add secondary index for existing data store(json).

2757632

i want to store json messages using BDB. we use json object property as a key and rest of the json object(bytes) as a data. later if we want to add secondary index  targeting  json object property for existing data store, i can't do that because data is remain as a bytes.is their any recommend way to do that.i'm very new to BDB.

Greybird-Oracle

In BDB, the field used for a secondary index is extracted from the primary record's data (the byte[]) using code that you write.  So you can convert the primary record's data bytes to JSON, pull out the property you want, and then convert that property to bytes (since all BDB keys are bytes as well).

See:

SecondaryKeyCreator (Oracle - Berkeley DB Java Edition API)

And to make it easy to convert the property to bytes:

com.sleepycat.bind.tuple (Oracle - Berkeley DB Java Edition API)

The collections API tutorial is good for learning how this all works, even if you're not using the collections API:

Berkeley DB Java Edition Collections Tutorial

--mark

Greybird-Oracle

In BDB, the field used for a secondary index is extracted from the primary record's data (the byte[]) using code that you write.  So you can convert the primary record's data bytes to JSON, pull out the property you want, and then convert that property to bytes (since all BDB keys are bytes as well).

See:

SecondaryKeyCreator (Oracle - Berkeley DB Java Edition API)

And to make it easy to convert the property to bytes:

com.sleepycat.bind.tuple (Oracle - Berkeley DB Java Edition API)

The collections API tutorial is good for learning how this all works, even if you're not using the collections API:

Berkeley DB Java Edition Collections Tutorial

--mark

2757632

i just tries that secondary key creation  option.so createSecondaryKey call when index creation ,but first key is one of sequence name that i use to auto generate primary key for data store.afterwords records seems correct.

i have using setAllowPopulate(true) config with secondary index.

Greybird-Oracle

Good, glad to hear you got it working.

Also be sure to see the information at the top of this class:

SecondaryDatabase (Oracle - Berkeley DB Java Edition API)

--mark

2757632

thank you for the all the information mark.  i realize that sequence is also kept as a record in primary database.

is there any easy way to skip sequence record from primary database other than remembering sequence name ad skip all records if key is one of sequence name. because i want to  extract only json object from primary database.

Greybird-Oracle

If you put your sequence record in the primary DB, there is no other way to handle it except to recognize it and ignore it in your SecondaryKeyCreator.

I recommend that sequence records are stored in a separate DB, just for sequences and perhaps other metadata.  This is cleaner, because none of your code that processes the primary records will have to be aware of the sequence record.

--mark