1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | BDB::AIO - Asynchronous Berkeley DB access |
3 | BDB - Asynchronous Berkeley DB access |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use BDB::AIO; |
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 result processing with AnyEvent: |
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33 | our $FH; open $FH, "<&=" . BDB::poll_fileno; |
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34 | our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); |
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35 | |
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36 | # automatic result processing with EV: |
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37 | my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb; |
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38 | |
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39 | # with Glib: |
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40 | add_watch Glib::IO BDB::poll_fileno, |
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41 | in => sub { BDB::poll_cb; 1 }; |
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42 | |
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43 | # or simply flush manually |
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44 | BDB::flush; |
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45 | |
8 | |
46 | |
9 | =head1 DESCRIPTION |
47 | =head1 DESCRIPTION |
10 | |
48 | |
11 | =head2 EXAMPLE |
49 | See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). |
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50 | The BDB API is very similar to the C API (the translation has been very faithful). |
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51 | |
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52 | See also the example sections in the document below and possibly the eg/ |
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53 | subdirectory of the BDB distribution. Last not least see the IO::AIO |
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54 | documentation, as that module uses almost the same asynchronous request |
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55 | model as this module. |
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56 | |
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57 | I know this is woefully inadequate documentation. Send a patch! |
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58 | |
12 | |
59 | |
13 | =head1 REQUEST ANATOMY AND LIFETIME |
60 | =head1 REQUEST ANATOMY AND LIFETIME |
14 | |
61 | |
15 | Every request method creates a request. which is a C data structure not |
62 | Every request method creates a request. which is a C data structure not |
16 | directly visible to Perl. |
63 | directly visible to Perl. |
… | |
… | |
55 | |
102 | |
56 | =back |
103 | =back |
57 | |
104 | |
58 | =cut |
105 | =cut |
59 | |
106 | |
60 | package BDB::AIO; |
107 | package BDB; |
61 | |
108 | |
62 | no warnings; |
109 | no warnings; |
63 | use strict 'vars'; |
110 | use strict 'vars'; |
64 | |
111 | |
65 | use base 'Exporter'; |
112 | use base 'Exporter'; |
66 | |
113 | |
67 | BEGIN { |
114 | BEGIN { |
68 | our $VERSION = '0.1'; |
115 | our $VERSION = '1.41'; |
69 | |
116 | |
70 | our @BDB_REQ = qw(); |
117 | our @BDB_REQ = qw( |
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118 | db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect |
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119 | db_env_memp_sync db_env_memp_trickle |
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120 | db_open db_close db_compact db_sync db_upgrade |
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121 | db_put db_get db_pget db_del db_key_range |
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122 | db_txn_commit db_txn_abort db_txn_finish |
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123 | db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del |
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124 | db_sequence_open db_sequence_close |
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125 | db_sequence_get db_sequence_remove |
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126 | ); |
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127 | our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); |
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128 | our @EXPORT_OK = qw( |
71 | our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush |
129 | poll_fileno poll_cb poll_wait flush |
72 | min_parallel max_parallel max_idle |
130 | min_parallel max_parallel max_idle |
73 | nreqs nready npending nthreads |
131 | nreqs nready npending nthreads |
74 | max_poll_time max_poll_reqs); |
132 | max_poll_time max_poll_reqs |
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133 | ); |
75 | |
134 | |
76 | require XSLoader; |
135 | require XSLoader; |
77 | XSLoader::load ("BDB::AIO", $VERSION); |
136 | XSLoader::load ("BDB", $VERSION); |
78 | } |
137 | } |
79 | |
138 | |
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139 | =head2 BERKELEYDB FUNCTIONS |
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140 | |
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141 | All of these are functions. The create functions simply return a new |
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142 | object and never block. All the remaining functions all take an optional |
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143 | callback as last argument. If it is missing, then the function will be |
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144 | executed synchronously. In both cases, C<$!> will reflect the return value |
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145 | of the function. |
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146 | |
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147 | BDB functions that cannot block (mostly functions that manipulate |
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148 | settings) are method calls on the relevant objects, so the rule of thumb |
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149 | is: if its a method, its not blocking, if its a function, it takes a |
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150 | callback as last argument. |
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151 | |
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152 | In the following, C<$int> signifies an integer return value, |
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153 | C<octetstring> is a "binary string" (i.e. a perl string with no character |
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154 | indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some |
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155 | integer, C<NV> is a floating point value. |
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156 | |
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157 | The C<SV *> types are generic perl scalars (for input and output of data |
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158 | values), and the C<SV *callback> is the optional callback function to call |
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159 | when the request is completed. |
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160 | |
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161 | The various C<DB_ENV> etc. arguments are handles return by |
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162 | C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an |
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163 | appended C<_ornull> this means they are optional and you can pass C<undef> |
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164 | for them, resulting a NULL pointer on the C level. |
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165 | |
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166 | =head3 BDB functions |
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167 | |
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168 | Functions in the BDB namespace, exported by default: |
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169 | |
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170 | $env = db_env_create (U32 env_flags = 0) |
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171 | flags: RPCCLIENT |
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172 | |
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173 | db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) |
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174 | 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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175 | db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) |
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176 | 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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177 | flags: FORCE |
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178 | 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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179 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
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180 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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181 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
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182 | |
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183 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
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184 | flags: XA_CREATE |
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185 | |
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186 | 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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187 | flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE |
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188 | db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
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189 | flags: DB_NOSYNC |
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190 | db_upgrade (DB *db, octetstring file, U32 flags = 0, SV *callback = &PL_sv_undef) |
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191 | 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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192 | flags: FREELIST_ONLY FREE_SPACE |
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193 | db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) |
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194 | 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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195 | db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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196 | flags: APPEND NODUPDATA NOOVERWRITE |
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197 | db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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198 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
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199 | 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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200 | flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW |
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201 | db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
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202 | db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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203 | flags: TXN_NOSYNC TXN_SYNC |
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204 | db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) |
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205 | |
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206 | db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) |
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207 | db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) |
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208 | db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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209 | flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA |
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210 | db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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211 | 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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212 | db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) |
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213 | db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) |
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214 | |
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215 | db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) |
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216 | flags: CREATE EXCL |
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217 | db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) |
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218 | 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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219 | flags: TXN_NOSYNC |
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220 | db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) |
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221 | flags: TXN_NOSYNC |
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222 | |
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223 | =head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef) |
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224 | |
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225 | This is not actually a Berkeley DB function but a BDB module |
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226 | extension. The background for this exytension is: It is very annoying to |
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227 | have to check every single BDB function for error returns and provide a |
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228 | codepath out of your transaction. While the BDB module still makes this |
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229 | possible, it contains the following extensions: |
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230 | |
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231 | When a transaction-protected function returns any operating system |
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232 | error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the |
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233 | transaction. This flag is also set by Berkeley DB functions themselves |
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234 | when an operation fails with LOCK_DEADLOCK, and it causes all further |
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235 | operations on that transaction (including C<db_txn_commit>) to fail. |
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236 | |
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237 | The C<db_txn_finish> request will look at this flag, and, if it is set, |
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238 | will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK> |
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239 | if it isn't set to something else yet). If it isn't set, it will call |
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240 | C<db_txn_commit> and return the error normally. |
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241 | |
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242 | How to use this? Easy: just write your transaction normally: |
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243 | |
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244 | my $txn = $db_env->txn_begin; |
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245 | db_get $db, $txn, "key", my $data; |
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246 | db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND; |
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247 | db_txn_finish $txn; |
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248 | die "transaction failed" if $!; |
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249 | |
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250 | That is, handle only the expected errors. If something unexpected happens |
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251 | (EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining |
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252 | requests (db_put in this case) will simply be skipped (they will fail with |
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253 | LOCK_DEADLOCK) and the transaction will be aborted. |
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254 | |
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255 | You can use the C<< $txn->failed >> method to check wether a transaction |
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256 | has failed in this way and abort further processing (excluding |
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257 | C<db_txn_finish>). |
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258 | |
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259 | =head3 DB_ENV/database environment methods |
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260 | |
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261 | Methods available on DB_ENV/$env handles: |
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262 | |
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263 | DESTROY (DB_ENV_ornull *env) |
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264 | CODE: |
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265 | if (env) |
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266 | env->close (env, 0); |
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267 | |
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268 | $int = $env->set_data_dir (const char *dir) |
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269 | $int = $env->set_tmp_dir (const char *dir) |
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270 | $int = $env->set_lg_dir (const char *dir) |
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271 | $int = $env->set_shm_key (long shm_key) |
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272 | $int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
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273 | $int = $env->set_flags (U32 flags, int onoff) |
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274 | $env->set_errfile (FILE *errfile = 0) |
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275 | $env->set_msgfile (FILE *msgfile = 0) |
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276 | $int = $env->set_verbose (U32 which, int onoff = 1) |
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277 | $int = $env->set_encrypt (const char *password, U32 flags = 0) |
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278 | $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
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279 | $int = $env->set_mp_max_openfd (int maxopenfd); |
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280 | $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); |
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281 | $int = $env->set_mp_mmapsize (int mmapsize_mb) |
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282 | $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) |
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283 | $int = $env->set_lk_max_lockers (U32 max) |
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284 | $int = $env->set_lk_max_locks (U32 max) |
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285 | $int = $env->set_lk_max_objects (U32 max) |
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286 | $int = $env->set_lg_bsize (U32 max) |
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287 | $int = $env->set_lg_max (U32 max) |
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288 | $int = $env->mutex_set_increment (U32 increment) |
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289 | $int = $env->mutex_set_tas_spins (U32 tas_spins) |
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290 | $int = $env->mutex_set_max (U32 max) |
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291 | $int = $env->mutex_set_align (U32 align) |
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292 | |
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293 | $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) |
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294 | flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC |
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295 | |
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296 | =head4 Example: |
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297 | |
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298 | use AnyEvent; |
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299 | use BDB; |
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300 | |
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301 | our $FH; open $FH, "<&=" . BDB::poll_fileno; |
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302 | our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb); |
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303 | |
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304 | BDB::min_parallel 8; |
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305 | |
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306 | my $env = db_env_create; |
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307 | |
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308 | mkdir "bdtest", 0700; |
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309 | db_env_open |
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310 | $env, |
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311 | "bdtest", |
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312 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
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313 | 0600; |
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314 | |
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315 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
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316 | |
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317 | |
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318 | =head3 DB/database methods |
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319 | |
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320 | Methods available on DB/$db handles: |
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321 | |
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322 | DESTROY (DB_ornull *db) |
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323 | CODE: |
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324 | if (db) |
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325 | { |
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326 | SV *env = (SV *)db->app_private; |
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327 | db->close (db, 0); |
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328 | SvREFCNT_dec (env); |
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329 | } |
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330 | |
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331 | $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) |
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332 | $int = $db->set_flags (U32 flags) |
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333 | flags: CHKSUM ENCRYPT TXN_NOT_DURABLE |
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334 | Btree: DUP DUPSORT RECNUM REVSPLITOFF |
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335 | Hash: DUP DUPSORT |
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336 | Queue: INORDER |
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337 | Recno: RENUMBER SNAPSHOT |
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338 | |
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339 | $int = $db->set_encrypt (const char *password, U32 flags) |
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340 | $int = $db->set_lorder (int lorder) |
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341 | $int = $db->set_bt_minkey (U32 minkey) |
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342 | $int = $db->set_re_delim (int delim) |
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343 | $int = $db->set_re_pad (int re_pad) |
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344 | $int = $db->set_re_source (char *source) |
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345 | $int = $db->set_re_len (U32 re_len) |
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346 | $int = $db->set_h_ffactor (U32 h_ffactor) |
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347 | $int = $db->set_h_nelem (U32 h_nelem) |
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348 | $int = $db->set_q_extentsize (U32 extentsize) |
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349 | |
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350 | $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) |
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351 | flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT |
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352 | $seq = $db->sequence (U32 flags = 0) |
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353 | |
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354 | =head4 Example: |
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355 | |
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356 | my $db = db_create $env; |
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357 | db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; |
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358 | |
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359 | for (1..1000) { |
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360 | db_put $db, undef, "key $_", "data $_"; |
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361 | |
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362 | db_key_range $db, undef, "key $_", my $keyrange; |
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363 | my ($lt, $eq, $gt) = @$keyrange; |
|
|
364 | } |
|
|
365 | |
|
|
366 | db_del $db, undef, "key $_" for 1..1000; |
|
|
367 | |
|
|
368 | db_sync $db; |
|
|
369 | |
|
|
370 | |
|
|
371 | =head3 DB_TXN/transaction methods |
|
|
372 | |
|
|
373 | Methods available on DB_TXN/$txn handles: |
|
|
374 | |
|
|
375 | DESTROY (DB_TXN_ornull *txn) |
|
|
376 | CODE: |
|
|
377 | if (txn) |
|
|
378 | txn->abort (txn); |
|
|
379 | |
|
|
380 | $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT) |
|
|
381 | flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT |
|
|
382 | |
|
|
383 | $bool = $txn->failed |
|
|
384 | # see db_txn_finish documentation, above |
|
|
385 | |
|
|
386 | |
|
|
387 | =head3 DBC/cursor methods |
|
|
388 | |
|
|
389 | Methods available on DBC/$dbc handles: |
|
|
390 | |
|
|
391 | DESTROY (DBC_ornull *dbc) |
|
|
392 | CODE: |
|
|
393 | if (dbc) |
|
|
394 | dbc->c_close (dbc); |
|
|
395 | |
|
|
396 | $int = $cursor->set_priority ($priority = PRIORITY_*) |
|
|
397 | |
|
|
398 | =head4 Example: |
|
|
399 | |
|
|
400 | my $c = $db->cursor; |
|
|
401 | |
|
|
402 | for (;;) { |
|
|
403 | db_c_get $c, my $key, my $data, BDB::NEXT; |
|
|
404 | warn "<$!,$key,$data>"; |
|
|
405 | last if $!; |
|
|
406 | } |
|
|
407 | |
|
|
408 | db_c_close $c; |
|
|
409 | |
|
|
410 | |
|
|
411 | =head3 DB_SEQUENCE/sequence methods |
|
|
412 | |
|
|
413 | Methods available on DB_SEQUENCE/$seq handles: |
|
|
414 | |
|
|
415 | DESTROY (DB_SEQUENCE_ornull *seq) |
|
|
416 | CODE: |
|
|
417 | if (seq) |
|
|
418 | seq->close (seq, 0); |
|
|
419 | |
|
|
420 | $int = $seq->initial_value (db_seq_t value) |
|
|
421 | $int = $seq->set_cachesize (U32 size) |
|
|
422 | $int = $seq->set_flags (U32 flags) |
|
|
423 | flags: SEQ_DEC SEQ_INC SEQ_WRAP |
|
|
424 | $int = $seq->set_range (db_seq_t min, db_seq_t max) |
|
|
425 | |
|
|
426 | =head4 Example: |
|
|
427 | |
|
|
428 | my $seq = $db->sequence; |
|
|
429 | |
|
|
430 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
|
|
431 | db_sequence_get $seq, undef, 1, my $value; |
|
|
432 | |
|
|
433 | |
80 | =head2 SUPPORT FUNCTIONS |
434 | =head2 SUPPORT FUNCTIONS |
81 | |
435 | |
82 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
436 | =head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
83 | |
437 | |
84 | =over 4 |
438 | =over 4 |
85 | |
439 | |
|
|
440 | =item $msg = BDB::strerror [$errno] |
|
|
441 | |
|
|
442 | Returns the string corresponding to the given errno value. If no argument |
|
|
443 | is given, use C<$!>. |
|
|
444 | |
86 | =item $fileno = BDB::AIO::poll_fileno |
445 | =item $fileno = BDB::poll_fileno |
87 | |
446 | |
88 | Return the I<request result pipe file descriptor>. This filehandle must be |
447 | Return the I<request result pipe file descriptor>. This filehandle must be |
89 | polled for reading by some mechanism outside this module (e.g. Event or |
448 | polled for reading by some mechanism outside this module (e.g. Event or |
90 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
449 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
91 | to call C<poll_cb> to check the results. |
450 | to call C<poll_cb> to check the results. |
92 | |
451 | |
93 | See C<poll_cb> for an example. |
452 | See C<poll_cb> for an example. |
94 | |
453 | |
95 | =item BDB::AIO::poll_cb |
454 | =item BDB::poll_cb |
96 | |
455 | |
97 | Process some outstanding events on the result pipe. You have to call this |
456 | Process some outstanding events on the result pipe. You have to call this |
98 | regularly. Returns the number of events processed. Returns immediately |
457 | regularly. Returns the number of events processed. Returns immediately |
99 | when no events are outstanding. The amount of events processed depends on |
458 | when no events are outstanding. The amount of events processed depends on |
100 | the settings of C<BDB::AIO::max_poll_req> and C<BDB::AIO::max_poll_time>. |
459 | the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>. |
101 | |
460 | |
102 | If not all requests were processed for whatever reason, the filehandle |
461 | If not all requests were processed for whatever reason, the filehandle |
103 | will still be ready when C<poll_cb> returns. |
462 | will still be ready when C<poll_cb> returns. |
104 | |
463 | |
105 | Example: Install an Event watcher that automatically calls |
464 | Example: Install an Event watcher that automatically calls |
106 | BDB::AIO::poll_cb with high priority: |
465 | BDB::poll_cb with high priority: |
107 | |
466 | |
108 | Event->io (fd => BDB::AIO::poll_fileno, |
467 | Event->io (fd => BDB::poll_fileno, |
109 | poll => 'r', async => 1, |
468 | poll => 'r', async => 1, |
110 | cb => \&BDB::AIO::poll_cb); |
469 | cb => \&BDB::poll_cb); |
111 | |
470 | |
112 | =item BDB::AIO::max_poll_reqs $nreqs |
471 | =item BDB::max_poll_reqs $nreqs |
113 | |
472 | |
114 | =item BDB::AIO::max_poll_time $seconds |
473 | =item BDB::max_poll_time $seconds |
115 | |
474 | |
116 | These set the maximum number of requests (default C<0>, meaning infinity) |
475 | These set the maximum number of requests (default C<0>, meaning infinity) |
117 | that are being processed by C<BDB::AIO::poll_cb> in one call, respectively |
476 | that are being processed by C<BDB::poll_cb> in one call, respectively |
118 | the maximum amount of time (default C<0>, meaning infinity) spent in |
477 | the maximum amount of time (default C<0>, meaning infinity) spent in |
119 | C<BDB::AIO::poll_cb> to process requests (more correctly the mininum amount |
478 | C<BDB::poll_cb> to process requests (more correctly the mininum amount |
120 | of time C<poll_cb> is allowed to use). |
479 | of time C<poll_cb> is allowed to use). |
121 | |
480 | |
122 | Setting C<max_poll_time> to a non-zero value creates an overhead of one |
481 | Setting C<max_poll_time> to a non-zero value creates an overhead of one |
123 | syscall per request processed, which is not normally a problem unless your |
482 | syscall per request processed, which is not normally a problem unless your |
124 | callbacks are really really fast or your OS is really really slow (I am |
483 | callbacks are really really fast or your OS is really really slow (I am |
… | |
… | |
128 | interactiveness when perl is not fast enough to process all requests in |
487 | interactiveness when perl is not fast enough to process all requests in |
129 | time. |
488 | time. |
130 | |
489 | |
131 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
490 | For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
132 | |
491 | |
133 | Example: Install an Event watcher that automatically calls |
492 | Example: Install an EV watcher that automatically calls |
134 | BDB::AIO::poll_cb with low priority, to ensure that other parts of the |
493 | BDB::poll_cb with low priority, to ensure that other parts of the |
135 | program get the CPU sometimes even under high AIO load. |
494 | program get the CPU sometimes even under high load. |
136 | |
495 | |
137 | # try not to spend much more than 0.1s in poll_cb |
496 | # try not to spend much more than 0.1s in poll_cb |
138 | BDB::AIO::max_poll_time 0.1; |
497 | BDB::max_poll_time 0.1; |
139 | |
498 | |
140 | # use a low priority so other tasks have priority |
499 | my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb); |
141 | Event->io (fd => BDB::AIO::poll_fileno, |
|
|
142 | poll => 'r', nice => 1, |
|
|
143 | cb => &BDB::AIO::poll_cb); |
|
|
144 | |
500 | |
145 | =item BDB::AIO::poll_wait |
501 | =item BDB::poll_wait |
146 | |
502 | |
147 | If there are any outstanding requests and none of them in the result |
503 | If there are any outstanding requests and none of them in the result |
148 | phase, wait till the result filehandle becomes ready for reading (simply |
504 | phase, wait till the result filehandle becomes ready for reading (simply |
149 | does a C<select> on the filehandle. This is useful if you want to |
505 | does a C<select> on the filehandle. This is useful if you want to |
150 | synchronously wait for some requests to finish). |
506 | synchronously wait for some requests to finish). |
151 | |
507 | |
152 | See C<nreqs> for an example. |
508 | See C<nreqs> for an example. |
153 | |
509 | |
154 | =item BDB::AIO::poll |
510 | =item BDB::poll |
155 | |
511 | |
156 | Waits until some requests have been handled. |
512 | Waits until some requests have been handled. |
157 | |
513 | |
158 | Returns the number of requests processed, but is otherwise strictly |
514 | Returns the number of requests processed, but is otherwise strictly |
159 | equivalent to: |
515 | equivalent to: |
160 | |
516 | |
161 | BDB::AIO::poll_wait, BDB::AIO::poll_cb |
517 | BDB::poll_wait, BDB::poll_cb |
162 | |
518 | |
163 | =item BDB::AIO::flush |
519 | =item BDB::flush |
164 | |
520 | |
165 | Wait till all outstanding AIO requests have been handled. |
521 | Wait till all outstanding BDB requests have been handled. |
166 | |
522 | |
167 | Strictly equivalent to: |
523 | Strictly equivalent to: |
168 | |
524 | |
169 | BDB::AIO::poll_wait, BDB::AIO::poll_cb |
525 | BDB::poll_wait, BDB::poll_cb |
170 | while BDB::AIO::nreqs; |
526 | while BDB::nreqs; |
|
|
527 | |
|
|
528 | =back |
171 | |
529 | |
172 | =head3 CONTROLLING THE NUMBER OF THREADS |
530 | =head3 CONTROLLING THE NUMBER OF THREADS |
173 | |
531 | |
|
|
532 | =over 4 |
|
|
533 | |
174 | =item BDB::AIO::min_parallel $nthreads |
534 | =item BDB::min_parallel $nthreads |
175 | |
535 | |
176 | Set the minimum number of AIO threads to C<$nthreads>. The current |
536 | Set the minimum number of BDB threads to C<$nthreads>. The current |
177 | default is C<8>, which means eight asynchronous operations can execute |
537 | default is C<8>, which means eight asynchronous operations can execute |
178 | concurrently at any one time (the number of outstanding requests, |
538 | concurrently at any one time (the number of outstanding requests, |
179 | however, is unlimited). |
539 | however, is unlimited). |
180 | |
540 | |
181 | BDB::AIO starts threads only on demand, when an AIO request is queued and |
541 | BDB starts threads only on demand, when an BDB request is queued and |
182 | no free thread exists. Please note that queueing up a hundred requests can |
542 | no free thread exists. Please note that queueing up a hundred requests can |
183 | create demand for a hundred threads, even if it turns out that everything |
543 | create demand for a hundred threads, even if it turns out that everything |
184 | is in the cache and could have been processed faster by a single thread. |
544 | is in the cache and could have been processed faster by a single thread. |
185 | |
545 | |
186 | It is recommended to keep the number of threads relatively low, as some |
546 | It is recommended to keep the number of threads relatively low, as some |
… | |
… | |
189 | versions, 4-32 threads should be fine. |
549 | versions, 4-32 threads should be fine. |
190 | |
550 | |
191 | Under most circumstances you don't need to call this function, as the |
551 | Under most circumstances you don't need to call this function, as the |
192 | module selects a default that is suitable for low to moderate load. |
552 | module selects a default that is suitable for low to moderate load. |
193 | |
553 | |
194 | =item BDB::AIO::max_parallel $nthreads |
554 | =item BDB::max_parallel $nthreads |
195 | |
555 | |
196 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
556 | Sets the maximum number of BDB threads to C<$nthreads>. If more than the |
197 | specified number of threads are currently running, this function kills |
557 | specified number of threads are currently running, this function kills |
198 | them. This function blocks until the limit is reached. |
558 | them. This function blocks until the limit is reached. |
199 | |
559 | |
200 | While C<$nthreads> are zero, aio requests get queued but not executed |
560 | While C<$nthreads> are zero, aio requests get queued but not executed |
201 | until the number of threads has been increased again. |
561 | until the number of threads has been increased again. |
… | |
… | |
203 | This module automatically runs C<max_parallel 0> at program end, to ensure |
563 | This module automatically runs C<max_parallel 0> at program end, to ensure |
204 | that all threads are killed and that there are no outstanding requests. |
564 | that all threads are killed and that there are no outstanding requests. |
205 | |
565 | |
206 | Under normal circumstances you don't need to call this function. |
566 | Under normal circumstances you don't need to call this function. |
207 | |
567 | |
208 | =item BDB::AIO::max_idle $nthreads |
568 | =item BDB::max_idle $nthreads |
209 | |
569 | |
210 | Limit the number of threads (default: 4) that are allowed to idle (i.e., |
570 | Limit the number of threads (default: 4) that are allowed to idle (i.e., |
211 | threads that did not get a request to process within 10 seconds). That |
571 | threads that did not get a request to process within 10 seconds). That |
212 | means if a thread becomes idle while C<$nthreads> other threads are also |
572 | means if a thread becomes idle while C<$nthreads> other threads are also |
213 | idle, it will free its resources and exit. |
573 | idle, it will free its resources and exit. |
… | |
… | |
218 | |
578 | |
219 | The default is probably ok in most situations, especially if thread |
579 | The default is probably ok in most situations, especially if thread |
220 | creation is fast. If thread creation is very slow on your system you might |
580 | creation is fast. If thread creation is very slow on your system you might |
221 | want to use larger values. |
581 | want to use larger values. |
222 | |
582 | |
223 | =item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs |
583 | =item $oldmaxreqs = BDB::max_outstanding $maxreqs |
224 | |
584 | |
225 | This is a very bad function to use in interactive programs because it |
585 | This is a very bad function to use in interactive programs because it |
226 | blocks, and a bad way to reduce concurrency because it is inexact: Better |
586 | blocks, and a bad way to reduce concurrency because it is inexact: Better |
227 | use an C<aio_group> together with a feed callback. |
587 | use an C<aio_group> together with a feed callback. |
228 | |
588 | |
… | |
… | |
236 | |
596 | |
237 | You can still queue as many requests as you want. Therefore, |
597 | You can still queue as many requests as you want. Therefore, |
238 | C<max_oustsanding> is mainly useful in simple scripts (with low values) or |
598 | C<max_oustsanding> is mainly useful in simple scripts (with low values) or |
239 | as a stop gap to shield against fatal memory overflow (with large values). |
599 | as a stop gap to shield against fatal memory overflow (with large values). |
240 | |
600 | |
|
|
601 | =item BDB::set_sync_prepare $cb |
|
|
602 | |
|
|
603 | Sets a callback that is called whenever a request is created without an |
|
|
604 | explicit callback. It has to return two code references. The first is used |
|
|
605 | as the request callback, and the second is called to wait until the first |
|
|
606 | callback has been called. The default implementation works like this: |
|
|
607 | |
|
|
608 | sub { |
|
|
609 | my $status; |
|
|
610 | ( |
|
|
611 | sub { $status = $! }, |
|
|
612 | sub { BDB::poll while !defined $status; $! = $status }, |
|
|
613 | ) |
|
|
614 | } |
|
|
615 | |
|
|
616 | =back |
|
|
617 | |
241 | =head3 STATISTICAL INFORMATION |
618 | =head3 STATISTICAL INFORMATION |
242 | |
619 | |
|
|
620 | =over 4 |
|
|
621 | |
243 | =item BDB::AIO::nreqs |
622 | =item BDB::nreqs |
244 | |
623 | |
245 | Returns the number of requests currently in the ready, execute or pending |
624 | Returns the number of requests currently in the ready, execute or pending |
246 | states (i.e. for which their callback has not been invoked yet). |
625 | states (i.e. for which their callback has not been invoked yet). |
247 | |
626 | |
248 | Example: wait till there are no outstanding requests anymore: |
627 | Example: wait till there are no outstanding requests anymore: |
249 | |
628 | |
250 | BDB::AIO::poll_wait, BDB::AIO::poll_cb |
629 | BDB::poll_wait, BDB::poll_cb |
251 | while BDB::AIO::nreqs; |
630 | while BDB::nreqs; |
252 | |
631 | |
253 | =item BDB::AIO::nready |
632 | =item BDB::nready |
254 | |
633 | |
255 | Returns the number of requests currently in the ready state (not yet |
634 | Returns the number of requests currently in the ready state (not yet |
256 | executed). |
635 | executed). |
257 | |
636 | |
258 | =item BDB::AIO::npending |
637 | =item BDB::npending |
259 | |
638 | |
260 | Returns the number of requests currently in the pending state (executed, |
639 | Returns the number of requests currently in the pending state (executed, |
261 | but not yet processed by poll_cb). |
640 | but not yet processed by poll_cb). |
262 | |
641 | |
263 | =back |
642 | =back |
264 | |
643 | |
265 | =cut |
644 | =cut |
266 | |
645 | |
267 | # support function to convert a fd into a perl filehandle |
646 | set_sync_prepare { |
268 | sub _fd2fh { |
647 | my $status; |
269 | return undef if $_[0] < 0; |
648 | ( |
270 | |
649 | sub { |
271 | # try to generate nice filehandles |
650 | $status = $!; |
272 | my $sym = "BDB::AIO::fd#$_[0]"; |
651 | }, |
273 | local *$sym; |
652 | sub { |
274 | |
653 | BDB::poll while !defined $status; |
275 | open *$sym, "+<&=$_[0]" # usually works under any unix |
654 | $! = $status; |
276 | or open *$sym, "<&=$_[0]" # cygwin needs this |
655 | }, |
277 | or open *$sym, ">&=$_[0]" # or this |
656 | ) |
278 | or return undef; |
657 | }; |
279 | |
|
|
280 | *$sym |
|
|
281 | } |
|
|
282 | |
658 | |
283 | min_parallel 8; |
659 | min_parallel 8; |
284 | |
660 | |
285 | END { flush } |
661 | END { flush } |
286 | |
662 | |
… | |
… | |
288 | |
664 | |
289 | =head2 FORK BEHAVIOUR |
665 | =head2 FORK BEHAVIOUR |
290 | |
666 | |
291 | This module should do "the right thing" when the process using it forks: |
667 | This module should do "the right thing" when the process using it forks: |
292 | |
668 | |
293 | Before the fork, IO::AIO enters a quiescent state where no requests |
669 | Before the fork, BDB enters a quiescent state where no requests |
294 | can be added in other threads and no results will be processed. After |
670 | can be added in other threads and no results will be processed. After |
295 | the fork the parent simply leaves the quiescent state and continues |
671 | the fork the parent simply leaves the quiescent state and continues |
296 | request/result processing, while the child frees the request/result queue |
672 | request/result processing, while the child frees the request/result queue |
297 | (so that the requests started before the fork will only be handled in the |
673 | (so that the requests started before the fork will only be handled in the |
298 | parent). Threads will be started on demand until the limit set in the |
674 | parent). Threads will be started on demand until the limit set in the |
299 | parent process has been reached again. |
675 | parent process has been reached again. |
300 | |
676 | |
301 | In short: the parent will, after a short pause, continue as if fork had |
677 | In short: the parent will, after a short pause, continue as if fork had |
302 | not been called, while the child will act as if IO::AIO has not been used |
678 | not been called, while the child will act as if BDB has not been used |
303 | yet. |
679 | yet. |
|
|
680 | |
|
|
681 | Win32 note: there is no fork on win32, and perls emulation of it is too |
|
|
682 | broken to be supported, so do not use BDB in a windows pseudo-fork, better |
|
|
683 | yet, switch to a more capable platform. |
304 | |
684 | |
305 | =head2 MEMORY USAGE |
685 | =head2 MEMORY USAGE |
306 | |
686 | |
307 | Per-request usage: |
687 | Per-request usage: |
308 | |
688 | |
… | |
… | |
310 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
690 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
311 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
691 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
312 | scalars and other data passed into aio requests will also be locked and |
692 | scalars and other data passed into aio requests will also be locked and |
313 | will consume memory till the request has entered the done state. |
693 | will consume memory till the request has entered the done state. |
314 | |
694 | |
315 | This is now awfully much, so queuing lots of requests is not usually a |
695 | This is not awfully much, so queuing lots of requests is not usually a |
316 | problem. |
696 | problem. |
317 | |
697 | |
318 | Per-thread usage: |
698 | Per-thread usage: |
319 | |
699 | |
320 | In the execution phase, some aio requests require more memory for |
700 | In the execution phase, some aio requests require more memory for |
321 | temporary buffers, and each thread requires a stack and other data |
701 | temporary buffers, and each thread requires a stack and other data |
322 | structures (usually around 16k-128k, depending on the OS). |
702 | structures (usually around 16k-128k, depending on the OS). |
323 | |
703 | |
324 | =head1 KNOWN BUGS |
704 | =head1 KNOWN BUGS |
325 | |
705 | |
326 | Known bugs will be fixed in the next release. |
706 | Known bugs will be fixed in the next release, except: |
|
|
707 | |
|
|
708 | If you use a transaction in any request, and the request returns |
|
|
709 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
|
|
710 | TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, |
|
|
711 | above. |
327 | |
712 | |
328 | =head1 SEE ALSO |
713 | =head1 SEE ALSO |
329 | |
714 | |
330 | L<Coro::AIO>. |
715 | L<Coro::BDB>, L<IO::AIO>. |
331 | |
716 | |
332 | =head1 AUTHOR |
717 | =head1 AUTHOR |
333 | |
718 | |
334 | Marc Lehmann <schmorp@schmorp.de> |
719 | Marc Lehmann <schmorp@schmorp.de> |
335 | http://home.schmorp.de/ |
720 | http://home.schmorp.de/ |