hash schema: prune state failed

[zzzckck]

System information

Geth version: geth v1.4.11
OS & Version: Windows/Linux/OSX
Commit hash : (if develop)

Although hash schema & levelDB is no longer supported, at current stage, we still hope it can work, including operations like: prune state

Steps to reproduce the behaviour

note: in my env, I use --triesInMemory 32, not sure if it matters or not.

1.setup a BSC full node
2.enable flag: --pruneancient --syncmode full
3.do prune state: ./bsc snapshot prune-state --datadir <datadir>
will report this error and failed:

INFO [07-17|02:42:20.876] Smartcard socket not found, disabling    err="stat /run/pcscd/pcscd.comm: no such file or directory"
INFO [07-17|02:42:20.879] Set global gas cap                       cap=50,000,000
INFO [07-17|02:42:20.879] Initializing the KZG library             backend=gokzg
INFO [07-17|02:42:21.396] Using leveldb as the backing database
INFO [07-17|02:42:21.396] Allocated cache and file handles         database=/server/geth/chaindata cache=408.00MiB handles=4096
INFO [07-17|02:42:27.029] Using LevelDB as the backing database
WARN [07-17|02:42:27.030] NOTICE: You're opening a pruned disk db!
INFO [07-17|02:42:27.050] Opened ancient database                  database=/server/geth/chaindata/ancient/chain readonly=false frozen=40,449,972
INFO [07-17|02:42:27.074] Snapshot loaded                          diskRoot=388748..a4fa3d root=3c3eac..9565dd
INFO [07-17|02:42:27.754] Initialized state bloom                  size=2.00GiB
ERROR[07-17|02:42:31.100] Failed to prune state                    err="no snapshot paired state"
no snapshot paired state