90 lines
2.7 KiB
Nim
90 lines
2.7 KiB
Nim
import ../rocksdb/lib/librocksdb, cpuinfo
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const
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dbPath: cstring = "/tmp/rocksdb_simple_example"
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dbBackupPath: cstring = "/tmp/rocksdb_simple_example_backup"
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proc main() =
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var
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db: ptr rocksdb_t
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be: ptr rocksdb_backup_engine_t
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options = rocksdb_options_create()
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# Optimize RocksDB. This is the easiest way to
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# get RocksDB to perform well
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let cpus = countProcessors()
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rocksdb_options_increase_parallelism(options, cpus.int32)
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# This requires snappy - disabled because rocksdb is not always compiled with
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# snappy support (for example Fedora 28, certain Ubuntu versions)
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# rocksdb_options_optimize_level_style_compaction(options, 0);
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# create the DB if it's not already present
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rocksdb_options_set_create_if_missing(options, 1)
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var # open DB
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err: cstring # memory leak: example code does not free error string!
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db = rocksdb_open(options, dbPath, cast[cstringArray](err.addr))
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doAssert err.isNil, $err
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# open Backup Engine that we will use for backing up our database
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be = rocksdb_backup_engine_open(options, dbBackupPath, cast[cstringArray](err.addr))
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doAssert err.isNil, $err
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# Put key-value
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var writeOptions = rocksdb_writeoptions_create()
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let key = "key"
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let put_value = "value"
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rocksdb_put(
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db,
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writeOptions,
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key.cstring,
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key.len.csize_t,
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put_value.cstring,
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put_value.len.csize_t,
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cast[cstringArray](err.addr),
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)
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doAssert err.isNil, $err
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# Get value
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var readOptions = rocksdb_readoptions_create()
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var len: csize_t
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let raw_value = rocksdb_get(
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db,
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readOptions,
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key.cstring,
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key.len.csize_t,
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addr len,
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cast[cstringArray](err.addr),
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) # Important: rocksdb_get is not null-terminated
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doAssert err.isNil, $err
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# Copy it to a regular Nim string (copyMem workaround because raw value is NOT null-terminated)
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var get_value = newString(len.int)
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copyMem(addr get_value[0], unsafeAddr raw_value[0], len.int * sizeof(char))
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doAssert get_value == put_value
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# create new backup in a directory specified by DBBackupPath
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rocksdb_backup_engine_create_new_backup(be, db, cast[cstringArray](err.addr))
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doAssert err.isNil, $err
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rocksdb_close(db)
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# If something is wrong, you might want to restore data from last backup
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var restoreOptions = rocksdb_restore_options_create()
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rocksdb_backup_engine_restore_db_from_latest_backup(
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be, dbPath, dbPath, restoreOptions, cast[cstringArray](err.addr)
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)
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doAssert err.isNil, $err
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rocksdb_restore_options_destroy(restore_options)
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db = rocksdb_open(options, dbPath, cast[cstringArray](err.addr))
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doAssert err.isNil, $err
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# cleanup
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rocksdb_writeoptions_destroy(writeOptions)
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rocksdb_readoptions_destroy(readOptions)
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rocksdb_options_destroy(options)
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rocksdb_backup_engine_close(be)
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rocksdb_close(db)
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main()
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