The string representation of `long double` may take
up to ~5000 chars (see PR #3745).
Before this fix HINCRBYFLOAT would never overflow (since
the string could not exceed 256 chars). Now it can.
This is the first step towards getting rid of HMSET which is a command
that does not make much sense once HSET is variadic, and has a saner
return value.
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.
1. HVSTRLEN -> HSTRLEN. It's unlikely one needs the length of the key,
not clear how the API would work (by value does not make sense) and
there will be better names anyway.
2. Default is to return 0 when field is missing.
3. Default is to return 0 when key is missing.
4. The implementation was slower than needed, and produced unnecessary COW.
Related issue #2415.
The previous implementation of SCAN parsed the cursor in the generic
function implementing SCAN, SSCAN, HSCAN and ZSCAN.
The actual higher-level command implementation only checked for empty
keys and return ASAP in that case. The result was that inverting the
arguments of, for instance, SSCAN for example and write:
SSCAN 0 key
Instead of
SSCAN key 0
Resulted into no error, since 0 is a non-existing key name very likely.
Just the iterator returned no elements at all.
In order to fix this issue the code was refactored to extract the
function to parse the cursor and return the error. Every higher level
command implementation now parses the cursor and later checks if the key
exist or not.
Previously two string encodings were used for string objects:
1) REDIS_ENCODING_RAW: a string object with obj->ptr pointing to an sds
stirng.
2) REDIS_ENCODING_INT: a string object where the obj->ptr void pointer
is casted to a long.
This commit introduces a experimental new encoding called
REDIS_ENCODING_EMBSTR that implements an object represented by an sds
string that is not modifiable but allocated in the same memory chunk as
the robj structure itself.
The chunk looks like the following:
+--------------+-----------+------------+--------+----+
| robj data... | robj->ptr | sds header | string | \0 |
+--------------+-----+-----+------------+--------+----+
| ^
+-----------------------+
The robj->ptr points to the contiguous sds string data, so the object
can be manipulated with the same functions used to manipulate plan
string objects, however we need just on malloc and one free in order to
allocate or release this kind of objects. Moreover it has better cache
locality.
This new allocation strategy should benefit both the memory usage and
the performances. A performance gain between 60 and 70% was observed
during micro-benchmarks, however there is more work to do to evaluate
the performance impact and the memory usage behavior.
When keyspace events are enabled, the overhead is not sever but
noticeable, so this commit introduces the ability to select subclasses
of events in order to avoid to generate events the user is not
interested in.
The events can be selected using redis.conf or CONFIG SET / GET.
The ziplist -> hashtable conversion code is triggered every time an hash
value must be promoted to a full hash table because the number or size of
elements reached the threshold.
If a problem in the ziplist causes the same field to be present
multiple times, the assertion of successful addition of the element
inside the hash table will fail, crashing server with a failed
assertion, but providing little information about the problem.
This code adds a new logging function to perform the hex dump of binary
data, and makes sure that the ziplist -> hashtable conversion code uses
this new logging facility to dump the content of the ziplist when the
assertion fails.
This change was originally made in order to investigate issue #547.
To improve the performance of the ziplist implementation, some
functions have been converted to macros to avoid unnecessary stack
movement and duplicate variable assignments.
