RISQ DB

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Questions and Answers

Which storage engine does rdb use as its underlying storage engine?

  • Oracle
  • MySQL
  • MongoDB
  • LMDB (correct)

What does rdb provide to any process running as part of a trading platform deployment?

  • A way to store data in a relational database
  • A common way to communicate with other processes
  • A way to cache data using flexible indexes (correct)
  • A way to run SQL queries

What type of data structure does LMDB use to store key-value pairs?

  • Binary tree
  • Hash table
  • Linked list
  • B+-tree (correct)

How does LMDB store values inline to the keys?

<p>Inline to the keys (A)</p> Signup and view all the answers

How many read/write transactions are allowed in LMDB at a time?

<p>Only one (A)</p> Signup and view all the answers

Which database is used as the underlying storage engine for rdb?

<p>LMDB (D)</p> Signup and view all the answers

What does rdb provide to any process running as part of a trading platform deployment?

<p>A common way to cache data (C)</p> Signup and view all the answers

What type of indexes can be built using rdb?

<p>B+-tree indexes (A)</p> Signup and view all the answers

How does LMDB ensure low latency reads and writes?

<p>By storing values inline to the keys (D)</p> Signup and view all the answers

How many read-only transactions are allowed in LMDB at a time?

<p>Multiple (C)</p> Signup and view all the answers

Which database implementation does rdb use as its underlying storage engine?

<p>LMDB (B)</p> Signup and view all the answers

How does LMDB ensure low latency reads and writes?

<p>By using a B+-tree data structure (B)</p> Signup and view all the answers

How many subdatabases does rdb use within an LMDB instance?

<p>1 (C)</p> Signup and view all the answers

Which method is used to find a record by order_id in the database?

<p>order.db_find('by_order_id', cursor) (A)</p> Signup and view all the answers

What is the purpose of the 'insert_order' function?

<p>To insert a new record into the 'order' table (C)</p> Signup and view all the answers

What does the 'update_order' function do when the record already exists in the database?

<p>Updates the record with the new values (B)</p> Signup and view all the answers

Which file is managed by the LMDB library to keep track of open transactions?

<p>Lock file (C)</p> Signup and view all the answers

What is the recommended size per key/value combination in LMDB?

<p>Less than 1KB (D)</p> Signup and view all the answers

What happens to values that exceed the maximum value size in LMDB?

<p>They are stored in overflow pages (D)</p> Signup and view all the answers

What happens to the on-disk size of the database in LMDB?

<p>It will always be larger than the size of the data stored within (C)</p> Signup and view all the answers

Match the following database terms and concepts with their descriptions:

<p>LMDB = A high-performance, transactional key-value store with a unique memory-mapped file design db_key = A subset of the fields of the db_record instance that it is the key for db_record = A value that can contain a number of fields, as well as a small header that contains some additional meta data by_rec_num = A type of db_key that is used as the primary index for all db_record’s</p> Signup and view all the answers

Match the following database best practices with their descriptions:

<p>Avoid long write transactions = To prevent locking the database for a long period of time Break write transactions into smaller units = To allow other processes to interleave writes Remove corrupted database lock file = Once the database isn’t in use Reuse nodes with no data = Using a freelist of pages</p> Signup and view all the answers

Match the following record types with their corresponding key types in rdb:

<p>order = by_timestamp</p> Signup and view all the answers

Match the following record fields with their data types in rdb:

<p>order_id = i64 client_order_id = s64 revision_number = i16 price = dbl</p> Signup and view all the answers

Match the following database operations with their corresponding SQL statements:

<p>Insert a record = INSERT INTO order (order_id, client_order_id, revision_number, price, quantity, state) VALUES ($1, $2, $3, $4, $5, $6) Update a record = INSERT INTO order (order_id, client_order_id, revision_number, price, quantity, state) VALUES ($1, $2, $3, $4, $5, $6) ON CONFLICT (order_id) DO UPDATE Select a record = SELECT * FROM order WHERE order_id = $1 Delete a record = Not mentioned in the text</p> Signup and view all the answers

Match the following Python functions with their corresponding database operations:

<p>find_by_order_id = Select a record insert_order = Insert a record update_order = Update a record delete_order = Delete a record</p> Signup and view all the answers

Match the following LMDB concepts with their corresponding descriptions:

<p>Database = A collection of key-value pairs Transaction = A unit of work performed on the database Cursor = An object used to read and modify the database Subdatabase = A separate, independent part of the main database</p> Signup and view all the answers

Match the following concepts from the text with their descriptions:

<p>rdb = Our proprietary record-based database that provides a common transient data storage layer and event sourcing backbone LMDB = The underlying storage engine for rdb that uses a B+-tree to store key-value pairs B+-tree = A data structure used by LMDB to store key-value pairs, with the values stored inline to the keys up to a compile-time defined size subdatabase = A feature of LMDB that allows for up to 16 databases within a single database file</p> Signup and view all the answers

Match the following LMDB features with their descriptions:

<p>Page cache = B+-trees used by LMDB are page cache friendly, resulting in low latency reads and writes without requiring additional tuning Transactions = LMDB allows for a single read/write transaction and many read-only transactions, with other potential writers blocked during a read/write transaction Database file = An LMDB instance is a single file on disk, and when a process opens the database, mmap is called to map the database file into process memory Node size = Each node of the B+-tree in LMDB is allocated at the operating system's page size, typically 4KB</p> Signup and view all the answers

Match the following rdb features with their descriptions:

<p>Common way for processes to communicate and cache data = rdb provides this using strong record definitions and flexible indexes Single subdatabase = rdb only ever uses a single subdatabase within an LMDB instance Compile-time defined size = LMDB stores values inline to the keys up to this size Page cache leverage = LMDB's node size matching the page size allows it to leverage the page cache to its full potential</p> Signup and view all the answers

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