It's handly to just eval "5+5" without the return and see it printed on
the screen as result. However prepending "return" does not always result
into valid Lua code. So what we do is to exploit a common Lua community
trick of trying to compile with return prepended, and if compilation
fails then it's not an expression that can be returned, so we try again
without prepending "return". Works great apparently.
Maybe there are legitimate use cases for MIGRATE inside Lua scripts, at
least for now. When the command will be executed in an asynchronous
fashion (planned) it is possible we'll no longer be able to permit it
from within Lua scripts.
Thanks to Oran Agra (@oranagra) for reporting. Key extraction would not
work otherwise and it does not make sense to take wrong data in the
command table.
The old version only flushed data to slaves if there were strings
pending in the client->reply list. Now also static buffers are flushed.
Does not help to free memory (which is the only use we have right now in
the fuction), but is more correct conceptually, and may be used in
other contexts.
Arguments arity and arguments type error of redis.call() were not
reported correctly to Lua, so the command acted in this regard like
redis.pcall(), but just for two commands. Redis.call() should always
raise errors instead.
During the refactoring needed for lazy free, specifically the conversion
of t_hash from struct robj to plain SDS strings, HINCRBFLOAT was
accidentally moved away from long doubles to doubles for internal
processing of increments and formatting.
The diminished precision created more obvious artifacts in the way small
numbers are formatted once we convert from decimal number in radix 10 to
double and back to its string in radix 10.
By using more precision, we now have less surprising results at least
with small numbers like "1.23", exactly like in the previous versions of
Redis.
See issue #2846.
An user raised a question about a given behavior of PFCOUNT. Added a
test to show the behavior (union) is correct when most of the items are
in common.
Currently this feature is only accessible via DEBUG for testing, since
otherwise depending on the instance configuration a given script works
or is broken, which is against the Redis philosophy.
By calling redis.replicate_commands(), the scripting engine of Redis
switches to commands replication instead of replicating whole scripts.
This is useful when the script execution is costly but only results in a
few writes performed to the dataset.
Morover, in this mode, it is possible to call functions with side
effects freely, since the script execution does not need to be
deterministic: anyway we'll capture the outcome from the point of view
of changes to the dataset.
In this mode math.random() returns different sequences at every call.
If redis.replicate_commnads() is not called before any other write, the
command returns false and sticks to whole scripts replication instead.
