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OA[CodeSignal] In-Memory Database
Description
Implement a simplified in-memory database that supports record manipulation with various operations. The system should handle basic CRUD operations, conditional updates, filtering, TTL (Time-To-Live), and point-in-time queries.
The database operates on records, where each record is identified by a unique string key. Each record contains multiple field-value pairs, where both field names and values are strings.
All operations include a timestamp parameter (stringified milliseconds). Timestamps are strictly increasing and unique, ranging from 1 to 10^9.
Operations
Level 1: Basic Operations
SET <timestamp> <key> <field> <value>
Insert or update a field-value pair in the record associated with key. If the field exists, replace its value. If the record does not exist, create it.
Returns: Empty string ""
COMPARE_AND_SET <timestamp> <key> <field> <expectedValue> <newValue>
Update field to newValue only if its current value equals expectedValue. If key or field does not exist, or if values don't match, the operation is ignored.
Returns: "true" if updated, "false" otherwise
COMPARE_AND_DELETE <timestamp> <key> <field> <expectedValue>
Delete field only if its current value equals expectedValue. If key or field does not exist, or if values don't match, the operation is ignored.
Returns: "true" if deleted, "false" otherwise
GET <timestamp> <key> <field>
Retrieve the value of field in the record associated with key.
Returns: The value as a string, or empty string "" if not found
Level 2: Filtering (Additional Operation)
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