipped (they will fail with |
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263 | LOCK_DEADLOCK) and the transaction will be aborted. |
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264 | |
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265 | You can use the C<< $txn->failed >> method to check wether a transaction |
|
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266 | has failed in this way and abort further processing (excluding |
|
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267 | C<db_txn_finish>). |
|
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268 | |
|
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269 | =head3 DB_ENV/database environment methods |
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270 | |
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271 | Methods available on DB_ENV/$env handles: |
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272 | |
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273 | DESTROY (DB_ENV_ornull *env) |
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274 | CODE: |
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275 | if (env) |
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276 | env->close (env, 0); |
|
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277 | |
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278 | $int = $env->set_data_dir (const char *dir) |
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279 | $int = $env->set_tmp_dir (const char *dir) |
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280 | $int = $env->set_lg_dir (const char *dir) |
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281 | $int = $env->set_shm_key (long shm_key) |
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282 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
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283 | $int = $env->set_flags (U32 flags, int onoff = 1) |
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284 | $int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7] |
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285 | $int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7] |
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286 | $env->set_errfile (FILE *errfile = 0) |
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287 | $env->set_msgfile (FILE *msgfile = 0) |
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288 | $int = $env->set_verbose (U32 which, int onoff = 1) |
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289 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
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290 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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291 | $int = $env->set_mp_max_openfd (int maxopenfd); |
|
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292 | $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); |
|
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293 | $int = $env->set_mp_mmapsize (int mmapsize_mb) |
|
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294 | $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) |
|
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295 | $int = $env->set_lk_max_lockers (U32 max) |
|
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296 | $int = $env->set_lk_max_locks (U32 max) |
|
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297 | $int = $env->set_lk_max_objects (U32 max) |
|
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298 | $int = $env->set_lg_bsize (U32 max) |
|
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299 | $int = $env->set_lg_max (U32 max) |
|
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300 | $int = $env->mutex_set_increment (U32 increment) |
|
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301 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
|
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302 | $int = $env->mutex_set_max (U32 max) |
|
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303 | $int = $env->mutex_set_align (U32 align) |
|
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304 | |
|
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305 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
|
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306 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
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307 | |
|
|
308 | =head4 Example: |
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309 | |
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310 | use AnyEvent; |
|
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311 | use BDB; |
|
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312 | |
|
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313 | our $FH; open $FH, "<&=" . BDB::poll_fileno; |
|
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314 | our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); |
|
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315 | |
|
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316 | BDB::min_parallel 8; |
|
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317 | |
|
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318 | my $env = db_env_create; |
|
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319 | |
|
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320 | mkdir "bdtest", 0700; |
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321 | db_env_open |
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322 | $env, |
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323 | "bdtest", |
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324 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
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325 | 0600; |
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326 | |
|
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327 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
|
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328 | |
|
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329 | |
|
|
330 | =head3 DB/database methods |
|
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331 | |
|
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332 | Methods available on DB/$db handles: |
|
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333 | |
|
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334 | DESTROY (DB_ornull *db) |
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335 | CODE: |
|
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336 | if (db) |
|
|
337 | { |
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338 | SV *env = (SV *)db->app_private; |
|
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339 | db->close (db, 0); |
|
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340 | SvREFCNT_dec (env); |
|
|
341 | } |
|
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342 | |
|
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343 | $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
|
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344 | $int = $db->set_flags (U32 flags) |
|
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345 | flags: CHKSUM ENCRYPT TXN_NOT_DURABLE |
|
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346 | Btree: DUP DUPSORT RECNUM REVSPLITOFF |
|
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347 | Hash: DUP DUPSORT |
|
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348 | Queue: INORDER |
|
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349 | Recno: RENUMBER SNAPSHOT |
|
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350 | |
|
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351 | $int = $db->set_encrypt (const char *password, U32 flags) |
|
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352 | $int = $db->set_lorder (int lorder) |
|
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353 | $int = $db->set_bt_minkey (U32 minkey) |
|
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354 | $int = $db->set_re_delim (int delim) |
|
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355 | $int = $db->set_re_pad (int re_pad) |
|
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356 | $int = $db->set_re_source (char *source) |
|
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357 | $int = $db->set_re_len (U32 re_len) |
|
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358 | $int = $db->set_h_ffactor (U32 h_ffactor) |
|
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359 | $int = $db->set_h_nelem (U32 h_nelem) |
|
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360 | $int = $db->set_q_extentsize (U32 extentsize) |
|
|
361 | |
|
|
362 | $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) |
|
|
363 | flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT |
|
|
364 | $seq = $db->sequence (U32 flags = 0) |
|
|
365 | |
|
|
366 | =head4 Example: |
|
|
367 | |
|
|
368 | my $db = db_create $env; |
|
|
369 | db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; |
|
|
370 | |
|
|
371 | for (1..1000) { |
|
|
372 | db_put $db, undef, "key $_", "data $_"; |
|
|
373 | |
|
|
374 | db_key_range $db, undef, "key $_", my $keyrange; |
|
|
375 | my ($lt, $eq, $gt) = @$keyrange; |
|
|
376 | } |
|
|
377 | |
|
|
378 | db_del $db, undef, "key $_" for 1..1000; |
|
|
379 | |
|
|
380 | db_sync $db; |
|
|
381 | |
|
|
382 | |
|
|
383 | =head3 DB_TXN/transaction methods |
|
|
384 | |
|
|
385 | Methods available on DB_TXN/$txn handles: |
|
|
386 | |
|
|
387 | DESTROY (DB_TXN_ornull *txn) |
|
|
388 | CODE: |
|
|
389 | if (txn) |
|
|
390 | txn->abort (txn); |
|
|
391 | |
|
|
392 | $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
|
|
393 | flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT |
|
|
394 | |
|
|
395 | $bool = $txn->failed |
|
|
396 | # see db_txn_finish documentation, above |
|
|
397 | |
|
|
398 | |
|
|
399 | =head3 DBC/cursor methods |
|
|
400 | |
|
|
401 | Methods available on DBC/$dbc handles: |
|
|
402 | |
|
|
403 | DESTROY (DBC_ornull *dbc) |
|
|
404 | CODE: |
|
|
405 | if (dbc) |
|
|
406 | dbc->c_close (dbc); |
|
|
407 | |
|
|
408 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
|
|
409 | |
|
|
410 | =head4 Example: |
|
|
411 | |
|
|
412 | my $c = $db->cursor; |
|
|
413 | |
|
|
414 | for (;;) { |
|
|
415 | db_c_get $c, my $key, my $data, BDB::NEXT; |
|
|
416 | warn "<$!,$key,$data>"; |
|
|
417 | last if $!; |
|
|
418 | } |
|
|
419 | |
|
|
420 | db_c_close $c; |
|
|
421 | |
|
|
422 | |
|
|
423 | =head3 DB_SEQUENCE/sequence methods |
|
|
424 | |
|
|
425 | Methods available on DB_SEQUENCE/$seq handles: |
|
|
426 | |
|
|
427 | DESTROY (DB_SEQUENCE_ornull *seq) |
|
|
428 | CODE: |
|
|
429 | if (seq) |
|
|
430 | seq->close (seq, 0); |
|
|
431 | |
|
|
432 | $int = $seq->initial_value (db_seq_t value) |
|
|
433 | $int = $seq->set_cachesize (U32 size) |
|
|
434 | $int = $seq->set_flags (U32 flags) |
|
|
435 | flags: SEQ_DEC SEQ_INC SEQ_WRAP |
|
|
436 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
|
|
437 | |
|
|
438 | =head4 Example: |
|
|
439 | |
|
|
440 | my $seq = $db->sequence; |
|
|
441 | |
|
|
442 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
|
|
443 | db_sequence_get $seq, undef, 1, my $value; |
|
|
444 | |
|
|
445 | |
86 | =head2 SUPPORT FUNCTIONS |
446 | =head2 SUPPORT FUNCTIONS |
87 | |
447 | |
88 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
448 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
89 | |
449 | |
90 | =over 4 |
450 | =over 4 |
|
|
451 | |
|
|
452 | =item $msg = BDB::strerror [$errno] |
|
|
453 | |
|
|
454 | Returns the string corresponding to the given errno value. If no argument |
|
|
455 | is given, use C<$!>. |
|
|
456 | |
|
|
457 | Note that the BDB module also patches the C<$!> variable directly, so you |
|
|
458 | should be able to get a bdb error string by simply stringifying C<$!>. |
91 | |
459 | |
92 | =item $fileno = BDB::poll_fileno |
460 | =item $fileno = BDB::poll_fileno |
93 | |
461 | |
94 | Return the I<request result pipe file descriptor>. This filehandle must be |
462 | Return the I<request result pipe file descriptor>. This filehandle must be |
95 | polled for reading by some mechanism outside this module (e.g. Event or |
463 | polled for reading by some mechanism outside this module (e.g. Event or |
… | |
… | |
134 | interactiveness when perl is not fast enough to process all requests in |
502 | interactiveness when perl is not fast enough to process all requests in |
135 | time. |
503 | time. |
136 | |
504 | |
137 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
505 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
138 | |
506 | |
139 | Example: Install an Event watcher that automatically calls |
507 | Example: Install an EV watcher that automatically calls |
140 | BDB::poll_cb with low priority, to ensure that other parts of the |
508 | BDB::poll_cb with low priority, to ensure that other parts of the |
141 | program get the CPU sometimes even under high AIO load. |
509 | program get the CPU sometimes even under high load. |
142 | |
510 | |
143 | # try not to spend much more than 0.1s in poll_cb |
511 | # try not to spend much more than 0.1s in poll_cb |
144 | BDB::max_poll_time 0.1; |
512 | BDB::max_poll_time 0.1; |
145 | |
513 | |
146 | # use a low priority so other tasks have priority |
514 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
147 | Event->io (fd => BDB::poll_fileno, |
|
|
148 | poll => 'r', nice => 1, |
|
|
149 | cb => &BDB::poll_cb); |
|
|
150 | |
515 | |
151 | =item BDB::poll_wait |
516 | =item BDB::poll_wait |
152 | |
517 | |
153 | If there are any outstanding requests and none of them in the result |
518 | If there are any outstanding requests and none of them in the result |
154 | phase, wait till the result filehandle becomes ready for reading (simply |
519 | phase, wait till the result filehandle becomes ready for reading (simply |
… | |
… | |
166 | |
531 | |
167 | BDB::poll_wait, BDB::poll_cb |
532 | BDB::poll_wait, BDB::poll_cb |
168 | |
533 | |
169 | =item BDB::flush |
534 | =item BDB::flush |
170 | |
535 | |
171 | Wait till all outstanding AIO requests have been handled. |
536 | Wait till all outstanding BDB requests have been handled. |
172 | |
537 | |
173 | Strictly equivalent to: |
538 | Strictly equivalent to: |
174 | |
539 | |
175 | BDB::poll_wait, BDB::poll_cb |
540 | BDB::poll_wait, BDB::poll_cb |
176 | while BDB::nreqs; |
541 | while BDB::nreqs; |
177 | |
542 | |
|
|
543 | =back |
|
|
544 | |
|
|
545 | =head3 VERSION CHECKING |
|
|
546 | |
|
|
547 | BerkeleyDB comes in various versions, many of them have minor |
|
|
548 | incompatibilities. This means that traditional "at least version x.x" |
|
|
549 | checks are often not sufficient. |
|
|
550 | |
|
|
551 | Example: set the log_autoremove option in a way compatible with <v.47 and |
|
|
552 | v4.7. Note the use of & on the constants to avoid triggering a compiletime |
|
|
553 | bug when the symbol isn't available. |
|
|
554 | |
|
|
555 | $DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7; |
|
|
556 | $DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7; |
|
|
557 | |
|
|
558 | =over 4 |
|
|
559 | |
|
|
560 | =item BDB::VERSION |
|
|
561 | |
|
|
562 | The C<BDB::VERSION> function, when called without arguments, returns the |
|
|
563 | Berkeley DB version as a v-string (usually with 3 components). You should |
|
|
564 | use C<lt> and C<ge> operators exclusively to make comparisons. |
|
|
565 | |
|
|
566 | Example: check for at least version 4.7. |
|
|
567 | |
|
|
568 | BDB::VERSION ge v4.7 or die; |
|
|
569 | |
|
|
570 | =item BDB::VERSION min-version |
|
|
571 | |
|
|
572 | Returns true if the BDB version is at least the given version (specified |
|
|
573 | as a v-string), false otherwise. |
|
|
574 | |
|
|
575 | Example: check for at least version 4.5. |
|
|
576 | |
|
|
577 | BDB::VERSION v4.7 or die; |
|
|
578 | |
|
|
579 | =item BDB::VERSION min-version, max-version |
|
|
580 | |
|
|
581 | Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version) |
|
|
582 | and less then C<max-version>. |
|
|
583 | |
|
|
584 | Example: check wether version is strictly less then v4.7. |
|
|
585 | |
|
|
586 | BDB::VERSION v0, v4.7 |
|
|
587 | or die "version 4.7 is not yet supported"; |
|
|
588 | |
|
|
589 | =back |
|
|
590 | |
|
|
591 | =cut |
|
|
592 | |
|
|
593 | sub VERSION { |
|
|
594 | if (@_ > 0) { |
|
|
595 | return undef if VERSION_v lt $_[0]; |
|
|
596 | if (@_ > 1) { |
|
|
597 | return undef if VERSION_v ge $_[1]; |
|
|
598 | } |
|
|
599 | } |
|
|
600 | |
|
|
601 | VERSION_v |
|
|
602 | } |
|
|
603 | |
178 | =head3 CONTROLLING THE NUMBER OF THREADS |
604 | =head3 CONTROLLING THE NUMBER OF THREADS |
179 | |
605 | |
|
|
606 | =over 4 |
|
|
607 | |
180 | =item BDB::min_parallel $nthreads |
608 | =item BDB::min_parallel $nthreads |
181 | |
609 | |
182 | Set the minimum number of AIO threads to C<$nthreads>. The current |
610 | Set the minimum number of BDB threads to C<$nthreads>. The current |
183 | default is C<8>, which means eight asynchronous operations can execute |
611 | default is C<8>, which means eight asynchronous operations can execute |
184 | concurrently at any one time (the number of outstanding requests, |
612 | concurrently at any one time (the number of outstanding requests, |
185 | however, is unlimited). |
613 | however, is unlimited). |
186 | |
614 | |
187 | BDB starts threads only on demand, when an AIO request is queued and |
615 | BDB starts threads only on demand, when an BDB request is queued and |
188 | no free thread exists. Please note that queueing up a hundred requests can |
616 | no free thread exists. Please note that queueing up a hundred requests can |
189 | create demand for a hundred threads, even if it turns out that everything |
617 | create demand for a hundred threads, even if it turns out that everything |
190 | is in the cache and could have been processed faster by a single thread. |
618 | is in the cache and could have been processed faster by a single thread. |
191 | |
619 | |
192 | It is recommended to keep the number of threads relatively low, as some |
620 | It is recommended to keep the number of threads relatively low, as some |
… | |
… | |
197 | Under most circumstances you don't need to call this function, as the |
625 | Under most circumstances you don't need to call this function, as the |
198 | module selects a default that is suitable for low to moderate load. |
626 | module selects a default that is suitable for low to moderate load. |
199 | |
627 | |
200 | =item BDB::max_parallel $nthreads |
628 | =item BDB::max_parallel $nthreads |
201 | |
629 | |
202 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
630 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
203 | specified number of threads are currently running, this function kills |
631 | specified number of threads are currently running, this function kills |
204 | them. This function blocks until the limit is reached. |
632 | them. This function blocks until the limit is reached. |
205 | |
633 | |
206 | While C<$nthreads> are zero, aio requests get queued but not executed |
634 | While C<$nthreads> are zero, aio requests get queued but not executed |
207 | until the number of threads has been increased again. |
635 | until the number of threads has been increased again. |
… | |
… | |
246 | |
674 | |
247 | =item BDB::set_sync_prepare $cb |
675 | =item BDB::set_sync_prepare $cb |
248 | |
676 | |
249 | Sets a callback that is called whenever a request is created without an |
677 | Sets a callback that is called whenever a request is created without an |
250 | explicit callback. It has to return two code references. The first is used |
678 | explicit callback. It has to return two code references. The first is used |
251 | as the request callback, and the second is called to wait until the first |
679 | as the request callback (it should save the return status), and the second |
|
|
680 | is called to wait until the first callback has been called (it must set |
|
|
681 | C<$!> to the return status). |
|
|
682 | |
|
|
683 | This mechanism can be used to include BDB into other event mechanisms, |
|
|
684 | such as L<AnyEvent::BDB> or L<Coro::BDB>. |
|
|
685 | |
252 | callback has been called. The default implementation works like this: |
686 | The default implementation works like this: |
253 | |
687 | |
254 | sub { |
688 | sub { |
255 | my $status; |
689 | my $status; |
256 | ( |
690 | ( |
257 | sub { $status = $! }, |
691 | sub { $status = $! }, |
258 | sub { BDB::poll while !defined $status; $! = $status }, |
692 | sub { BDB::poll while !defined $status; $! = $status }, |
259 | ) |
693 | ) |
260 | } |
694 | } |
|
|
695 | |
|
|
696 | It simply blocks the process till the request has finished and then sets |
|
|
697 | C<$!> to the return value. This means that if you don't use a callback, |
|
|
698 | BDB will simply fall back to synchronous operations. |
261 | |
699 | |
262 | =back |
700 | =back |
263 | |
701 | |
264 | =head3 STATISTICAL INFORMATION |
702 | =head3 STATISTICAL INFORMATION |
265 | |
703 | |
… | |
… | |
310 | |
748 | |
311 | =head2 FORK BEHAVIOUR |
749 | =head2 FORK BEHAVIOUR |
312 | |
750 | |
313 | This module should do "the right thing" when the process using it forks: |
751 | This module should do "the right thing" when the process using it forks: |
314 | |
752 | |
315 | Before the fork, IO::AIO enters a quiescent state where no requests |
753 | Before the fork, BDB enters a quiescent state where no requests |
316 | can be added in other threads and no results will be processed. After |
754 | can be added in other threads and no results will be processed. After |
317 | the fork the parent simply leaves the quiescent state and continues |
755 | the fork the parent simply leaves the quiescent state and continues |
318 | request/result processing, while the child frees the request/result queue |
756 | request/result processing, while the child frees the request/result queue |
319 | (so that the requests started before the fork will only be handled in the |
757 | (so that the requests started before the fork will only be handled in the |
320 | parent). Threads will be started on demand until the limit set in the |
758 | parent). Threads will be started on demand until the limit set in the |
321 | parent process has been reached again. |
759 | parent process has been reached again. |
322 | |
760 | |
323 | In short: the parent will, after a short pause, continue as if fork had |
761 | In short: the parent will, after a short pause, continue as if fork had |
324 | not been called, while the child will act as if IO::AIO has not been used |
762 | not been called, while the child will act as if BDB has not been used |
325 | yet. |
763 | yet. |
|
|
764 | |
|
|
765 | Win32 note: there is no fork on win32, and perls emulation of it is too |
|
|
766 | broken to be supported, so do not use BDB in a windows pseudo-fork, better |
|
|
767 | yet, switch to a more capable platform. |
326 | |
768 | |
327 | =head2 MEMORY USAGE |
769 | =head2 MEMORY USAGE |
328 | |
770 | |
329 | Per-request usage: |
771 | Per-request usage: |
330 | |
772 | |
… | |
… | |
332 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
774 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
333 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
775 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
334 | scalars and other data passed into aio requests will also be locked and |
776 | scalars and other data passed into aio requests will also be locked and |
335 | will consume memory till the request has entered the done state. |
777 | will consume memory till the request has entered the done state. |
336 | |
778 | |
337 | This is now awfully much, so queuing lots of requests is not usually a |
779 | This is not awfully much, so queuing lots of requests is not usually a |
338 | problem. |
780 | problem. |
339 | |
781 | |
340 | Per-thread usage: |
782 | Per-thread usage: |
341 | |
783 | |
342 | In the execution phase, some aio requests require more memory for |
784 | In the execution phase, some aio requests require more memory for |
343 | temporary buffers, and each thread requires a stack and other data |
785 | temporary buffers, and each thread requires a stack and other data |
344 | structures (usually around 16k-128k, depending on the OS). |
786 | structures (usually around 16k-128k, depending on the OS). |
345 | |
787 | |
346 | =head1 KNOWN BUGS |
788 | =head1 KNOWN BUGS |
347 | |
789 | |
348 | Known bugs will be fixed in the next release. |
790 | Known bugs will be fixed in the next release, except: |
|
|
791 | |
|
|
792 | If you use a transaction in any request, and the request returns |
|
|
793 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
|
|
794 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
|
|
795 | above. |
349 | |
796 | |
350 | =head1 SEE ALSO |
797 | =head1 SEE ALSO |
351 | |
798 | |
352 | L<Coro::AIO>. |
799 | L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural |
|
|
800 | syntax), L<IO::AIO> (nice to have). |
353 | |
801 | |
354 | =head1 AUTHOR |
802 | =head1 AUTHOR |
355 | |
803 | |
356 | Marc Lehmann <schmorp@schmorp.de> |
804 | Marc Lehmann <schmorp@schmorp.de> |
357 | http://home.schmorp.de/ |
805 | http://home.schmorp.de/ |