trino-presto-federated-query

name	trino-presto-federated-query
description	Guides agents through Trino and Presto federated query design. Use when querying across heterogeneous systems, planning semantic consistency, or managing performance and governance in federated analytics.

Trino Presto Federated Query

Overview

Use this skill when Trino or Presto sits across multiple data systems as a federated query layer. It helps agents reason about federation boundaries, predicate pushdown limits, consistency trade-offs, performance planning, and governed consumption patterns.

When to Use

• querying across multiple heterogeneous data stores with Trino or Presto
• defining governed federated analytics access for users or applications
• managing performance, cost, and semantic consistency across systems
• building a query layer over lakehouse tables, relational databases, and object stores
• planning catalog and connector configuration for multi-source environments

Do not use this when all data lives in a single system or when a materialized serving layer would be simpler and more performant.

Workflow

1. Define the federation scope and use case. Include:

   • which data systems are federated (data lake, warehouse, RDBMS, search, cache)
   • what queries need to cross system boundaries
   • who are the consumers (analysts, applications, dashboards)
   • what latency and concurrency expectations exist
   • is federation for ad-hoc exploration or production query patterns

2. Configure catalogs and connectors with explicit assumptions.

   • document which connector is used for each source and its capabilities
   • understand pushdown support per connector: predicates, projections, aggregations, limits
   • define authentication and access control per catalog
   • test connector behavior for null handling, type mapping, and timezone semantics
   • version connector configurations and treat them as infrastructure code

3. Design queries for federation-aware performance.

   • push filtering to the source where possible — cross-system joins are expensive
   • minimize data movement: filter early, aggregate at the source when pushdown supports it
   • avoid joining large datasets across different connectors — materialize one side first
   • use EXPLAIN to verify pushdown behavior before assuming it works
   • set query timeouts and resource limits to prevent runaway federated scans

4. Manage semantic consistency across sources.

   • the same entity in different systems may have different schemas, keys, or freshness
   • define a canonical schema for cross-system entities
   • document freshness differences: real-time source vs daily-refreshed warehouse copy
   • use views or virtual datasets to present consistent semantics to consumers
   • alert when source freshness diverges beyond acceptable thresholds

5. Implement access control and governance.

   • define who can query which catalogs and schemas
   • implement column-level or row-level security where sensitive data is federated
   • audit query patterns: who queries what, how often, and at what cost
   • prevent sensitive data from leaking through cross-system joins
   • document data classification per catalog for security reviews

6. Plan for operations, scaling, and failure modes.

   • define resource groups to isolate workloads and prevent noisy neighbors
   • plan for connector failures: what happens when one source is down?
   • monitor query queue depth, execution time, and memory usage per worker
   • define scaling strategy: add workers vs optimize queries
   • document disaster recovery: can the Trino cluster be rebuilt quickly?
   • plan for catalog and connector upgrades without query disruption

Common Rationalizations

Rationalization	Reality
"Federation means we don't need to move data."	Federation moves data at query time instead of ETL time. Large cross-system joins are often slower and more expensive than materialized copies.
"Trino pushes everything down automatically."	Pushdown depends on the connector and the query pattern. Not all predicates, aggregations, or joins are pushed — verify with EXPLAIN.
"Users can just query everything from one place."	Federated access without governance exposes sensitive data, creates consistency confusion, and generates unexpected costs. Access control is mandatory.
"Performance will be fine because the sources are fast."	Federated query performance depends on network latency, pushdown capability, and data volume. A fast source does not guarantee a fast federated query.

Red Flags

• cross-system joins on large tables without materialization or pre-filtering
• no EXPLAIN verification of pushdown behavior for critical queries
• same entity has conflicting semantics across federated sources with no canonical definition
• no access control beyond "connect to the cluster and query anything"
• resource groups are not configured — one bad query starves all others
• connector failures cause cascading query failures with no graceful degradation
• no monitoring of query cost, duration, or resource consumption per user
• freshness differences between sources are not documented or surfaced to consumers

Verification

• Federation scope, sources, and consumer expectations are documented
• Connector pushdown capabilities are tested and documented per catalog
• Cross-system queries are designed for pushdown and minimize data movement
• Semantic consistency is maintained through canonical schemas or governed views
• Access control and data classification are implemented per catalog
• Resource groups isolate workloads and prevent noisy-neighbor problems
• Operations monitoring covers query performance, failures, and resource usage
• Connector and cluster recovery procedures are documented and tested