[QUESTION] Are there more Limits in LiteDB than in the Docu?

[mahop-net]

Hello, I found the following Limits in the docu. Are there more Limits to care about? (And I have some questions)

LiteDB Limits found in Docs:

• Collections Names in Sum: 8000 B
• Classes Hierarchy Depth: Default max. 20
• Max Document Size: 1 MB or 16 MB ??? (after BSON Serialisation)
  • 16 MB https://www.litedb.org/docs/bsondocument/
  • 1 MB https://www.litedb.org/docs/filestorage/ - Which is correct?
• Max Index Value Size: 1024 B (after BSON Serialisation)
  • Up to 255 indexes per collections, including the _id primary key, but limited to 8096 bytes for index definition.
  • Each index uses: 41 bytes + LEN(name) + LEN(expression) - So if you have a two letter name for each index the maximum index count is 188
• Max Primary Key Value Size: 1024 B (after BSON Serialisation)
• Max File ID: 1024 B (after BSON Serialisation) ??? Probably - Because this is a index ???

Are there more Limits?

• Max FileSize in File Storage?
• Max Database Size?
• Max Memory Usage? (Is Setting available?)

Questions:

• In the Limits - How much space takes one Char in Bytes? E.g.: Are Collection Names stored in UTF8 or ASCII?

And (Two more things):

• How does LiteDB Cache work? Is it faster to keep a Connection Open for Multiple queries?
• What is db.Checkpoint() doing? Do I have to call it from Time to Time?

Thanks a lot for your great work!!! LiteDB looks cool, I would like to use it in a new project.... Nice greeting from Bavaria, Markus

[ProKn1fe]

I found only database size limit and it can be changed as LiteDatabase.LimitSize. Also i don't think there is any file size limit but i recommend to not store many large files.

[mahop-net]

So finally I scanned the code and got some Limits:

• Limit of Database is the Limit of the Disk (Can be set to a Maximum in Code as mentioned by @ProKn1fe )
  • Make sure you have a 64bit app. Otherwise you will hit Momory limits really soon
  • Select count(*) from X is running into an "Out of Memory Exception" already on a Collection with around 50 Mio small Records) in case of 32 Bit (Tested with LiteDB.Studio witch is complied with 32 Bit in the downloadable version here on Github)
• Max Document Size: Around 16 MB (After BSON Conversion and with UTF8 Encoding)
  • Actually 15,910 MB (See Constants.MAX_DOCUMENT_SIZE)
• Max Index Name Length: 32 B (See Constants.INDEX_NAME_MAX_LENGTH)
• Max Index Key Length: 1023 B (See Constants.MAX_INDEX_KEY_LENGTH)
  • Max Primary Key Value Size: 1023 B (after BSON Serialisation)
  • Max File ID: 1023 B (after BSON Serialisation)
• Max OpenTransactions: 100 (See Constants.MAX_OPEN_TRANSACTIONS)
  • All Transactions can consume around 1GB of RAM before written to Disk
• Collections Names in Sum: 8000 B (UTF8 Encoded)
• Classes Hierarchy Depth: Default max. 20 (Can be raised)
• Up to 255 indexes per collections, including the _id primary key, but limited to 8096 bytes for index definition.
  • Each index uses: 41 bytes + LEN(name) + LEN(expression)
  • So if you have a two letter name for each index the maximum index count is 188

I did not find a Limit for FileSize stored in the FileStorage

[mahop-net]

And about the two qestions:

How does LiteDB Cache work? Is it faster to keep a Connection Open for Multiple queries?

• The Chache is per db Instance. So if you dispose the db Instance the caching restarts.

What is db.Checkpoint() doing? Do I have to call it from time to time?

• It is writing the Log to the database file. So I think it has to be called only, if you have a long living db instance... (But this is not for sure... so this question is still open)