Search results for "reviews"

Skill
Reviews PostgreSQL and MySQL tables (schema.sql, a dump or a pull request's CREATE TABLE) for design flaws that are cheap to fix before data exists - missing primary keys, money in float columns, foreign keys with mismatched types or no index, 32-bit ids, timestamps without time zone, nullable flags, free-text statuses, reserved names and case-sensitive unique emails. Returns corrected DDL. Includes a stdlib Python linter with --self-test.
---
name: sql-schema-design-reviewer
description: Reviews PostgreSQL and MySQL tables (schema.sql, a dump or a pull request's CREATE TABLE) for design flaws that are cheap to fix before data exists - missing primary keys, money in float columns, foreign keys with mismatched types or no index, 32-bit ids, timestamps without time zone, nullable flags, free-text statuses, reserved names and case-sensitive unique emails. Returns corrected DDL. Includes a stdlib Python linter with --self-test.
---

# SQL Schema Design Reviewer

You review database schemas the way an experienced data modeler would at design time: before the first row is written, when changing a type or a key is a one-line edit instead of a weekend migration. You look at the shape of the data (keys, types, constraints, names, indexes), explain the concrete failure each problem leads to, and hand back corrected DDL.

This skill reviews the design of tables. It is not about deploying changes to a live database (locks, backfills, expand/contract rollouts); for that, use a migration safety review.

## Files in this skill

- `scripts/schema_lint.py` - parses CREATE TABLE, CREATE INDEX and ALTER TABLE ... ADD statements and reports keys, types, constraints, naming and index problems with severities and fixes; auto-detects PostgreSQL or MySQL (Python 3 standard library only, no database connection)
- `references/design-rules.md` - every finding code with the failure it causes, when it is acceptable to keep, and the fix
- `references/type-choices.md` - which type to use for ids, money, time, text, flags, statuses and JSON in PostgreSQL and MySQL
- `templates/schema-review.md` - the review to hand back
- `examples/shop-schema.sql` - a small online shop schema with deliberate design flaws
- `examples/shop-schema-fixed.sql` - the same schema after the review; it lints clean

## Workflow

### 1. Get the schema and the context
Ask for the DDL (schema.sql, `pg_dump --schema-only`, `mysqldump --no-data`, or the CREATE TABLE from the pull request), the engine and version, expected row counts per table in a year, and how the data is used (OLTP app, reporting, multi-tenant, replicated, exposed through an ORM). Ask which rules the team already has (UUID vs bigint ids, soft deletes, naming).

### 2. Run the linter
```
python3 scripts/schema_lint.py examples/shop-schema.sql
python3 scripts/schema_lint.py schema.sql --dialect mysql --min-severity MEDIUM
python3 scripts/schema_lint.py db/*.sql --ignore NO_CREATED_AT --json > schema-review.json
python3 scripts/schema_lint.py --self-test
```
Exit 0 means no HIGH findings, 1 means at least one HIGH (use as a CI gate on schema files), 2 means bad input. The linter is heuristic: it reads names (a `price` column in float, an `order_id` without a foreign key), so confirm each finding against the user's intent.

### 3. Review what a script cannot see
Then read the schema yourself (see `references/design-rules.md`):
- Does every table have one clear meaning and a natural unique key besides the surrogate id (sku, email, provider + provider_id)?
- Are relationships right: one-to-many vs many-to-many, ON DELETE behaviour (RESTRICT by default; CASCADE only for true children), nullable foreign keys only where the relation is optional?
- Are invariants in CHECK constraints (quantity > 0, ends_at > starts_at) instead of only in app code?
- Multi-tenant: does every tenant-owned table carry tenant_id, is it in the unique keys and the leading index column?
- Soft deletes: are unique constraints partial (`WHERE deleted_at IS NULL`)?
- Personal data: which columns hold PII, and do they need separate access or retention rules?

### 4. Deliver
Fill `templates/schema-review.md`: verdict, findings ranked by impact with the failure each one causes, then the corrected DDL (see `examples/shop-schema-fixed.sql`) and a list of decisions left to the team. If the tables already hold data, say which fixes now need a migration and flag them for a migration safety review instead of rewriting live tables in place.

## Example result
`examples/shop-schema.sql` (PostgreSQL, 5 tables): 20 findings, 4 HIGH. order_items has no primary key (duplicate lines possible); products.price is double precision and payments.amount is real (cents drift); payments.order_id is integer but references "order".id (bigserial). MEDIUM: serial ids on customers and products, timestamp without time zone on customers.created_at and placed_at, a table named "order" (reserved), foreign keys on "order".customer_id and order_items.order_id with no index. LOW: case-sensitive unique email, varchar(255) habit, nullable is_verified, free-text status, product_id without a foreign key, a redundant payments index, JSON kept in text. `examples/shop-schema-fixed.sql` fixes all of them (orders, bigint identity, numeric(12,2), timestamptz, citext, CHECK on status, composite key on order_items) and lints clean.

## Rules

- Explain each finding as the failure it causes (wrong totals, orphans, duplicate signups, an outage at 2.1 billion ids), not as a style rule.
- Keep the user's conventions (UUID ids, naming) unless they cause a real problem; say when a finding is a judgement call.
- Prefer constraints in the database over checks in the application; the database is the last line of defence.
- Money is exact: numeric/DECIMAL or integer minor units, never float, and store the currency.
- Time is an instant: timestamptz in PostgreSQL, UTC everywhere in MySQL.
- Do not propose changes to tables that already hold production data without pointing out that each one is a migration with its own risks.
FILE:references/design-rules.md
# Design rules and finding codes

| Code | Sev | What goes wrong | Acceptable when | Fix |
|---|---|---|---|---|
| NO_PRIMARY_KEY | HIGH | duplicate rows cannot be told apart or deleted one at a time; logical replication and CDC need a key; ORMs misbehave | never for OLTP tables (staging tables loaded and dropped in one job, maybe) | surrogate `id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY` or a composite natural key (order_id, product_id) |
| FLOAT_MONEY | HIGH | 0.1 + 0.2 = 0.30000000000000004; sums and refunds drift by cents, reports do not tie out | never for money; floats are fine for measurements | `numeric(12,2)` / `DECIMAL(12,2)` or `bigint` minor units (`amount_cents`) plus a currency column |
| FK_TYPE_MISMATCH | HIGH | integer column referencing a bigint key: joins cast, and inserts fail once ids pass 2,147,483,647 | never | same type on both sides |
| MYISAM_ENGINE | HIGH | no transactions, no foreign keys, table locks, corruption on crash | read-only archives, rarely | `ENGINE=InnoDB` |
| INT32_PRIMARY_KEY | MEDIUM | id exhaustion at about 2.1 billion (sequences also skip on rollbacks); the fix is a full table rewrite on the biggest table | small lookup tables (statuses, countries) | `bigint` identity / `BIGINT UNSIGNED AUTO_INCREMENT` |
| TIMESTAMP_WITHOUT_TZ | MEDIUM | the stored value means different instants depending on the writer's zone; DST and server moves corrupt ordering | local wall-clock values that are not instants (store opening hours, a birthday time) | `timestamptz` |
| MONEY_TYPE | MEDIUM | Postgres `money` follows lc_monetary, one currency, rounding on division | never in new schemas | `numeric(12,2)` + currency |
| NULLABLE_AUDIT_COLUMN | MEDIUM | rows without created_at break "last 7 days" reports and backfills | never | `NOT NULL DEFAULT now()` |
| FK_WITHOUT_INDEX | MEDIUM | (PostgreSQL) deleting or updating a parent scans the whole child table under lock; joins from parent to children are slow. MySQL InnoDB creates the index itself | tiny child tables, parents never deleted | index whose leading columns are the FK columns |
| RESERVED_WORD_NAME | MEDIUM | `order`, `user`, `group` must be quoted in every query, ORM, BI tool and ad-hoc psql session | never in new schemas | plural or qualified names: orders, app_users, user_groups, sort_order |
| MYSQL_UTF8MB3 | MEDIUM | `utf8` is 3-byte: emoji and some CJK characters fail or are cut | never in new schemas | `utf8mb4` + `utf8mb4_0900_ai_ci` |
| NULLABLE_BOOLEAN | LOW | three-valued logic: `WHERE NOT is_verified` skips NULL rows | when "unknown" is a real state (then prefer an explicit status) | `NOT NULL DEFAULT false` |
| UNCHECKED_STATUS | LOW | 'Shipped', 'shipped ', 'shiped' all appear; reports split | statuses owned by another system you only mirror | `CHECK (status IN (...))`, an enum type or a lookup table FK |
| MISSING_FOREIGN_KEY | LOW | orphans after deletes, typos in ids, no documented relation | cross-database or event-sourced references; document them | `REFERENCES parent(id)` + index |
| CASE_SENSITIVE_UNIQUE_EMAIL | LOW | Ana@x.com and ana@x.com are two accounts; password resets go to the wrong one | never for login emails | `citext` or `UNIQUE INDEX ON t (lower(email))` and normalize on write |
| VARCHAR_255_HABIT | LOW | in Postgres, 255 is an arbitrary MySQL-era limit; real rules are missing and odd values get rejected | when 255 really is the rule | `text` + `CHECK (char_length(x) <= n)` for real limits |
| REDUNDANT_INDEX | LOW | an index that is a prefix of another (or of the PK) costs writes and memory for nothing | the shorter index is much smaller and very hot | drop it |
| JSON_IN_TEXT | LOW | no validation, no operators, no GIN index | the text is not really JSON | `jsonb` / `JSON` |
| NO_CREATED_AT | LOW | debugging, audits and backfills need to know when rows appeared | pure join tables | `created_at timestamptz NOT NULL DEFAULT now()` |
| MIXED_CASE_NAME | LOW | quoted "OrderItems" must be quoted forever in Postgres | never | snake_case |
| DATETIME_NO_ZONE | LOW | (MySQL) DATETIME has no zone; mixed writers store mixed zones | when every connection sets time_zone='+00:00' | enforce UTC |

## Things the linter cannot judge (review by hand)
- **Keys**: is there a natural unique key besides the surrogate id? Missing `UNIQUE (provider, provider_id)` is how payments get recorded twice.
- **ON DELETE**: RESTRICT/NO ACTION by default; CASCADE only for true child rows (order_items of an order), never from customers to payments.
- **CHECK constraints for invariants**: `quantity > 0`, `ends_at > starts_at`, `discount <= total`.
- **Multi-tenancy**: tenant_id on every tenant table, first in unique keys and indexes, and in every FK (composite FKs prevent cross-tenant references).
- **Soft deletes**: partial unique indexes `WHERE deleted_at IS NULL`, or the email can never be reused.
- **Denormalized totals**: if orders.total is stored, say how it stays equal to the sum of order_items.
- **PII**: list columns with personal data; consider a separate table with stricter access and retention.
FILE:references/type-choices.md
# Type choices (PostgreSQL / MySQL 8)

| Data | PostgreSQL | MySQL 8 | Avoid |
|---|---|---|---|
| Surrogate id | `bigint GENERATED ALWAYS AS IDENTITY` | `BIGINT UNSIGNED AUTO_INCREMENT` | `serial`/`int` on growing tables |
| Public / distributed id | `uuid` (UUIDv7 for index locality, `gen_random_uuid()` for v4) | `BINARY(16)` with UUID_TO_BIN(x, 1) | `varchar(36)` UUIDs (3x bigger, slower) |
| Money | `numeric(12,2)` (or (19,4) for rates) + `currency char(3)` | `DECIMAL(12,2)` + `CHAR(3)` | `float`, `double`, `real`, Postgres `money` |
| Money as integer | `bigint amount_cents` (mind currencies with 0 or 3 decimals) | `BIGINT` | `int` cents (overflows at 21 million) |
| Instant (event happened) | `timestamptz` | `DATETIME(6)` in UTC, or `TIMESTAMP` (2038 limit, converted by session zone) | `timestamp` without time zone |
| Calendar date | `date` | `DATE` | timestamps at midnight |
| Wall-clock time / schedule | `time` + an IANA zone column | `TIME` + zone column | `timetz` |
| Duration | `interval` or integer seconds | `INT` seconds | text like "1h30" |
| Text | `text` (+ CHECK for real limits) | `VARCHAR(n)` with a real n; `TEXT` for long bodies | `varchar(255)` by habit; `char(n)` padding |
| Case-insensitive text (email, username) | `citext` or a `lower()` unique index | case-insensitive `_ci` collation (default) | plain unique on text in Postgres |
| Flag | `boolean NOT NULL DEFAULT false` | `BOOLEAN` (TINYINT(1)) `NOT NULL DEFAULT 0` | nullable booleans, 'Y'/'N' strings |
| Status | `text` + `CHECK (... IN (...))`, enum type, or lookup table | `ENUM(...)` or lookup table | unconstrained text |
| JSON | `jsonb` (GIN index for containment) | `JSON` (generated columns to index) | JSON in text |
| IP address | `inet` / `cidr` | `VARBINARY(16)` with INET6_ATON | text |
| Large binary | object storage + key in a `text` column | same | big BLOBs in hot tables |

## Notes
- Changing a column type later rewrites the table in both engines (with a few exceptions such as widening varchar in Postgres). Get ids and money right first.
- Enum types in Postgres: adding a value is cheap, removing or renaming one is not. Lookup tables are easier to evolve and can carry labels and sort order.
- `NOT NULL` with a sensible default is the norm; nullable should mean "genuinely unknown or not applicable".
- Store the currency next to every amount, even if today there is only one.
- Name things the same everywhere: `customer_id` in every table that references customers, `_at` for instants, `_on` or `_date` for dates, `is_`/`has_` for booleans.
FILE:templates/schema-review.md
# Schema review: <project / schema file>, <date>

**Engine:** <PostgreSQL 16>   **Scope:** <5 tables: customers, products, orders, order_items, payments>
**Context:** <OLTP shop backend, ~2M orders/year, Prisma ORM, no data yet>
**Command:** `python3 scripts/schema_lint.py <shop-schema.sql>`
**Verdict:** <CHANGES NEEDED before the first release: 4 HIGH, 8 MEDIUM, 8 LOW>

## Must fix (HIGH)
| # | Table.column | Finding | What goes wrong | Fix |
|---|---|---|---|---|
| 1 | <products.price> | <FLOAT_MONEY> | <0.1 + 0.2 != 0.3; order totals drift by cents> | <numeric(12,2) NOT NULL CHECK (price >= 0)> |

## Should fix (MEDIUM)
| # | Table.column | Finding | What goes wrong | Fix |
|---|---|---|---|---|
| 1 | <"order"> | <RESERVED_WORD_NAME> | <must be quoted in every query and BI tool> | <rename to orders> |

## Consider (LOW / judgement calls)
- <customers.email: citext so Ana@x.com and ana@x.com are one account>

## Found by reading (not by the linter)
- <payments: add UNIQUE (provider, provider_id) so a webhook retry cannot record a payment twice>
- <ON DELETE: keep RESTRICT on payments -> orders; CASCADE only order_items -> orders>

## Corrected DDL
```sql
<full corrected schema, lints clean>
```

## Decisions for the team
- <bigint identity vs UUIDv7 for public ids>
- <store orders.total or compute it from order_items?>

## If tables already hold data
- <each change above is a migration; list them and run a migration safety review before deploying>
FILE:examples/shop-schema.sql
-- Small online shop schema (PostgreSQL), first draft for review.
-- The problems are deliberate: this is what the skill is meant to catch.

CREATE TABLE customers (
    id          serial PRIMARY KEY,
    email       varchar(255) NOT NULL UNIQUE,
    full_name   varchar(255),
    phone       varchar(255),
    is_verified boolean,
    created_at  timestamp
);

CREATE TABLE products (
    id         serial PRIMARY KEY,
    sku        varchar(64) NOT NULL UNIQUE,
    title      text NOT NULL,
    price      double precision NOT NULL,
    attributes text,
    created_at timestamptz NOT NULL DEFAULT now()
);

CREATE TABLE "order" (
    id          bigserial PRIMARY KEY,
    customer_id integer NOT NULL REFERENCES customers (id),
    status      varchar(20) NOT NULL DEFAULT 'pending',
    total       numeric(12,2) NOT NULL,
    placed_at   timestamp NOT NULL DEFAULT now(),
    created_at  timestamptz NOT NULL DEFAULT now()
);

CREATE TABLE order_items (
    order_id   bigint NOT NULL REFERENCES "order" (id),
    product_id bigint NOT NULL,
    quantity   integer NOT NULL,
    unit_price numeric(12,2) NOT NULL
);

CREATE TABLE payments (
    id          bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    order_id    integer NOT NULL REFERENCES "order" (id),
    amount      real NOT NULL,
    provider    text NOT NULL,
    provider_id text,
    created_at  timestamptz NOT NULL DEFAULT now()
);

CREATE INDEX payments_order_idx ON payments (order_id);
CREATE INDEX payments_order_created_idx ON payments (order_id, created_at);
FILE:examples/shop-schema-fixed.sql
-- Small online shop schema (PostgreSQL), after review.
-- Every change is explained in templates/schema-review.md style in the review.

CREATE EXTENSION IF NOT EXISTS citext;

CREATE TABLE customers (
    id          bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    email       citext NOT NULL UNIQUE,
    full_name   text,
    phone       text CHECK (char_length(phone) <= 32),
    is_verified boolean NOT NULL DEFAULT false,
    created_at  timestamptz NOT NULL DEFAULT now()
);

CREATE TABLE products (
    id         bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    sku        text NOT NULL UNIQUE,
    title      text NOT NULL,
    price      numeric(12,2) NOT NULL CHECK (price >= 0),
    attributes jsonb NOT NULL DEFAULT '{}',
    created_at timestamptz NOT NULL DEFAULT now()
);

CREATE TABLE orders (
    id          bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    customer_id bigint NOT NULL REFERENCES customers (id),
    status      text NOT NULL DEFAULT 'pending'
                CHECK (status IN ('pending', 'paid', 'shipped', 'cancelled', 'refunded')),
    total       numeric(12,2) NOT NULL CHECK (total >= 0),
    placed_at   timestamptz NOT NULL DEFAULT now(),
    created_at  timestamptz NOT NULL DEFAULT now()
);
CREATE INDEX orders_customer_idx ON orders (customer_id);

CREATE TABLE order_items (
    order_id   bigint NOT NULL REFERENCES orders (id),
    product_id bigint NOT NULL REFERENCES products (id),
    quantity   integer NOT NULL CHECK (quantity > 0),
    unit_price numeric(12,2) NOT NULL CHECK (unit_price >= 0),
    created_at timestamptz NOT NULL DEFAULT now(),
    PRIMARY KEY (order_id, product_id)
);
CREATE INDEX order_items_product_idx ON order_items (product_id);

CREATE TABLE payments (
    id          bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    order_id    bigint NOT NULL REFERENCES orders (id),
    amount      numeric(12,2) NOT NULL,
    provider    text NOT NULL,
    provider_id text,
    created_at  timestamptz NOT NULL DEFAULT now(),
    UNIQUE (provider, provider_id)
);
CREATE INDEX payments_order_created_idx ON payments (order_id, created_at);
FILE:scripts/schema_lint.py
#!/usr/bin/env python3
"""SQL schema design linter for PostgreSQL and MySQL DDL (Python 3 standard library only).

Reads CREATE TABLE / CREATE INDEX / ALTER TABLE ... ADD statements (a schema dump,
schema.sql, or the DDL of new tables in a pull request) and reports design problems
that are cheap to fix before data exists and expensive after: tables without a
primary key, money stored in floating point, foreign keys whose type differs from the
referenced key or that have no supporting index (PostgreSQL), *_id columns without a
foreign key, 32-bit primary keys, timestamps without time zone, nullable audit
columns and booleans, unchecked status columns, reserved-word and mixed-case names,
case-sensitive unique emails, redundant indexes, JSON kept in text columns, and MySQL
tables using MyISAM or 3-byte utf8.

It does not connect to a database and does not judge migration safety (locks,
backfills); it reviews the shape of the schema itself.

Usage:
  python3 schema_lint.py FILE.sql [FILE.sql ...] [--dialect auto|postgres|mysql]
        [--min-severity LOW|MEDIUM|HIGH] [--ignore CODE,CODE] [--json]
  python3 schema_lint.py --self-test
Exit codes: 0 = no HIGH findings, 1 = HIGH findings, 2 = bad input (unreadable file,
no CREATE TABLE found).
"""
import argparse, json, re, sys

SEV_ORDER = {"HIGH": 0, "MEDIUM": 1, "LOW": 2}
MONEY_RE = re.compile(r"(^|_)(price|amount|total|subtotal|cost|balance|fee|fees|tax|salary|refund|discount|paid|payment|revenue|credit|debit|charge)(_|$)", re.I)
RESERVED = {"user", "order", "group", "select", "table", "column", "desc", "asc", "check", "default", "from",
            "where", "limit", "offset", "references", "primary", "key", "range", "rank", "window", "all", "both",
            "end", "grant", "to", "type", "values", "constraint", "index", "match", "condition", "interval", "read", "row"}
RESERVED_PG_ONLY_SAFE = {"key", "range", "rank", "type", "values", "match", "condition", "interval", "read", "row", "index"}  # fine unquoted in Postgres
RESERVED_MY_ONLY_SAFE = {"offset", "user", "end", "type", "values", "row"}  # fine unquoted in MySQL 8
STATUS_RE = re.compile(r"^(status|state|kind|role|type|.*_status|.*_state|.*_type)$", re.I)
JSONISH_RE = re.compile(r"(^|_)(json|payload|metadata|meta|attributes|settings|extra|data)$", re.I)
INT32 = {"int", "integer", "int4", "serial", "serial4", "mediumint", "smallint", "int2", "smallserial", "tinyint"}
INT64 = {"bigint", "int8", "bigserial", "serial8"}


def finding(sev, code, table, column, problem, fix, line=0):
    return {"severity": sev, "code": code, "table": table, "column": column, "line": line, "problem": problem, "fix": fix}


def strip_comments(sql):
    out, i, n = [], 0, len(sql)
    while i < n:
        c = sql[i]
        if c in "'\"`":
            j = i + 1
            while j < n and sql[j] != c:
                j += 2 if sql[j] == "\\" and c == "'" else 1
            out.append(sql[i:j + 1]); i = j + 1
        elif sql.startswith("--", i) or c == "#" and (i == 0 or sql[i - 1] in "\n \t"):
            j = sql.find("\n", i); j = n if j < 0 else j
            out.append(" " * (j - i)); i = j
        elif sql.startswith("/*", i):
            j = sql.find("*/", i + 2); j = n if j < 0 else j + 2
            out.append(re.sub(r"[^\n]", " ", sql[i:j])); i = j
        else:
            out.append(c); i += 1
    return "".join(out)


def split_top(s, sep=","):
    parts, depth, cur, q = [], 0, [], None
    for ch in s:
        if q:
            cur.append(ch)
            if ch == q:
                q = None
            continue
        if ch in "'\"`":
            q = ch
        elif ch == "(":
            depth += 1
        elif ch == ")":
            depth -= 1
        if ch == sep and depth == 0:
            parts.append("".join(cur)); cur = []
        else:
            cur.append(ch)
    if "".join(cur).strip():
        parts.append("".join(cur))
    return parts


def statements(sql):
    clean = strip_comments(sql)
    pos = 0
    for part in split_top(clean, ";"):
        line = clean.count("\n", 0, pos + len(part) - len(part.lstrip())) + 1
        pos += len(part) + 1
        if part.strip():
            yield line, part.strip()


def ident(s):
    s = s.strip()
    quoted = s[:1] in "\"`"
    name = s.split(".")[-1].strip().strip("\"`")
    return name, quoted


def cols_list(s):
    return [ident(re.sub(r"\s+(ASC|DESC|NULLS\s+(FIRST|LAST)).*$", "", c.strip(), flags=re.I))[0].lower() if not c.strip().startswith("(") and "(" not in c else c.strip().lower()
            for c in split_top(s)]


class Schema:
    def __init__(self):
        self.tables, self.indexes, self.fks, self.enums = {}, [], [], set()
        self.dialect_hints = {"mysql": 0, "postgres": 0}


def parse(sql):
    sc = Schema()
    if re.search(r"AUTO_INCREMENT|ENGINE\s*=|`|UNSIGNED|DATETIME|TINYINT\(", sql, re.I):
        sc.dialect_hints["mysql"] += 1
    if re.search(r"\bSERIAL\b|BIGSERIAL|TIMESTAMPTZ|JSONB|GENERATED\s+(ALWAYS|BY DEFAULT)\s+AS\s+IDENTITY|::|CREATE\s+TYPE|CITEXT|CONCURRENTLY|\bTEXT\[\]", sql, re.I):
        sc.dialect_hints["postgres"] += 1
    for line, st in statements(sql):
        m = re.match(r"CREATE\s+(?:TEMP(?:ORARY)?\s+|UNLOGGED\s+)?TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?([\w\".`]+)\s*\((.*)\)\s*(.*)$", st, re.I | re.S)
        if m:
            name, quoted = ident(m.group(1))
            t = {"name": name, "quoted": quoted, "line": line, "cols": {}, "order": [], "pk": [], "uniques": [],
                 "checks": " ".join([]), "options": m.group(3), "raw": st}
            checks = []
            for item in split_top(m.group(2)):
                parse_item(item.strip(), t, sc, checks)
            t["checks"] = " ".join(checks).lower()
            sc.tables[name.lower()] = t
            continue
        m = re.match(r"CREATE\s+(UNIQUE\s+)?INDEX\s+(?:CONCURRENTLY\s+)?(?:IF\s+NOT\s+EXISTS\s+)?([\w\".`]*)\s*ON\s+(?:ONLY\s+)?([\w\".`]+)\s*(?:USING\s+\w+\s*)?\((.*)\)\s*(.*)$", st, re.I | re.S)
        if m:
            sc.indexes.append({"table": ident(m.group(3))[0].lower(), "cols": cols_list(m.group(4)), "unique": bool(m.group(1)),
                               "name": ident(m.group(2))[0] if m.group(2) else "", "partial": "where" in m.group(5).lower(), "line": line})
            continue
        m = re.match(r"ALTER\s+TABLE\s+(?:ONLY\s+)?(?:IF\s+EXISTS\s+)?([\w\".`]+)\s+(.*)$", st, re.I | re.S)
        if m:
            tname = ident(m.group(1))[0].lower()
            for action in split_top(m.group(2)):
                a = action.strip()
                am = re.match(r"ADD\s+(?:COLUMN\s+)(?:IF\s+NOT\s+EXISTS\s+)?(.*)$", a, re.I | re.S)
                if am and tname in sc.tables:
                    parse_item(am.group(1), sc.tables[tname], sc, [])
                    continue
                am = re.match(r"ADD\s+(.*)$", a, re.I | re.S)
                if am and tname in sc.tables:
                    chk = []
                    parse_item(am.group(1), sc.tables[tname], sc, chk)
                    sc.tables[tname]["checks"] += " " + " ".join(chk).lower()
            continue
        m = re.match(r"CREATE\s+TYPE\s+([\w\".]+)\s+AS\s+ENUM", st, re.I)
        if m:
            sc.enums.add(ident(m.group(1))[0].lower())
        m = re.match(r"CREATE\s+(?:DOMAIN|EXTENSION)\s+(?:IF\s+NOT\s+EXISTS\s+)?([\w\".]+)", st, re.I)
        if m:
            sc.enums.add(ident(m.group(1))[0].lower())
    return sc


def parse_item(item, t, sc, checks):
    u = item.upper()
    m = re.match(r"CONSTRAINT\s+[\w\"`]+\s+(.*)$", item, re.I | re.S)
    if m:
        item, u = m.group(1).strip(), m.group(1).strip().upper()
    if u.startswith("PRIMARY KEY"):
        t["pk"] = cols_list(re.search(r"\((.*)\)", item, re.S).group(1)); return
    if re.match(r"UNIQUE\b", u):
        cm = re.search(r"\((.*?)\)", item, re.S)
        if cm:
            cols = cols_list(cm.group(1))
            t["uniques"].append(cols)
            sc.indexes.append({"table": t["name"].lower(), "cols": cols, "unique": True, "name": "", "partial": False, "line": t["line"]})
        return
    if u.startswith("FOREIGN KEY"):
        fm = re.match(r"FOREIGN\s+KEY\s*\((.*?)\)\s*REFERENCES\s+([\w\".`]+)\s*(?:\((.*?)\))?", item, re.I | re.S)
        if fm:
            sc.fks.append({"table": t["name"].lower(), "cols": cols_list(fm.group(1)), "ref": ident(fm.group(2))[0].lower(),
                           "ref_cols": cols_list(fm.group(3)) if fm.group(3) else None})
        return
    if u.startswith("CHECK"):
        checks.append(item); return
    if re.match(r"(UNIQUE\s+)?(KEY|INDEX)\b", u) or re.match(r"(FULLTEXT|SPATIAL)\b", u):
        cm = re.search(r"\((.*)\)", item, re.S)
        if cm:
            sc.indexes.append({"table": t["name"].lower(), "cols": cols_list(cm.group(1)), "unique": u.startswith("UNIQUE"),
                               "name": "", "partial": False, "line": t["line"]})
        return
    if u.startswith(("EXCLUDE", "LIKE", "PERIOD")):
        return
    cm = re.match(r"([\"`][^\"`]+[\"`]|[\w$]+)\s+(.*)$", item, re.S)
    if not cm:
        return
    name, quoted = ident(cm.group(1))
    rest = cm.group(2)
    tm = re.match(r"((?:double\s+precision|character\s+varying|bit\s+varying|timestamp(?:\s*\(\d+\))?(?:\s+with(?:out)?\s+time\s+zone)?(?!\w)|time(?:\s+with(?:out)?\s+time\s+zone)?(?!\w)|[\w.]+)(?:\s*\([^)]*\))?(?:\s+unsigned)?(?:\s*\[\])?)", rest, re.I)
    ctype = re.sub(r"\s+", " ", tm.group(1).lower()) if tm else ""
    ru = rest.upper()
    col = {"name": name, "quoted": quoted, "type": ctype, "not_null": "NOT NULL" in ru or "PRIMARY KEY" in ru,
           "default": "DEFAULT" in ru or "IDENTITY" in ru or "AUTO_INCREMENT" in ru or ctype.endswith("serial"),
           "check": "CHECK" in ru}
    t["cols"][name.lower()] = col
    t["order"].append(name.lower())
    if "PRIMARY KEY" in ru:
        t["pk"] = [name.lower()]
    if re.search(r"\bUNIQUE\b", ru):
        t["uniques"].append([name.lower()])
        sc.indexes.append({"table": t["name"].lower(), "cols": [name.lower()], "unique": True, "name": "", "partial": False, "line": t["line"]})
    rm = re.search(r"REFERENCES\s+([\w\".`]+)\s*(?:\((.*?)\))?", rest, re.I)
    if rm:
        sc.fks.append({"table": t["name"].lower(), "cols": [name.lower()], "ref": ident(rm.group(1))[0].lower(),
                       "ref_cols": cols_list(rm.group(2)) if rm.group(2) else None})
    if col["check"]:
        checks.append(f"check ({name})")


def qi(name):
    return f'"{name}"' if name.lower() in RESERVED or name != name.lower() else name


def base_type(ctype):
    t = re.sub(r"\(.*?\)|\s+unsigned|\[\]", "", ctype).strip()
    return {"int4": "integer", "int": "integer", "serial": "integer", "serial4": "integer", "int8": "bigint",
            "bigserial": "bigint", "serial8": "bigint", "int2": "smallint", "smallserial": "smallint"}.get(t, t)


def lint(sql, dialect="auto", ignore=()):
    sc = parse(sql)
    if dialect == "auto":
        dialect = "mysql" if sc.dialect_hints["mysql"] > sc.dialect_hints["postgres"] else "postgres"
    out = []

    def add(*a, **k):
        f = finding(*a, **k)
        if f["code"] not in ignore:
            out.append(f)

    table_names = set(sc.tables)
    for key, t in sc.tables.items():
        tn = t["name"]
        ln = t["line"]
        if not t["pk"]:
            add("HIGH", "NO_PRIMARY_KEY", tn, "", "table has no primary key: duplicate rows cannot be told apart, updates and replication (logical replication, MySQL row-based, CDC) suffer",
                "add a bigint identity (or UUID) primary key, or a composite key on the natural unique columns", line=ln)
        elif len(t["pk"]) == 1 and t["pk"][0] in t["cols"]:
            c = t["cols"][t["pk"][0]]
            bt = base_type(c["type"])
            if bt in {"integer", "smallint", "mediumint", "tinyint"} and not re.search(r"(^|_)(type|status|kind|country|currency|lookup)s?$", tn, re.I):
                add("MEDIUM", "INT32_PRIMARY_KEY", tn, c["name"], f"primary key {c['name']} is {c['type']} (max about 2.1 billion, less for smaller types); running out means an emergency type change on the biggest table",
                    "use bigint GENERATED ALWAYS AS IDENTITY (Postgres) or BIGINT UNSIGNED AUTO_INCREMENT (MySQL)", line=ln)
        if dialect == "postgres" and t["quoted"] and t["name"] != t["name"].lower():
            add("LOW", "MIXED_CASE_NAME", tn, "", f'table "{tn}" is quoted mixed case: every query must quote it forever', "use snake_case lower-case names", line=ln)
        if tn.lower() in RESERVED and not (dialect == "postgres" and tn.lower() in RESERVED_PG_ONLY_SAFE) and not (dialect == "mysql" and tn.lower() in RESERVED_MY_ONLY_SAFE):
            add("MEDIUM", "RESERVED_WORD_NAME", tn, "", f"table name '{tn}' is a reserved word and must be quoted in every query and ORM", "rename (e.g. users, orders, user_groups)", line=ln)
        if dialect == "mysql":
            opts = t["options"].lower()
            if re.search(r"engine\s*=\s*myisam", opts):
                add("HIGH", "MYISAM_ENGINE", tn, "", "ENGINE=MyISAM has no transactions, no foreign keys and table-level locks; crashes can corrupt it", "use ENGINE=InnoDB", line=ln)
            if re.search(r"charset\s*=\s*utf8(mb3)?\b(?!mb4)", opts):
                add("MEDIUM", "MYSQL_UTF8MB3", tn, "", "utf8 in MySQL is 3-byte utf8mb3: emoji and some CJK characters fail to insert or get mangled", "use DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", line=ln)
        if not any(re.match(r"^(created_at|created|created_on|inserted_at|date_created|creation_date)$", c) for c in t["cols"]):
            add("LOW", "NO_CREATED_AT", tn, "", "no created_at column: hard to debug, audit or backfill later", "add created_at timestamptz NOT NULL DEFAULT now()", line=ln)
        v255 = [c["name"] for c in t["cols"].values() if re.match(r"(varchar|character varying)\s*\(255\)", c["type"])]
        if dialect == "postgres" and len(v255) >= 3:
            add("LOW", "VARCHAR_255_HABIT", tn, ", ".join(v255), f"{len(v255)} columns are varchar(255): in Postgres the limit costs nothing to drop but 255 is rarely the real rule",
                "use text, with a CHECK (char_length(x) <= n) where a real limit exists", line=ln)
        for cname in t["order"]:
            c = t["cols"][cname]
            ct, bt = c["type"], base_type(c["type"])
            cn = c["name"]
            if MONEY_RE.search(cn) and bt in {"float", "real", "double", "double precision", "float4", "float8"}:
                add("HIGH", "FLOAT_MONEY", tn, cn, f"{cn} is {ct}: binary floating point cannot store 0.10 exactly, sums drift by cents",
                    "use numeric(12,2) / DECIMAL(12,2), or bigint minor units (amount_cents)", line=ln)
            if bt == "money" and dialect == "postgres":
                add("MEDIUM", "MONEY_TYPE", tn, cn, "Postgres money type depends on lc_monetary, has one fixed currency and rounds", "use numeric(12,2) plus a currency column", line=ln)
            if dialect == "postgres" and (re.match(r"^timestamp(\s*\(\d+\))?$", ct) or "without time zone" in ct):
                add("MEDIUM", "TIMESTAMP_WITHOUT_TZ", tn, cn, f"{cn} is timestamp without time zone: the instant depends on whatever zone the writer assumed", "use timestamptz (stores an absolute instant, displays in the session zone)", line=ln)
            if dialect == "mysql" and bt == "datetime" and re.search(r"_at$", cn):
                add("LOW", "DATETIME_NO_ZONE", tn, cn, f"{cn} is DATETIME (no zone): make sure every writer stores UTC", "document and enforce UTC (time_zone='+00:00' on connections) or use TIMESTAMP within its 2038 range", line=ln)
            if re.match(r"^(created_at|updated_at|inserted_at)$", cn, re.I) and not c["not_null"]:
                add("MEDIUM", "NULLABLE_AUDIT_COLUMN", tn, cn, f"{cn} is nullable{'' if c['default'] else ' and has no default'}: rows without it will appear", f"{cn} timestamptz NOT NULL DEFAULT now()", line=ln)
            if bt in {"boolean", "bool"} and not c["not_null"]:
                add("LOW", "NULLABLE_BOOLEAN", tn, cn, f"{cn} is a nullable boolean: three states (true, false, unknown) and NULL-unsafe WHERE clauses", f"{cn} boolean NOT NULL DEFAULT false", line=ln)
            if STATUS_RE.match(cn) and re.match(r"^(text|varchar|character varying|char|character)", bt) and not c["check"] \
                    and cn.lower() not in t["checks"] and not any(f["table"] == key and cname in f["cols"] for f in sc.fks):
                add("LOW", "UNCHECKED_STATUS", tn, cn, f"{cn} is free text: typos like 'Shipped ' and 'shiped' will end up in the data", "add CHECK (status IN (...)), an enum type, or a FK to a lookup table", line=ln)
            if bt in {"text", "longtext", "mediumtext"} and JSONISH_RE.search(cn):
                add("LOW", "JSON_IN_TEXT", tn, cn, f"{cn} looks like JSON stored as {ct}: no validation, no indexing", "use jsonb (Postgres) or JSON (MySQL) if it really is JSON", line=ln)
            if cn.lower() in RESERVED and not (dialect == "postgres" and cn.lower() in RESERVED_PG_ONLY_SAFE) and not (dialect == "mysql" and cn.lower() in RESERVED_MY_ONLY_SAFE) and cn.lower() not in {"type"}:
                add("MEDIUM", "RESERVED_WORD_NAME", tn, cn, f"column name '{cn}' is a reserved word and needs quoting everywhere", "rename it (e.g. sort_order, user_id, group_name, ends_at)", line=ln)
            if dialect == "postgres" and c["quoted"] and cn != cn.lower():
                add("LOW", "MIXED_CASE_NAME", tn, cn, f'column "{cn}" is quoted mixed case: every query must quote it', "use snake_case", line=ln)
            if cn.lower().endswith("_id") and cname not in t["pk"] and not any(f["table"] == key and cname in f["cols"] for f in sc.fks):
                stem = cn.lower()[:-3]
                cands = [x for x in (stem, stem + "s", stem + "es", stem[:-1] + "ies" if stem.endswith("y") else None) if x and x in table_names]
                if cands:
                    add("LOW", "MISSING_FOREIGN_KEY", tn, cn, f"{cn} looks like a reference to {cands[0]} but has no foreign key: orphans and typos are possible", f"add REFERENCES {cands[0]}(id) (with an index)", line=ln)
            if re.search(r"(^|_)email$", cn, re.I) and [cname] in t["uniques"] and dialect == "postgres" and bt != "citext":
                if not any(i["table"] == key and any("lower(" in c2 for c2 in i["cols"]) for i in sc.indexes):
                    add("LOW", "CASE_SENSITIVE_UNIQUE_EMAIL", tn, cn, "UNIQUE on email is case-sensitive in Postgres: Ana@x.com and ana@x.com can both sign up", "CREATE UNIQUE INDEX ... ON t (lower(email)) or use citext", line=ln)
    # foreign keys: types and indexes
    for f in sc.fks:
        t = sc.tables.get(f["table"])
        r = sc.tables.get(f["ref"])
        if not t:
            continue
        ref_cols = f["ref_cols"] or (r["pk"] if r else None)
        if r and ref_cols and len(ref_cols) == len(f["cols"]):
            for c, rc in zip(f["cols"], ref_cols):
                a, b = t["cols"].get(c), r["cols"].get(rc)
                if a and b and base_type(a["type"]) != base_type(b["type"]) and not ({base_type(a["type"]), base_type(b["type"])} <= {"uuid"}):
                    add("HIGH", "FK_TYPE_MISMATCH", t["name"], a["name"], f"{a['name']} is {a['type']} but references {r['name']}.{b['name']} ({b['type']}): joins need casts and the FK fails once ids pass the smaller range",
                        f"make {a['name']} the same type as {r['name']}.{b['name']}", line=t["line"])
        if dialect == "postgres":
            covered = any(idx["table"] == f["table"] and not idx["partial"] and idx["cols"][:len(f["cols"])] == f["cols"] for idx in sc.indexes) \
                or t["pk"][:len(f["cols"])] == f["cols"] or any(u[:len(f["cols"])] == f["cols"] for u in t["uniques"])
            if not covered:
                add("MEDIUM", "FK_WITHOUT_INDEX", t["name"], ", ".join(f["cols"]), f"foreign key ({', '.join(f['cols'])}) -> {f['ref']} has no index starting with it: deletes/updates on {f['ref']} scan {t['name']}, and joins are slow",
                    f"CREATE INDEX CONCURRENTLY ON {qi(t['name'])} ({', '.join(f['cols'])})", line=t["line"])
    # redundant indexes
    for i, a in enumerate(sc.indexes):
        t = sc.tables.get(a["table"])
        if not t or a["partial"] or any("(" in c for c in a["cols"]):
            continue
        others = [b for j, b in enumerate(sc.indexes) if j != i and b["table"] == a["table"] and not b["partial"]]
        if t["pk"] and a["cols"] == t["pk"][:len(a["cols"])] and not a["unique"]:
            add("LOW", "REDUNDANT_INDEX", t["name"], ", ".join(a["cols"]), f"index on ({', '.join(a['cols'])}) duplicates the primary key's leading columns", "drop it", line=a["line"])
            continue
        for b in others:
            if len(b["cols"]) > len(a["cols"]) and b["cols"][:len(a["cols"])] == a["cols"] and not a["unique"]:
                add("LOW", "REDUNDANT_INDEX", t["name"], ", ".join(a["cols"]), f"index on ({', '.join(a['cols'])}) is a prefix of the index on ({', '.join(b['cols'])})", "drop the shorter one unless it is much smaller and hot", line=a["line"])
                break
            if b["cols"] == a["cols"] and j_before(sc.indexes, b, a) and a["unique"] == b["unique"]:
                add("LOW", "REDUNDANT_INDEX", t["name"], ", ".join(a["cols"]), f"two indexes on ({', '.join(a['cols'])})", "drop one", line=a["line"])
                break
    out.sort(key=lambda f: (SEV_ORDER[f["severity"]], f["table"], f["column"], f["code"]))
    return dialect, sc, out


def j_before(lst, b, a):
    return lst.index(b) < lst.index(a)


def report(path, dialect, sc, found):
    counts = {s: sum(1 for f in found if f["severity"] == s) for s in SEV_ORDER}
    out = [f"# Schema review: {path} ({dialect})", "",
           f"Tables: {len(sc.tables)}   Indexes: {len(sc.indexes)}   Foreign keys: {len(sc.fks)}   Findings: {len(found)} (HIGH {counts['HIGH']}, MEDIUM {counts['MEDIUM']}, LOW {counts['LOW']})", ""]
    if not found:
        out.append("No findings.")
        return "\n".join(out)
    out += ["| Sev | Code | Table.Column | Problem | Fix |", "|---|---|---|---|---|"]
    for f in found:
        loc = f["table"] + ("." + f["column"] if f["column"] else "")
        out.append(f"| {f['severity']} | {f['code']} | {loc} | {f['problem'].replace('|', '/')} | {f['fix'].replace('|', '/')} |")
    return "\n".join(out)


def self_test():
    ok_pk = "CREATE TABLE t (id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY, created_at timestamptz NOT NULL DEFAULT now()"
    cases = [
        ("clean postgres table", ok_pk + ", name text NOT NULL);", "postgres", [], ["NO_PRIMARY_KEY", "INT32_PRIMARY_KEY", "NO_CREATED_AT"]),
        ("no primary key", "CREATE TABLE logs (msg text, created_at timestamptz NOT NULL);", "auto", ["NO_PRIMARY_KEY"], []),
        ("table-level composite pk", "CREATE TABLE m (a bigint, b bigint, created_at timestamptz NOT NULL, PRIMARY KEY (a, b));", "auto", [], ["NO_PRIMARY_KEY"]),
        ("named pk constraint", "CREATE TABLE m (id bigint, created_at timestamptz NOT NULL, CONSTRAINT m_pk PRIMARY KEY (id));", "auto", [], ["NO_PRIMARY_KEY"]),
        ("pk added by alter", "CREATE TABLE m (id bigint NOT NULL, created_at timestamptz NOT NULL); ALTER TABLE m ADD CONSTRAINT m_pkey PRIMARY KEY (id);", "auto", [], ["NO_PRIMARY_KEY"]),
        ("serial pk is int32", "CREATE TABLE orders (id serial PRIMARY KEY, created_at timestamptz NOT NULL);", "auto", ["INT32_PRIMARY_KEY"], []),
        ("small lookup table int pk ok", "CREATE TABLE order_status (id smallint PRIMARY KEY, created_at timestamptz NOT NULL);", "auto", [], ["INT32_PRIMARY_KEY"]),
        ("float money", ok_pk + ", total_price double precision);", "postgres", ["FLOAT_MONEY"], []),
        ("numeric money ok", ok_pk + ", amount numeric(12,2) NOT NULL);", "postgres", [], ["FLOAT_MONEY"]),
        ("float non-money ok", ok_pk + ", latitude double precision);", "postgres", [], ["FLOAT_MONEY"]),
        ("money type", ok_pk + ", balance money);", "postgres", ["MONEY_TYPE"], []),
        ("timestamp without tz", ok_pk + ", shipped_at timestamp);", "postgres", ["TIMESTAMP_WITHOUT_TZ"], []),
        ("timestamp(3) without time zone", ok_pk + ", shipped_at timestamp(3) without time zone);", "postgres", ["TIMESTAMP_WITHOUT_TZ"], []),
        ("timestamptz ok", ok_pk + ", shipped_at timestamp with time zone);", "postgres", [], ["TIMESTAMP_WITHOUT_TZ"]),
        ("nullable created_at", "CREATE TABLE t (id bigint PRIMARY KEY, created_at timestamptz);", "postgres", ["NULLABLE_AUDIT_COLUMN"], []),
        ("no created_at", "CREATE TABLE t (id bigint PRIMARY KEY, name text);", "postgres", ["NO_CREATED_AT"], []),
        ("nullable boolean", ok_pk + ", is_active boolean);", "postgres", ["NULLABLE_BOOLEAN"], []),
        ("boolean not null ok", ok_pk + ", is_active boolean NOT NULL DEFAULT true);", "postgres", [], ["NULLABLE_BOOLEAN"]),
        ("unchecked status", ok_pk + ", status varchar(20) NOT NULL);", "postgres", ["UNCHECKED_STATUS"], []),
        ("status with check ok", ok_pk + ", status text NOT NULL CHECK (status IN ('a','b')));", "postgres", [], ["UNCHECKED_STATUS"]),
        ("status table check ok", ok_pk + ", status text NOT NULL, CONSTRAINT st CHECK (status IN ('a')));", "postgres", [], ["UNCHECKED_STATUS"]),
        ("reserved table name", "CREATE TABLE \"user\" (id bigint PRIMARY KEY, created_at timestamptz NOT NULL);", "postgres", ["RESERVED_WORD_NAME"], []),
        ("reserved column order", ok_pk + ", \"order\" int);", "postgres", ["RESERVED_WORD_NAME"], []),
        ("mixed case quoted", "CREATE TABLE \"OrderItems\" (id bigint PRIMARY KEY, created_at timestamptz NOT NULL);", "postgres", ["MIXED_CASE_NAME"], []),
        ("fk without index", "CREATE TABLE a (id bigint PRIMARY KEY, created_at timestamptz NOT NULL); CREATE TABLE b (id bigint PRIMARY KEY, created_at timestamptz NOT NULL, a_id bigint NOT NULL REFERENCES a(id));", "postgres", ["FK_WITHOUT_INDEX"], ["FK_TYPE_MISMATCH"]),
        ("fk with index ok", "CREATE TABLE a (id bigint PRIMARY KEY, created_at timestamptz NOT NULL); CREATE TABLE b (id bigint PRIMARY KEY, created_at timestamptz NOT NULL, a_id bigint REFERENCES a); CREATE INDEX ON b (a_id, id);", "postgres", [], ["FK_WITHOUT_INDEX"]),
        ("fk covered by composite pk", "CREATE TABLE a (id bigint PRIMARY KEY, created_at timestamptz NOT NULL); CREATE TABLE ab (a_id bigint REFERENCES a(id), x bigint, created_at timestamptz NOT NULL, PRIMARY KEY (a_id, x));", "postgres", [], ["FK_WITHOUT_INDEX"]),
        ("fk type mismatch", "CREATE TABLE a (id bigint PRIMARY KEY, created_at timestamptz NOT NULL); CREATE TABLE b (id bigint PRIMARY KEY, created_at timestamptz NOT NULL, a_id integer, FOREIGN KEY (a_id) REFERENCES a (id));", "postgres", ["FK_TYPE_MISMATCH"], []),
        ("missing fk on _id", "CREATE TABLE customers (id bigint PRIMARY KEY, created_at timestamptz NOT NULL); CREATE TABLE orders (id bigint PRIMARY KEY, created_at timestamptz NOT NULL, customer_id bigint NOT NULL);", "postgres", ["MISSING_FOREIGN_KEY"], []),
        ("external _id without table ok", ok_pk + ", stripe_id text);", "postgres", [], ["MISSING_FOREIGN_KEY"]),
        ("case-sensitive unique email", ok_pk + ", email text NOT NULL UNIQUE);", "postgres", ["CASE_SENSITIVE_UNIQUE_EMAIL"], []),
        ("lower(email) index ok", ok_pk + ", email text NOT NULL UNIQUE); CREATE UNIQUE INDEX t_email ON t (lower(email));", "postgres", [], ["CASE_SENSITIVE_UNIQUE_EMAIL"]),
        ("redundant prefix index", ok_pk + ", a bigint, b bigint); CREATE INDEX i1 ON t (a); CREATE INDEX i2 ON t (a, b);", "postgres", ["REDUNDANT_INDEX"], []),
        ("json in text", ok_pk + ", payload text);", "postgres", ["JSON_IN_TEXT"], []),
        ("varchar 255 habit", ok_pk + ", a varchar(255), b varchar(255), c varchar(255));", "postgres", ["VARCHAR_255_HABIT"], []),
        ("mysql myisam and utf8", "CREATE TABLE `t` (`id` int unsigned NOT NULL AUTO_INCREMENT, `created_at` datetime NOT NULL, PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8;", "auto", ["MYISAM_ENGINE", "MYSQL_UTF8MB3", "INT32_PRIMARY_KEY", "DATETIME_NO_ZONE"], ["TIMESTAMP_WITHOUT_TZ"]),
        ("mysql utf8mb4 innodb ok", "CREATE TABLE `t` (`id` bigint unsigned NOT NULL AUTO_INCREMENT, `created_at` datetime NOT NULL, PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;", "auto", [], ["MYISAM_ENGINE", "MYSQL_UTF8MB3", "INT32_PRIMARY_KEY"]),
        ("mysql fk needs no extra index", "CREATE TABLE a (id bigint PRIMARY KEY, created_at datetime NOT NULL) ENGINE=InnoDB; CREATE TABLE b (id bigint PRIMARY KEY, created_at datetime NOT NULL, a_id bigint, FOREIGN KEY (a_id) REFERENCES a(id)) ENGINE=InnoDB;", "mysql", [], ["FK_WITHOUT_INDEX"]),
        ("comments and strings ignored", "-- CREATE TABLE x (a int);\n/* CREATE TABLE y (b int); */\n" + ok_pk + ", note text DEFAULT 'a;b -- c');", "postgres", [], ["NO_PRIMARY_KEY"]),
        ("alter add column parsed", ok_pk + "); ALTER TABLE t ADD COLUMN total_amount float;", "postgres", ["FLOAT_MONEY"], []),
    ]
    passed = 0
    for name, sql, dialect, expect, absent in cases:
        d, sc, found = lint(sql, dialect)
        codes = {f["code"] for f in found}
        ok = all(c in codes for c in expect) and not any(c in codes for c in absent)
        if name == "clean postgres table":
            ok = ok and not found
        if name == "comments and strings ignored":
            ok = ok and len(sc.tables) == 1
        if name.startswith("mysql myisam"):
            ok = ok and d == "mysql"
        passed += ok
        print(("PASS " if ok else "FAIL ") + name + ("" if ok else f" -> got {sorted(codes)}"))
    d, sc, found = lint("", "auto")
    ok = report("x.sql", d, sc, found).endswith("No findings.")
    passed += ok
    print(("PASS " if ok else "FAIL ") + "empty report")
    total = len(cases) + 1
    print(f"{passed}/{total} passed")
    return 0 if passed == total else 1


def main(argv=None):
    ap = argparse.ArgumentParser(description="SQL schema design linter (Postgres/MySQL DDL)")
    ap.add_argument("files", nargs="*")
    ap.add_argument("--dialect", default="auto", choices=["auto", "postgres", "mysql"])
    ap.add_argument("--min-severity", default="LOW", choices=list(SEV_ORDER))
    ap.add_argument("--ignore", default="")
    ap.add_argument("--json", action="store_true")
    ap.add_argument("--self-test", action="store_true")
    a = ap.parse_args(argv)
    if a.self_test:
        return self_test()
    if not a.files:
        ap.print_usage(sys.stderr)
        return 2
    ignore = {c.strip() for c in a.ignore.split(",") if c.strip()}
    sql_all = []
    for p in a.files:
        try:
            with open(p, encoding="utf-8") as fh:
                sql_all.append(fh.read())
        except OSError as e:
            print(f"error: cannot read {p}: {e}", file=sys.stderr)
            return 2
    dialect, sc, found = lint("\n;\n".join(sql_all), a.dialect, ignore)
    if not sc.tables:
        print("error: no CREATE TABLE statements found", file=sys.stderr)
        return 2
    found = [f for f in found if SEV_ORDER[f["severity"]] <= SEV_ORDER[a.min_severity]]
    if a.json:
        print(json.dumps({"dialect": dialect, "tables": len(sc.tables), "findings": found}, indent=2))
    else:
        print(report(", ".join(a.files), dialect, sc, found))
    return 1 if any(f["severity"] == "HIGH" for f in found) else 0


if __name__ == "__main__":
    sys.exit(main())
Prompts
