nimbus-eth1/nimbus/db/kvt/kvt_delta/delta_merge.nim
Jordan Hrycaj 5ac362fe6f
Aristo and kvt balancer management update (#2504)
* Aristo: Merge `delta_siblings` module into `deltaPersistent()`

* Aristo: Add `isEmpty()` for canonical checking whether a layer is empty

* Aristo: Merge `LayerDeltaRef` into `LayerObj`

why:
  No need to maintain nested object refs anymore. Previously the
 `LayerDeltaRef` object had a companion `LayerFinalRef` which held
  non-delta layer information.

* Kvt: Merge `LayerDeltaRef` into `LayerRef`

why:
  No need to maintain nested object refs (as with `Aristo`)

* Kvt: Re-write balancer logic similar to `Aristo`

why:
  Although `Kvt` was a cheap copy of `Aristo` it sort of got out of
  sync and the balancer code was wrong.

* Update iterator over forked peers

why:
  Yield additional field `isLast` indicating that the last iteration
  cycle was approached.

* Optimise balancer calculation.

why:
  One can often avoid providing a new object containing the merge of two
  layers for the balancer. This avoids copying tables. In some cases this
  is replaced by `hasKey()` look ups though. One uses one of the two
  to combine and merges the other into the first.

  Of course, this needs some checks for making sure that none of the
  components to merge is eventually shared with something else.

* Fix copyright year
2024-07-18 21:32:32 +00:00

72 lines
2.6 KiB
Nim

# nimbus-eth1
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
# http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
# http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed
# except according to those terms.
import
std/tables,
eth/common,
../kvt_desc
# ------------------------------------------------------------------------------
# Private functions
# ------------------------------------------------------------------------------
proc layersMergeOnto(src: LayerRef; trg: var LayerObj) =
for (key,val) in src.sTab.pairs:
trg.sTab[key] = val
# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------
proc deltaMerge*(
upper: LayerRef; # Think of `top`, `nil` is ok
modUpperOk: bool; # May re-use/modify `upper`
lower: LayerRef; # Think of `balancer`, `nil` is ok
modLowerOk: bool; # May re-use/modify `lower`
): LayerRef =
## Merge argument `upper` into the `lower` filter instance.
##
## Note that the namimg `upper` and `lower` indicate that the filters are
## stacked and the database access is `upper -> lower -> backend`.
##
if lower.isNil:
# Degenerate case: `upper` is void
result = upper
elif upper.isNil:
# Degenerate case: `lower` is void
result = lower
elif modLowerOk:
# Can modify `lower` which is the prefered action mode but applies only
# in cases where the `lower` argument is not shared.
layersMergeOnto(upper, lower[])
result = lower
elif not modUpperOk:
# Cannot modify any argument layers.
result = LayerRef(sTab: lower.sTab)
layersMergeOnto(upper, result[])
else:
# Otherwise avoid copying some tables by modifyinh `upper`. This is not
# completely free as the merge direction changes to merging the `lower`
# layer up into the higher prioritised `upper` layer (note that the `lower`
# argument filter is read-only.) Here again, the `upper` argument must not
# be a shared layer/filter.
for (key,val) in lower.sTab.pairs:
if not upper.sTab.hasKey(key):
upper.sTab[key] = val
result = upper
# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------