---
type: concept
x-llmwiki:
  schemaVersion: "0.1"
  contentHash: cd416c0d2a7f39e07b92d8bb11c7116fce6a2fbcfb00b7bad54b6e9d9eaacee5
  pageDirectory: concepts
  sources:
    - delta_duplicate_columns_found-error-condition-databricks-on-aws.md
  confidence: 0.85
  provenanceState: extracted
  freshnessStatus: unverified
  aliases:
    - delta-lake-partitioning-constraints
    - DLPC
    - Delta Lake Constraints
    - Delta Lake Partitioning
    - Delta Lake partitioning
  citations:
    - file: delta_duplicate_columns_found-error-condition-databricks-on-aws.md
title: Delta Lake Partitioning Constraints
description: The requirement that partition columns and partition schemas in Delta Lake must not contain duplicate column definitions, enforced by the PARTITION_COLUMNS and PARTITION_SCHEMA sub-reasons of DELTA_DUPLICATE_COLUMNS_FOUND.
tags:
  - delta-lake
  - partitioning
  - schema-constraints
timestamp: "2026-06-19T15:04:17.877Z"
---

# Delta Lake Partitioning Constraints

**Delta Lake Partitioning Constraints** refer to the rules and error conditions that enforce a valid partitioning schema in [Delta Lake] tables. The DELTA_DUPLICATE_COLUMNS_FOUND error condition is the primary mechanism for flagging violations of these constraints when duplicate column definitions are detected in partition-related contexts. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Constraint Categories

The error condition defines two distinct subcategories that correspond to different stages of partitioning:

- **`PARTITION_COLUMNS`** — Raised when duplicate column names appear in the partition column specification (e.g., in a `PARTITIONED BY` clause). ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]
- **`PARTITION_SCHEMA`** — Raised when the partition schema itself contains duplicate column definitions, meaning the logical structure that maps partition columns to their types and positions has duplicates. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

Both subtypes produce the same SQLSTATE (42711) and error message prefix: `Found duplicate column(s): <duplicateCols>`. The context of the error tells the user whether the duplicate was found in the partition columns directly or in the partition schema metadata. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Enforcement

Delta Lake enforces these constraints at write time (during `INSERT`, `ALTER TABLE`, or schema evolution operations) to prevent ambiguous or invalid partitioning structures. If a duplicate is detected, the operation fails with `DELTA_DUPLICATE_COLUMNS_FOUND` and the corresponding subtype. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

Users must ensure that each partition column name appears exactly once in the partition specification and that the inferred partition schema (derived from the table’s existing partitioning or from a `CONVERT TO DELTA` operation) contains no duplicate entries. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Related Concepts

- [Delta Lake](/concepts/delta-lake.md) – The storage layer that enforces these constraints.
- Schema Enforcement – Broader mechanism for ensuring data conforms to a table’s schema.
- Partitioning in Delta Lake – Best practices for setting partition columns.
- DELTA_DUPLICATE_COLUMNS_FOUND error condition – Full error reference, including other subtypes such as `ADDING_COLUMNS`, `DATA`, and `TABLE_SCHEMA`.

## Sources

- delta_duplicate_columns_found-error-condition-databricks-on-aws.md

# Citations

1. [delta_duplicate_columns_found-error-condition-databricks-on-aws.md](/references/delta_duplicate_columns_found-error-condition-databricks-on-aws-42950ac1.md)
