Managing Data Catalogs

Guide to selecting, configuring, and using data catalog systems for data discovery, governance, and unified table access across multiple query engines.

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When to Use This Skill

Use this skill when:

• Setting up an Iceberg catalog (Hive Metastore, AWS Glue, REST/Tabular)
• Comparing catalog options for your data platform
• Using DuckDB to unify queries across heterogeneous data sources
• Evaluating open-source metadata discovery tools (DataHub, OpenMetadata)
• Configuring cross-service table access (Athena, EMR, Spark, DuckDB)

Do not use this skill for:

• Table format selection (Delta vs Iceberg) → use @designing-data-storage
• Cloud storage authentication patterns → use @accessing-cloud-storage
• Raw storage I/O without catalog abstraction → use @accessing-cloud-storage
• General ETL pipeline patterns → use @building-data-pipelines

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Quick Catalog Type Comparison

Catalog	Backend	Managed?	Best For
Hive Metastore	RDBMS (Postgres/MySQL)	Self-hosted	Existing Hadoop, high partition counts
AWS Glue	AWS-managed serverless	AWS-managed	AWS-native stacks (Athena, EMR)
Tabular/REST	SaaS (Nessie-backed)	Vendor-managed	Iceberg-native, Git-like branching
DuckDB (embedded)	Local file/Postgres	Self-hosted	Single-user, PoC, small teams

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When to Use Which Catalog

Scenario	Recommended Catalog	Why
AWS-native (Athena, Redshift Spectrum)	AWS Glue	Serverless, IAM integration
Self-hosted Hadoop/Spark	Hive Metastore	Battle-tested, no vendor lock-in
Iceberg-first, multi-cloud	Tabular or Hive	Native Iceberg features or flexibility
Small team, PoC, analytics	DuckDB	Zero infrastructure, SQL-native
LinkedIn-scale metadata	DataHub	Enterprise lineage, scale
Governance-heavy workflows	OpenMetadata	Built-in workflows, data quality

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Core Patterns

Catalog → Table → Storage Mapping

Catalog (name) → Table identifier → Metadata location → Data files
                                    (schema, snapshots, partitions)

Key insight: The catalog stores only metadata pointers. Actual data lives in object storage (S3, GCS, Azure).

Multi-Engine Access Pattern

# Same table, different engines
table = catalog.load_table("db.events")

# PyIceberg → Pandas DataFrame
df = table.scan().to_pandas()

# Spark SQL (via same catalog)
spark.table("db.events")  # Same underlying data

# DuckDB (via ATTACH or REST catalog)
SELECT * FROM iceberg.db.events

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Detailed Guides

Guide	Covers	When to Read
Hive Metastore	Docker deployment, PyIceberg integration, pros/cons	Self-hosting Hadoop/Spark
AWS Glue Catalog	GlueCatalog setup, crawlers, IAM, Unity Catalog federation	AWS-native stacks
REST Catalog & Tabular	Tabular SaaS, Nessie patterns, Git-like branching	Iceberg-first, multi-cloud
DuckDB Multi-Source	ATTACH patterns, unified views, limitations	Single-user/PoC catalog
Open Source Tools	Amundsen vs DataHub vs OpenMetadata comparison	Metadata discovery/governance

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Quick Reference: PyIceberg Catalog Setup

from pyiceberg.catalog import load_catalog

# Hive Metastore
catalog = load_catalog("hive", **{
    "type": "hive",
    "uri": "thrift://localhost:9083",
    "warehouse": "s3://bucket/warehouse/"
})

# AWS Glue
catalog = load_catalog("glue", **{
    "type": "glue",
    "region": "us-east-1",
    "warehouse": "s3://bucket/warehouse/"
})

# REST/Tabular
catalog = load_catalog("rest", **{
    "type": "rest",
    "uri": "https://api.tabular.io/ws/...",
    "token": "tabular-token-...",
    "warehouse": "s3://bucket/warehouse/"
})

# Create and query table
table = catalog.create_table("db.events", schema=schema)
table.append(data)
df = table.scan().to_pandas()

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Best Practices

Catalog Selection

1. Default to Hive Metastore if you have Hadoop investments
2. Use AWS Glue for pure AWS (Athena, EMR, Redshift Spectrum)
3. Choose Tabular for Iceberg-native with branching needs
4. Separate concerns: Iceberg catalog (table storage) ≠ business metadata catalog (OpenMetadata for discovery)

DuckDB-as-Catalog (Development Only)

• Use for single-user notebooks or small team PoC
• Store catalog file in version control (encrypt credentials)
• Use Postgres as DuckLake backend for multi-client writes
• Back up regularly if using as primary catalog

Security

• Never hardcode credentials in catalog configs
• Use IAM roles (AWS), service principals (Azure), or workload identity (GCP)
• Store tokens/secrets in environment variables or secret managers

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See Also

• @designing-data-storage - Delta Lake, Iceberg table formats, file format selection
• @accessing-cloud-storage - fsspec, pyarrow.fs, obstore for storage access
• @building-data-pipelines - ETL patterns using catalog-registered tables

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References

• Apache Iceberg Catalog Documentation
• PyIceberg Catalog API
• DuckDB ATTACH Documentation
• AWS Glue Data Catalog