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Add support for IS NULL and IS NOT NULL comparators in experiment tags#21148

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TomeHirata merged 8 commits intomlflow:masterfrom
TomeHirata:feat/experiment/null-search
Feb 26, 2026
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Add support for IS NULL and IS NOT NULL comparators in experiment tags#21148
TomeHirata merged 8 commits intomlflow:masterfrom
TomeHirata:feat/experiment/null-search

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@TomeHirata TomeHirata commented Feb 26, 2026

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n/a

What changes are proposed in this pull request?

As titled

How is this PR tested?

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Does this PR require documentation update?

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  • area/tracking: Tracking Service, tracking client APIs, autologging
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  • area/model-registry: Model Registry service, APIs, and the fluent client calls for Model Registry
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@TomeHirata
Add support for IS NULL and IS NOT NULL comparators in experiment tag…
43d6e08 
… searches

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
@github-actions github-actions bot added size/M v3.10.1 area/tracking Tracking service, tracking client APIs, autologging rn/none List under Small Changes in Changelogs. labels Feb 26, 2026
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github-actions bot commented Feb 26, 2026

🛠 DevTools 🛠

Install mlflow from this PR

# mlflow
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/21148/merge
# mlflow-skinny
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/21148/merge#subdirectory=libs/skinny

For Databricks, use the following command:

%sh curl -LsSf https://raw.githubusercontent.com/mlflow/mlflow/HEAD/dev/install-skinny.sh | sh -s pull/21148/merge

Copilot AI reviewed Feb 26, 2026
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Pull request overview

This pull request adds support for IS NULL and IS NOT NULL operators for filtering experiment tags in MLflow's search functionality. The feature allows users to query for experiments that either have or don't have specific tags, regardless of their values.

Changes:

  • Extended the search token parser to recognize IS NULL and IS NOT NULL as valid comparison operators for tags
  • Added validation to restrict these operators to tags only (not attributes)
  • Implemented filtering logic for both SQL-backed stores (using EXISTS subqueries) and file-backed stores (using dictionary membership checks)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File Description
mlflow/utils/search_utils.py Extended token parsing to handle IS NULL/IS NOT NULL operators, added validation to restrict usage to tags only, implemented filtering logic for file-based stores
mlflow/store/tracking/sqlalchemy_store.py Implemented SQL EXISTS subquery-based filtering for IS NULL/IS NOT NULL operators on experiment tags
tests/store/tracking/test_sqlalchemy_store.py Added comprehensive test coverage including standalone, combined, and error cases for IS NULL/IS NOT NULL operators
tests/store/tracking/test_file_store.py Added test coverage for IS NULL/IS NOT NULL operators (missing one combined test case present in SQL store tests)

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b89fefe 
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
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github-actions bot commented Feb 26, 2026 •
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@TomeHirata
Add IS NULL and IS NOT NULL comparators for tag searches in documenta…
41a3e4c 
…tion

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
WeichenXu123
WeichenXu123 reviewed Feb 26, 2026
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WeichenXu123
WeichenXu123 reviewed Feb 26, 2026
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mlflow/utils/search_utils.py Outdated


def _join_in_comparison_tokens(tokens, search_traces=False):
def _join_in_comparison_tokens(tokens, search_traces=False, search_null_operators=False):
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@WeichenXu123 WeichenXu123 Feb 26, 2026 •
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The new parameter search_null_operators is a bit ambiguous — it could be read as "search for null operators." Something
like support_null_cmp_operator would be clearer.

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@TomeHirata TomeHirata Feb 26, 2026 •
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Actually I removed search_null_operators at all since this guard is not needed

@TomeHirata
remove search_null_operators
c01e6aa 
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
serena-ruan
serena-ruan reviewed Feb 26, 2026
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mlflow/utils/search_utils.py
stripped_comparison = [token for token in comparison.tokens if not token.is_whitespace]

# Handle IS NULL / IS NOT NULL (2 tokens: identifier + comparator, no value)
if len(stripped_comparison) == 2:
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Should we override _validate_comparison instead?

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@TomeHirata TomeHirata Feb 26, 2026

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good call

serena-ruan
serena-ruan approved these changes Feb 26, 2026
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Overall LGTM!

TomeHirata and others added 2 commits February 26, 2026 17:27
@TomeHirata @claude
Address PR review comments
e084379 
- Add missing 'combined with value filter' test case to file store
  (matching sqlalchemy store test coverage)
- Refactor IS NULL/IS NOT NULL handling to override _validate_comparison
  instead of pre-checking len in _get_comparison

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
@TomeHirata
lint
ef01b0c 
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
@TomeHirata
refactor
2aafdc7 
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
@TomeHirata
refactor
f6c3d7a 
Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
@TomeHirata TomeHirata added this pull request to the merge queue Feb 26, 2026
Merged via the queue into mlflow:master with commit 3d98108 Feb 26, 2026
51 of 52 checks passed
@TomeHirata TomeHirata deleted the feat/experiment/null-search branch February 26, 2026 11:52
@github-actions github-actions bot added size/L Large PR (200-499 LoC) and removed size/M labels Feb 26, 2026
daniellok-db pushed a commit to daniellok-db/mlflow that referenced this pull request Mar 5, 2026
@TomeHirata @claude @daniellok-db
Add support for IS NULL and IS NOT NULL comparators in experiment tags (
5409f22 
mlflow#21148)

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
daniellok-db pushed a commit to daniellok-db/mlflow that referenced this pull request Mar 5, 2026
@TomeHirata @claude @daniellok-db
Add support for IS NULL and IS NOT NULL comparators in experiment tags (
fa2ce7b 
mlflow#21148)

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
daniellok-db pushed a commit that referenced this pull request Mar 5, 2026
@TomeHirata @claude @daniellok-db
Add support for IS NULL and IS NOT NULL comparators in experiment tags (
a223d4a 
#21148)

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
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@serena-ruan serena-ruan serena-ruan approved these changes

@harupy harupy Awaiting requested review from harupy

@B-Step62 B-Step62 Awaiting requested review from B-Step62

@WeichenXu123 WeichenXu123 Awaiting requested review from WeichenXu123

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