Databases

SQL, NoSQL, schema design, migrations, ORMs, and database operations

skills in category: 4,325
pages available: 181

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Db Isolation SelectionA> Selecting the right isolation level requires matching the workload's correctness requirements against the performance cost and retry complexity of stricter levels.databasessqldebuggingVotes: 0GitHub stars: 20
Db Isolation LevelsA> The four SQL standard isolation levels control which concurrent transaction side-effects are visible, with PostgreSQL implementing them via MVCC snapshots rather than traditional locking.databasessqldebuggingVotes: 0GitHub stars: 20
Db Horizontal ShardingA> Distributing rows of a table across multiple database instances (shards) to scale beyond the capacity of a single server, with careful attention to shard key selection and cross-shard query complexity.databasespythongoVotes: 0GitHub stars: 20
Db Hierarchical DataA> Choosing between adjacency list, nested sets, closure table, and materialized path based on read/write ratio, query patterns, and tree depth.databasesgosqlVotes: 0GitHub stars: 20
Db Hash IndexA> Optimized for equality-only lookups with O(1) average access time, hash indexes are smaller than B-tree when range queries and ordering are never needed.databasessqlapiVotes: 0GitHub stars: 20
Db Graph In RelationalA> Modeling vertices and edges in SQL tables for social graphs, dependency networks, and recommendation systems with recursive queries -- and knowing when SQL stops being practical.databasesgosqlVotes: 0GitHub stars: 20
Db First Normal FormA> Every column holds a single atomic value, no repeating groups exist, and every row is uniquely identifiable by a primary key.databasesgosqlVotes: 0GitHub stars: 20
Db Expression IndexA> Indexes on computed expressions and specialized index types (GIN, GiST) for non-scalar data like JSONB, arrays, and full-text search.databasesgosqlVotes: 0GitHub stars: 20
Db Explain ReadingA> How to read query execution plans to identify performance bottlenecks, row count misestimations, and missing indexes.databasesgosqlVotes: 0GitHub stars: 20
Db Expand ContractA> Add new structure, migrate data, remove old structure -- the three-phase pattern for safe column renames, type changes, and table restructuring.databasesrustsqlVotes: 0GitHub stars: 20
Db Entity Attribute ValueA> A schema pattern for storing dynamic, user-defined attributes as rows instead of columns -- usually avoided in favor of JSONB or polymorphic alternatives, but occasionally justified for genuinely unbounded attribute sets.databasesgosqlVotes: 0GitHub stars: 20
Db Document In RelationalA> Using JSONB columns to store semi-structured data alongside relational tables, with indexing strategies and guidelines for when to embed vs normalize.databasesgosqlVotes: 0GitHub stars: 20
Db DenormalizationA> Intentionally introducing controlled redundancy into a normalized schema to eliminate expensive joins or aggregations, applied only after measured proof of a performance problem.databasesgosqlVotes: 0GitHub stars: 20
Db Deadlock PreventionA> Deadlocks occur when two or more transactions hold locks and each waits for a lock the other holds; prevention through consistent lock ordering and detection through timeout-based abort resolves them.databasesgosqlVotes: 0GitHub stars: 20
Db Composite IndexA> Multi-column indexes that accelerate queries filtering on column combinations, governed by the leftmost prefix rule and the ESR (Equality, Sort, Range) column ordering strategy.databasesgosqlVotes: 0GitHub stars: 20
Db Closure TableA> Storing all ancestor-descendant pairs in a separate table for O(1) subtree and ancestor lookups with manageable write costs.databasesgosqlVotes: 0GitHub stars: 20
Db Cap TheoremA> In a distributed system, when a network partition occurs, you must choose between consistency (every read returns the most recent write) and availability (every non-failing node returns a response) -- you cannot have both simultaneously.databasesgosqlVotes: 0GitHub stars: 20
Db Audit TrailA> Recording who changed what, when, and why, using trigger-based or application-level change tracking with immutable append-only logs.databasesgosqlVotes: 0GitHub stars: 20
Db Acid PropertiesA> ACID guarantees that database transactions are processed reliably: each transaction is all-or-nothing (Atomic), leaves the database in a valid state (Consistent), operates as if no other transactions are running (Isolated), and once committed, persists even through crashes (Durable).databasesgosqlVotes: 0GitHub stars: 20
Db Acid In PracticeA> The mechanisms that make ACID guarantees real: Write-Ahead Logging ensures atomicity and durability, fsync ensures persistence to physical media, and crash recovery replays the WAL to restore a consistent state.databasesgobashVotes: 0GitHub stars: 20
Api Pagination OffsetA> OFFSET/LIMIT PAGINATION IS THE SIMPLEST PAGINATION MODEL BUT CARRIES HIDDEN COSTS — COUNT(\*) QUERIES ARE EXPENSIVE ON LARGE TABLES, CONCURRENT INSERTS AND DELETES CAUSE PAGE DRIFT THAT DUPLICATES OR SKIPS ROWS, AND HIGH OFFSETS FORCE FULL INDEX SCANS THAT MAKE DEEP PAGES ORDERS OF MAGNITUDE SLOWER THAN PAGE ONE.databasesgosqlVotes: 0GitHub stars: 20
Api Pagination KeysetA> KEYSET PAGINATION NAVIGATES LARGE RESULT SETS BY REMEMBERING THE LAST SEEN ROW'S SORT KEY RATHER THAN COUNTING SKIPPED ROWS — EACH PAGE QUERY BECOMES AN EFFICIENT INDEX SEEK THAT PERFORMS IDENTICALLY WHETHER YOU ARE ON PAGE 1 OR PAGE 1,000,000, MAKING IT THE ONLY PAGINATION STRATEGY THAT SCALES RELIABLY BEYOND TEN MILLION ROWS.databasessqlexpressVotes: 0GitHub stars: 20
Api Pagination CursorA> CURSOR-BASED PAGINATION REPLACES NUMERIC OFFSETS WITH OPAQUE POSITION TOKENS — EACH CURSOR ENCODES EXACTLY WHERE THE CLIENT LEFT OFF, ELIMINATING PAGE DRIFT WHEN ROWS ARE INSERTED OR DELETED BETWEEN REQUESTS AND ENABLING CONSISTENT TRAVERSAL OF LIVE DATASETS.databasesrustgoVotes: 0GitHub stars: 20
Api Idempotency KeysA> IDEMPOTENCY KEYS ARE A SAFETY CONTRACT — THEY ALLOW CLIENTS TO SAFELY RETRY FAILED OR AMBIGUOUS REQUESTS WITHOUT RISK OF DUPLICATE SIDE EFFECTS, AND THE DIFFERENCE BETWEEN AT-LEAST-ONCE AND EXACTLY-ONCE SEMANTICS IS ENTIRELY DETERMINED BY WHETHER THE SERVER STORES AND ENFORCES IDEMPOTENCY KEY UNIQUENESS WITHIN THE CONFIGURED TTL WINDOW.databasesgosqlVotes: 0GitHub stars: 20