getPersistenceMeta
Syntax
getPersistenceMeta(table)
Arguments
table is a table object.
Details
Return metadata of a shared stream table that has been enabled to be persisted to disk.
Return a dictionary with the following keys:
sizeInMemory: the number of records in memory.
asynWrite: whether to persist data with asynchronous mode.
totalSize: the total number of records in the stream table.
compress: whether to save compressed data.
memoryOffset: the offset position of the first message in memory relative to all records in the stream table. memoryOffset = totalSize - sizeInMemory.
sizeOnDisk: the number of records that have been persisted to disk.
retentionMinutes: how long (in terms of minutes) the log file will be kept. The default value is 1440 minutes (1 day).
persistenceDir: the path to the persistent data.
hashValue: the identifier of the thread responsible for persisting the table to disk. If persistenceWorkerNum>1, hashValue may not be 0.
diskOffset: the offset position of the first message on disk relative to all records in the stream table.
Examples
$ colName=["time","x"]
$ colType=["timestamp","int"]
$ t = streamTable(100:0, colName, colType);
$ enableTableShareAndPersistence(table=t, tableName=`st, cacheSize=1200000)
$
$ go;
$
$ for(s in 0:200){
$ n=10000
$ time=2019.01.01T00:00:00.000+s*n+1..n
$ x=rand(10.0, n)
$ insert into st values(time, x)
$ }
$
$ getPersistenceMeta(st);
astLogSeqNum->-1
sizeInMemory->800000
asynWrite->true
totalSize->2000000
raftGroup->-1
compress->true
memoryOffset->1200000
retentionMinutes->1440
sizeOnDisk->2000000
persistenceDir->/dolphindb/server/streamPersistDir/st
hashValue->0
diskOffset->0