Block Metadata

Block metadata is stored, like all other information in Fluree, in the form of flakes. A block's hash, the previous block's hash, the signature for a transaction, and more is stored in metadata flakes that are automatically generated for every block.

Every block has one _block subject. This set of flakes is always processed last and has the lowest t.

In our example from the previous lesson, the below flakes from block 2 should have 3 additional subjects with ids -9, -10, and -11.

Subject	Predicate	Object	Time	Operation
12345	Hair Color	Red	-9	true
12345	Birthday	1/30/85	-9	true
12345	Fav Nums	7	-10	true
12345	Full Name	Jane Doe	-10	true
12345	Fav Nums	28	-10	true

-9 and -10 correspond to the ts of the flakes, and are _tx subjects. -11 does not correspond to the t of the flakes below, rather it is the id for a _block subject. (There are additional meta-data flakes that are added, below is just a sample). You can issue the query { "select": ["*"], "from": -9 } to see metadata subjects, just like you can look up all other subjects (some meta-data flakes are not searchable, but are recorded in the actual block files).

Subject	Predicate	Object	Time	Operation
12345	Hair Color	Red	-9	true
12345	Birthday	1/30/85	-9	true
12345	Fav Nums	7	-10	true
12345	Full Name	Jane Doe	-10	true
12345	Fav Nums	28	-10	true
-9	sig	Signature of the original JSON command	-9	true
-9	tx	[{ Original JSON transaction }]	-9	true
-9	auth	3425 (auth id that issued this transaction)	-9	true
-10	sig	Signature of the original JSON command	-10	true
-10	tx	[{ Original JSON transaction }]	-10	true
-10	auth	3425 (auth id that issued this transaction)	-10	true
-11	number	2 (this is the block number)	-11	true
-11	hash	SHA-256 hash for block	-11	true
-11	prevHash	Previous block's hash	-11	true
-11	transactions	[ -9, -10 ] (reference to the transactions in this block)	-11	true
-11	instant	Instant (time) when this block was created	-11	true