Goal

Implement the MSETEX command as described in Redis documentation.

Command Syntax

MSETEX numkeys key value [key value ...] [NX|XX] [EX seconds|PX milliseconds|EXAT timestamp|PXAT timestamp|KEEPTTL]

Implementation Details

1. Command Registration:

   • Register MSETEX in src/server/command_registry.cc (or string_family.cc registration block).
   • It should be a write command.

2. Implementation in src/server/string_family.cc:

   • Implement a new function MSetEx (or similar) to handle the command.
   • Argument Parsing:
     • Parse numkeys to determine how many key-value pairs to expect.
     • Parse the key-value pairs.
     • Parse the optional arguments (expiration, NX/XX, KEEPTTL) into SetCmd::SetParams.
   • Logic:
     • The existing OpMSet function currently iterates over keys and calls SetCmd::Set with default parameters.
     • Refactor OpMSet to accept SetCmd::SetParams as an argument, or create a new OpMSetEx function that does so.
     • Ensure the operation is atomic (runs in a single hop/transaction), similar to MSET.
     • Use SetCmd class which already handles the logic for setting values with options.

3. Tests:

   • Add unit tests in src/server/string_family_test.cc covering:
     • Basic usage with expiration.
     • NX and XX options.
     • KEEPTTL option.
     • Invalid arguments (wrong numkeys, invalid options).
     • Atomicity (all or nothing, though hard to test directly in unit tests, verify behavior).

References

• src/server/string_family.cc: OpMSet, SetCmd
• https://redis.io/docs/latest/commands/msetex/