jev — ask your Postgres tables questions in plain language
Write the condition the way you would say it. Postgres does the rest.
jev lets you filter, rank and classify rows with plain-language conditions. Every row is judged by
TypeSafe's Jev, a System One model that returns calibrated probabilities
instead of generated text. No index, no embeddings, no vector column.
Website: pgjev.com
CREATE EXTENSION jev CASCADE;
SELECT * FROM people WHERE jev(people, 'the name is European');
SELECT subject, jev_prob(tickets, 'the customer is angry') AS p
FROM tickets ORDER BY p DESC LIMIT 20;
SELECT jev_choice(tickets, 'which team should handle this?',
ARRAY['billing', 'technical', 'security', 'sales']) AS team, count(*)
FROM tickets GROUP BY 1;
SELECT name, jev_score(products, 'how luxurious is this product?',
ARRAY['budget', 'mid-range', 'premium', 'luxury']) AS luxury
FROM products ORDER BY luxury DESC;
jev() is an ordinary boolean function, so it composes with everything else in SQL: AND age > 40,
joins, GROUP BY, LIMIT, ORDER BY jev_prob(...).
How it works
jev(table, 'condition') receives the row as a composite value. The first call for a table + condition starts a
read-ahead that streams the table in physical order (TID range scans; OFFSET pages for views).
jev.max_prefetch_rows limits how far it searches for a requested row and how many skipped rows it retains; it
does not limit the answer cache or total session memory.- Rows are packed
jev.batch_size (20) per request into one shared state
({"condition": ..., "rows": [...]}) with one yes/no Noul
question per row. Jev evaluates all questions over one state in parallel, which amortises the ~270-token
request overhead (about 435 tokens for one row alone vs 175 per row in batches of 20).
- Up to 2 ×
jev.concurrency requests are in flight over persistent HTTPS connections, and every row is answered
as soon as its batch returns, so a LIMIT stops the read-ahead after the in-flight window, and rows that cheaper
predicates filter out before jev() runs (WHERE age > 60 AND jev(...)) are skipped rather than judged.
- Answers are cached per row content and question for the backend session, so re-running, changing the threshold or
sorting by probability is free while those answers remain cached. The cache can grow with unique row/question
pairs until
jev_cache_clear() clears it or the backend session ends. Rows from a subquery or CTE (anonymous
record type) can't be read ahead and are judged one request at a time; put jev() on base tables or views when
you can.
Measured on a 2,000-row table from Europe (~190 ms to the API): first run ≈ 3.5 s in 100 requests, ≈ 296k input
tokens, ≈ $0.012; second run ≈ 50 ms; LIMIT 3 on a new condition ≈ 0.6 s. A new condition in a session that
still holds its pooled connections (idle for less than jev.keepalive) takes ≈ 2.3 s: the first request on each
fresh connection is the slow one. Version 0.1.0 needed 8.5 s (and 338k tokens) for the full query and 8.4 s for
the LIMIT.
Why 20 rows per request
Jev has to find rows[i] by position in the array, and that gets unreliable in long arrays. Against ground truth
from structured columns (job title, EU membership, a phrase in a free-text field; 400 rows each), batches of 1–20
rows were 100 % correct, batches of 40 were 92–98 % and batches of 80 were 77–94 %. Wider rows (1,000 characters)
made no difference at 20. Naming rows instead of indexing them did not help. Batches of 20 cost 4 % more tokens than
batches of 40 and are just as fast, because a request's latency barely depends on its size.
Install
Requirements: PostgreSQL 14–17 with plpython3u (package postgresql-plpython3-NN on Debian/Ubuntu,
included in the EDB and Postgres.app builds), a superuser, and a TypeSafe API key from https://console.typesafe.ai.
Managed hosts that withhold superuser or plpython3u (Supabase, Neon, RDS, …) cannot run it; see
Where it runs.
With an AI agent (easiest)
The repo ships an agent skill on skills.sh. Install it into
your project and tell Claude Code, Codex, Cursor or any other skill-aware agent to finish the job:
npx skills add realZachi/pg-jev
Install pgjev on this server and set it up.
The agent runs a preflight (PostgreSQL version, plpython3u, superuser), pgxn install jev or make install against the right
pg_config, CREATE EXTENSION jev CASCADE, places the API key and runs a smoke test. Afterwards it also knows how
to write cost-conscious jev() queries ("find the tickets where the customer threatens to cancel") and to explain
what pgjev can do. The docs are readable as Markdown for agents too: append .md to any page under
https://pgjev.com/docs (see For agents).
From PGXN
pip install pgxnclient # once; also available as `pgxn-client` in Debian/Ubuntu and Homebrew
pgxn install jev # downloads the release from pgxn.org and runs `make install` against pg_config on PATH
psql -c "CREATE EXTENSION jev CASCADE"
Use pgxn install jev --pg_config=/path/to/pg_config (or sudo pgxn install jev) when the server's pg_config
is not on PATH or the extension directory is not writable.
From source (PGXS)
git clone https://github.com/realZachi/pg-jev.git && cd pg-jev
make install # uses pg_config on PATH; or: make install PG_CONFIG=/path/to/pg_config
psql -c "CREATE EXTENSION jev CASCADE" # superuser required (plpython3u is untrusted); CASCADE creates plpython3u
Docker
docker build -t pg-jev . # add --build-arg PG_MAJOR=17 for another major
docker run -d -p 5432:5432 -e POSTGRES_PASSWORD=pw -e TYPESAFE_API_KEY=your-key pg-jev
psql postgres://postgres:pw@localhost/postgres -c "CREATE EXTENSION jev CASCADE"
API key
Either export TYPESAFE_API_KEY in the environment of the PostgreSQL server process, or set it per session
or per role:
SET jev.api_key = 'your-key';
ALTER ROLE analyst SET jev.api_key = 'your-key'; -- persistent, per role
Local Jev-compatible servers
jev.api_url can point at any server that speaks the same POST /v1/systemone contract, so rows never leave
your network and there is no per-row billing. Two such servers are
stuntd (Laya behind the Jev API; it also records answers and trains a
head per question, so a table's decisions can move local over time) and laya-server:
SET jev.api_url = 'http://127.0.0.1:8787/v1/systemone'; -- stuntd's default address
An API key is only required for *.typesafe.ai hosts. For any other host the request is sent without an
Authorization header when no key is set, and with Bearer <key> when one is. The token counts and cost
estimates in jev_stats() and the notices use TypeSafe's list price, whatever the server.
Functions
| Function |
Returns |
Purpose |
jev(row, condition [, threshold]) |
boolean |
WHERE predicate. Threshold: argument → jev.threshold → 0.5 |
jev_prob(row, condition) |
float8 |
Probability 0..1 that the row satisfies the condition |
jev_score(row, question, levels text[]) |
float8 |
Probability-weighted position on ordered levels (0 .. n-1) |
jev_score_norm(row, question, levels) |
float8 |
Same, normalised to 0..1 |
jev_choice(row, question, options text[]) |
text |
The most likely option for the row |
jev_confidence(row, question, kind, options) |
float8 |
Confidence of a score/choice answer |
jev_eval(row, question, kind, options) |
jsonb |
Full raw answer (probabilities, legend, confidence) |
jev_stats() |
jsonb |
Requests, tokens, estimated cost, cache hits, in-flight requests and pooled connections for this session |
jev_cache_clear() |
void |
Forget cached judgments |
jev_version() |
text |
Extension version |
row is the table alias itself (jev(people, ...)) or a subquery alias.
Settings
All settings are plain GUCs: SET jev.<name> = ..., ALTER ROLE ... SET, ALTER DATABASE ... SET, or postgresql.conf.
| Setting |
Default |
Meaning |
jev.api_key |
env TYPESAFE_API_KEY |
TypeSafe API key. Optional when jev.api_url is not a *.typesafe.ai host |
jev.model |
jev-latest |
Model name or pinned version such as jev-1.13.0 |
jev.threshold |
0.5 |
Probability at which jev() returns true |
jev.batch_size |
20 |
Rows per API request. Accuracy drops measurably above ~20–25 (see above) |
jev.concurrency |
16 |
Parallel API requests; up to twice that many are queued ahead of the executor |
jev.max_prefetch_rows |
5000 |
How far read-ahead searches and how many skipped rows it retains; not a bound on the answer cache or total session memory |
jev.notices |
on |
Emit a progress NOTICE per finished request and a summary per table with request count, tokens, estimated cost and time |
jev.api_url |
https://api.typesafe.ai/v1/systemone |
Endpoint (proxies, mocks, local Jev-compatible servers such as stuntd at http://127.0.0.1:8787/v1/systemone; see above) |
jev.timeout |
30 |
Seconds per API request. Waits are interruptible: statement_timeout and cancel requests apply within 250 ms |
jev.keepalive |
600 |
Seconds a pooled API connection may sit idle before it is reconnected. The first request on a fresh connection costs a TLS handshake plus, measured, up to 1.5 s of server-side setup, so keep connections alive across queries; TCP keepalive probes catch silently dropped ones |
jev.max_rows_per_statement |
0 (off) |
Abort a statement that would send more rows than this to the API. Spend guard for shared deployments |
jev.max_chars_per_statement |
0 (off) |
Same, for characters of row data |
Writing good conditions
Jev answers the question you wrote, literally. A few things that help (more in the
TypeSafe docs):
- State the exact condition:
'the customer threatens to leave, dispute a charge, or take legal action'
beats 'churn risk'.
- Keep arithmetic, dates and exact matches in SQL; let the model judge meaning.
- Look at the distribution with
jev_prob() before picking a threshold. Ambiguous cases really do land
near 0.5.
- Send only the columns the judgment needs: create a view with the relevant columns (and any pre-filter) and call
jev(view_alias, ...) on the view. Views are read ahead and batched like tables.
Caveats
- This is a full scan by design: every row the executor asks about goes to the API. Cheaper predicates in the same
WHERE run first and their rejects are skipped; a LIMIT stops early; jev.max_rows_per_statement caps spend.
- Row contents are sent to a third-party API. Do not use it on data you may not share.
- The answer cache lives in the backend session (PL/Python
GD) and can grow with unique row/question pairs;
jev.max_prefetch_rows does not cap it. jev_cache_clear() clears cached answers and read-ahead state for the
current session, and ending the backend session releases the cache. Connection pools with many sessions each warm
their own cache.
plpython3u is an untrusted language: only superusers can create the extension, and functions run with the
server's OS privileges.
Development
make docker-test # builds test/Dockerfile and runs the regression suite (PG_MAJOR=16 by default)
make docker-test PG_MAJOR=17
Locally with a running server and pg_config on PATH:
make install
python3 test/mock_api.py & # deterministic stand-in for the TypeSafe API
make installcheck # pg_regress, tests in test/sql, expected output in test/expected
The regression tests never call the live API. To try the real thing, SET jev.api_key and run any query.
See CONTRIBUTING.md and docs/PUBLISHING.md for release steps.
License
PostgreSQL License. Jev and TypeSafe are trademarks of their respective owners; this project is not
affiliated with TypeSafe.
pg-jev（jev）是一个 PostgreSQL 扩展，让你用自然语言条件代替 SQL 谓词来筛选、排序和分类表中的行。每一行都由 TypeSafe 的 Jev 来判定，这是一个返回校准概率而不是生成文本的模型。