| java.lang.Object
 com.sleepycat.je.util.DbCacheSize
| DbCacheSize | | public class DbCacheSize (Code) | | Estimating JE in-memory sizes as a function of key and data size is not
straightforward for two reasons. There is some fixed overhead for each btree
internal node, so tree fanout and degree of node sparseness impacts memory
consumption. In addition, JE compresses some of the internal nodes where
possible, but compression depends on on-disk layouts.
DbCacheSize is an aid for estimating cache sizes. To get an estimate of the
in-memory footprint for a given database, specify the number of records and
record characteristics and DbCacheSize will return a minimum and maximum
estimate of the cache size required for holding the database in memory.
If the user specifies the record's data size, the utility will return both
values for holding just the internal nodes of the btree, and for holding the
entire database in cache.
Note that "cache size" is a percentage more than "btree size", to cover
general environment resources like log buffers. Each invocation of the
utility returns an estimate for a single database in an environment. For an
environment with multiple databases, run the utility for each database, add
up the btree sizes, and then add 10 percent.
Note that the utility does not yet cover duplicate records and the API is
subject to change release to release.
The only required parameters are the number of records and key size.
Data size, non-tree cache overhead, btree fanout, and other parameters
can also be provided. For example:
$ java DbCacheSize -records 554719 -key 16 -data 100
Inputs: records=554719 keySize=16 dataSize=100 nodeMax=128 density=80%
overhead=10%
Cache Size Btree Size Description
-------------- -------------- -----------
30,547,440 27,492,696 Minimum, internal nodes only
41,460,720 37,314,648 Maximum, internal nodes only
114,371,644 102,934,480 Minimum, internal nodes and leaf nodes
125,284,924 112,756,432 Maximum, internal nodes and leaf nodes
Btree levels: 3
This says that the minimum cache size to hold only the internal nodes of the
btree in cache is approximately 30MB. The maximum size to hold the entire
database in cache, both internal nodes and datarecords, is 125Mb.
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| Constructor Summary | |
| public | DbCacheSize(long records, int keySize, int dataSize, int nodeMax, int density, long overhead)
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| DbCacheSize | | public DbCacheSize(long records, int keySize, int dataSize, int nodeMax, int density, long overhead)(Code) | | |
| getMaxBtreeSizeInternalNodesOnly | | public long getMaxBtreeSizeInternalNodesOnly()(Code) | | |
| getMaxBtreeSizeWithData | | public long getMaxBtreeSizeWithData()(Code) | | |
| getMaxCacheSizeInternalNodesOnly | | public long getMaxCacheSizeInternalNodesOnly()(Code) | | |
| getMaxCacheSizeWithData | | public long getMaxCacheSizeWithData()(Code) | | |
| getMinBtreeSizeInternalNodesOnly | | public long getMinBtreeSizeInternalNodesOnly()(Code) | | |
| getMinBtreeSizeWithData | | public long getMinBtreeSizeWithData()(Code) | | |
| getMinCacheSizeInternalNodesOnly | | public long getMinCacheSizeInternalNodesOnly()(Code) | | |
| getMinCacheSizeWithData | | public long getMinCacheSizeWithData()(Code) | | |
| getNLevels | | public int getNLevels()(Code) | | |
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