This is somewhat unlikely, but if a term is (incredibly) popular, its
uvarint count value representation might go beyond 8 bytes.
Some KVStore implementations (like forestdb) provide a BatchEx cgo
optimization that depends on proper preallocated counting, so this
change provides a proper worst-case estimate based on the max-unvarint
of 10 bytes instead of the previously incorrect 8 bytes.
With this change, the upside_down batchRows() and firestorm
batchRows() now use the new KVWriter.NewBatchEx() API, which can
improve performance by reducing the number of cgo hops.
In order to spend less time in append(), this change in upside_down
(similar to another recent performance change in firestorm) builds up
an array of arrays as the eventual input to batchRows().
Previously, the code would gather all the backIndexRows before
processing them. This change instead merges the backIndexRows
concurrently on the theory that we might as well make progress on
compute & processing tasks while waiting for the rest of the back
index rows to be fetched from the KVStore.
Start backindex reading concurrently with analysi to try to utilize
more I/O bandwidth.
The analysis time vs indexing time stats tracking are also now "off",
since there's now concurrency between those actiivties.
One tradeoff is that the lock area in upside_down Batch() is increased
as part of this change.
Taking another optimization from firestorm, upside_down's
storeField()/indexField() funcs now also append() to passed-in arrays
rather than always allocating their own arrays.
It boils down to:
1. client sends some work and a notification channel to a single worker,
then waits.
2. worker processes the work
3. worker sends the result to the client using the notification channel
I do not see any problem with this, even with unbuffered channels.
this lays the foundation for supporting the new firestorm
indexing scheme. i'm merging these changes ahead of
the rest of the firestorm branch so i can continue
to make changes to the analysis pipeline in parallel
in some limited cases we can detect unsafe usage
in these cases, do not trip over ourselves and panic
instead return a strongly typed error upside_down.UnsafeBatchUseDetected
also, introduced Batch.Reset() to allow batch reuse
this is currently still experimental
closes#195
refactor to share code in emulated batch
refactor to share code in emulated merge
refactor index kvstore benchmarks to share more code
refactor index kvstore benchmarks to be more repeatable
this introduces disk format v4
now the summary rows for a term are stored in their own
"dictionary row" format, previously the same information
was stored in special term frequency rows
this now allows us to easily iterate all the terms for a field
in sorted order (useful for many other fuzzy data structures)
at the top-level of bleve you can now browse terms within a field
using the following api on the Index interface:
FieldDict(field string) (index.FieldDict, error)
FieldDictRange(field string, startTerm []byte, endTerm []byte) (index.FieldDict, error)
FieldDictPrefix(field string, termPrefix []byte) (index.FieldDict, error)
fixes#127
