Zero-Cost NDV Estimation from Columnar File Metadata
Fuente:
arXiv
Saved in:
| Main Author: | |
|---|---|
| Format: | Preprint |
| Published: |
2026
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866911545008586752 |
|---|---|
| author | Brisson, Claude |
| author_facet | Brisson, Claude |
| contents | We present a method for estimating the number of distinct values (NDV) of a column in columnar file formats, using only existing file metadata--no extra storage, no data access. Two complementary signals are exploited: (1)~inverting the dictionary-encoded storage size equation yields accurate NDV estimates when distinct values are well-spread across row groups; (2)~counting distinct min/max values across row groups and inverting a coupon collector model provides robust estimates for sorted or partitioned data. A lightweight distribution detector routes between the two estimators. While demonstrated on Apache Parquet, the technique generalizes to any format with dictionary encoding and partition-level statistics, such as ORC and F3. Applications include cost-based query optimization, GPU memory allocation, and data profiling. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_24606 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Zero-Cost NDV Estimation from Columnar File Metadata Brisson, Claude Databases 68P15 We present a method for estimating the number of distinct values (NDV) of a column in columnar file formats, using only existing file metadata--no extra storage, no data access. Two complementary signals are exploited: (1)~inverting the dictionary-encoded storage size equation yields accurate NDV estimates when distinct values are well-spread across row groups; (2)~counting distinct min/max values across row groups and inverting a coupon collector model provides robust estimates for sorted or partitioned data. A lightweight distribution detector routes between the two estimators. While demonstrated on Apache Parquet, the technique generalizes to any format with dictionary encoding and partition-level statistics, such as ORC and F3. Applications include cost-based query optimization, GPU memory allocation, and data profiling. |
| title | Zero-Cost NDV Estimation from Columnar File Metadata |
| topic | Databases 68P15 |
| url | https://arxiv.org/abs/2603.24606 |