MapDB provides concurrent Maps, Sets and Queues backed by disk storage or off-heap-memory. It is a fast and easy to use embedded Java database engine.
HI
I am using mapdb v3.0.8
how to reclaim the file size ?
list is empty，but file is too largelocalDB = DBMaker.fileDB(DB_FILE_PATH) .fileMmapEnable() .checksumHeaderBypass() .make(); IndexTreeList<T> list = localDB.indexTreeList(DB_FILE_EVENT, new ObjectSerializer<T>()).createOrOpen();
I believe you can call list.getStore().compact()
sun.misc and sun.nio.ch in its manifest. I've found a workaround here https://search.maven.org/artifact/net.sdruskat/net.sdruskat.fragment.sun.misc/1.0.0/jar to expose sun.misc to OSGi. But unfortunately I haven't found something similar for the sun.nio.ch package. I've tried creating this kind of fragment myself, but I haven't been that successful so far. I would also like to avoid to upgrade to mapDBv3 since I'm not sure if there are any compatability issues with the source code, and I'd also have to get kotlin running in an eclipse developing environment and within the tycho maven build.Any advice on getting
sun.nio.ch exposed to OSGi / the tycho build?
Method name '%%%verify$mapdb' in class 'org.mapdb.DB$Maker' cannot be represented in dex format. build error message. I saw this happen before, I'm wondering if there are any progresses on this problem?
NavigableSet. tailSet with inclusive 'false' including the equal value in the result set
https://mapdb.org/blog/mapdb_in_february_2021/
@jankotek QUES on the hashmap or treemap with nested data structure. With the following code block:
HTreeMap<String, List<String>> map = (HTreeMap<String, List<String>>) DBMaker.fileDB("map").make().hashMap("map").createOrOpen();
for (int i = 0; i< 10; i++) {
final int finalI = i;
for (int j = 0; j< 10; j++) {
final int finalJ = j;
map.compute(String.valueOf(finalI), (key, value) -> {
if (value == null) {
value = new ArrayList<>();
}
value.add(String.format("%d_%d", finalI, finalJ));
return value;
});
}
}It falls into deadloop. Instead, I need to copy the value and then return the modified new copy to make it work.
HTreeMap<String, List<String>> map = (HTreeMap<String, List<String>>) DBMaker.fileDB("map").make().hashMap("map").createOrOpen();
for (int i = 0; i< 10; i++) {
final int finalI = i;
for (int j = 0; j< 10; j++) {
final int finalJ = j;
map.compute(String.valueOf(finalI), (key, value) -> {
final List<String> newValue;
if (value == null) {
newValue = new ArrayList<>();
} else {
newValue = new ArrayList<>(value);
}
newValue.add(String.format("%d_%d", finalI, finalJ));
return newValue;
});
}
}Is it a bug or it is expected? I think this is not an issue with in-memory counterpart (e.g. concurrentHashMap)
1 reply
Hi, Another question on how expire works in MapDB. The following snippet does not work
@Test
public void testExpiration() throws InterruptedException {
HTreeMap<String, String> map = (HTreeMap<String, String>) DBMaker
// .fileDB("map").fileDeleteAfterClose()
.memoryDB()
.make().hashMap("map")
.expireAfterCreate(10)
.createOrOpen();
map.put("a", "b");
Thread.sleep(4000);
assertNull(map.get("a"));
map.close();
}Did I misunderstand how expiration works?
I want to use SortedTableMap i have ip as key and want multiple values in value section as columns in tables is there any way to achieve it using it ?Tried from examples given but not able to do so if anyone can help on it..
Thnx
This is sample data that i want to feed
3754892057--this is ip hashcode generated
THis are all values -- "PUB","TH","Thailand","Chon Buri","Ban Talat Bueng","Triple T Internet PCL","triplet.co.th","ISP","45629","JasTel Network International Gateway","30","-"
Hi, is it supported to store multiple HashMaps in one database? Something like:
DB db = DBMaker.fileDB("/tmp/test").closeOnJvmShutdown().make();
HTreeMap<byte[], MyClass> mapDB1 = db.hashMap("map")..keySerializer(Serializer.BYTE_ARRAY).valueSerializer(SERIALIZER.JAVA).createOrOpen();
HTreeMap<String, Integer> mapDB2 = db.hashMap("info")..keySerializer(Serializer.STRING).valueSerializer(SERIALIZER.INTEGER).createOrOpen();
MyClass c = new MyClass();
byte[] b = { 1, 2, 3, 4 };
mapDB1.put(b, c);
mapDB2.put("version", 1);
db.commit();
db.close();
I tried this and it worked in a very simple test but I want to be sure this is actually supported. Thank you!
Hey, quick question.
On 3.0.8., other than opening and closing a file based DB, is there a (static?) way to check the validity of a DB (properly closed, file corruption, what not).
MapDB files are relatively small and the use case is, i have to keep rather large source data files they are built on, but if i can verify that sources are no longer required i could release them (which could lead to them being deleted).
So is there away to do that in a oneliner, if not is DBMaker.make() enough to verify validity or do i have to open all required collections also?
Thanks.