feat: add optional JSON functions support

[crm26]

Which issue does this PR close?

Closes N/A — new feature request.

Rationale

DataFusion Python users currently have no way to query JSON fields in SQL. The datafusion-functions-json crate (under datafusion-contrib) provides json_extract, json_get, ->, ->> and other JSON operators, but these are only available in Rust. This PR exposes them to Python users via an optional feature flag.

What changes are included in this PR?

• Add datafusion-functions-json (v0.53) to workspace dependencies
• Add optional dependency and json feature flag to core crate
• Register JSON functions in SessionContext creation when feature is enabled

3 files changed, 11 insertions.

Are these changes tested?

Not yet — requesting feedback on approach before adding tests. Tests would verify:

• json_extract_string(col, '$.path') works in SQL queries
• Default build (no json feature) compiles and runs without regression
• JSON functions are available immediately after SessionContext() creation

Are there any user-facing changes?

When built with --features json:

from datafusion import SessionContext

ctx = SessionContext()
# JSON extraction now available in SQL
result = ctx.sql("""
    SELECT json_extract_string(data, '$.address.state') as state,
           COUNT(*) as cnt
    FROM my_table
    GROUP BY state
""").collect()

Default builds are unaffected.

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com

[timsaucer]

Sounds like a very nice feature to have, but it would mean that we're now pulling in non-official code/functions into the official release. I don't know if that's a hard blocker, but I do want to bring the topic up on the mailing list for a wider audience before we merge this. I'm moving it to draft for that reason.

[timsaucer]

Also for this PR to go in we would want first class dataframe API support and not just SQL support and unit tests to cover. Since you're using claude you might be able to use at least portions of the skill I've started working on #1460 to help write those pieces.

But first let's get a temperature read on the community. I'm 50/50 on the idea.

[crm26]

Thanks Tim. I have use cases that need json support. I am seeing a material speed up using dataforge over duckdb with the unofficial library. Let me know how I can help. Thanks, Christian

…

On Mon, Mar 30, 2026 at 8:32 AM Tim Saucer ***@***.***> wrote: *timsaucer* left a comment (apache/datafusion-python#1466) <#1466?email_source=notifications&email_token=AN334FEZ4F6OQHS7KAPXFA34TJSPBA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIMJVGQ3DSNJSGQ22M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2LK4DSL5RW63LNMVXHIX3POBSW4X3DNRUWG2Y#issuecomment-4154695245> Also for this PR to go in we would want first class dataframe API support and not just SQL support and unit tests to cover. Since you're using claude you might be able to use at least portions of the skill I've started working on #1460 <#1460> to help write those pieces. But first let's get a temperature read on the community. I'm 50/50 on the idea. — Reply to this email directly, view it on GitHub <#1466?email_source=notifications&email_token=AN334FEZ4F6OQHS7KAPXFA34TJSPBA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIMJVGQ3DSNJSGQ22M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2LK4DSL5RW63LNMVXHIX3POBSW4X3DNRUWG2Y#issuecomment-4154695245>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AN334FDWMPAR3GHPSLYMINL4TJSPBAVCNFSM6AAAAACXGBYRJKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DCNJUGY4TKMRUGU> . You are receiving this because you authored the thread.Message ID: ***@***.***>