sql-tap

sql-tap

Real-time SQL traffic viewer — proxy daemon + TUI / Web client.

sql-tap sits between your application and your database (PostgreSQL, MySQL, or TiDB), capturing every query and displaying it in an interactive terminal UI. Inspect queries, view transactions, and run EXPLAIN — all without changing your application code.

Installation

Homebrew

brew install mickamy/tap/sql-tap

Go

go install github.com/mickamy/sql-tap@latest
go install github.com/mickamy/sql-tap/cmd/sql-tapd@latest

Build from source

git clone https://github.com/mickamy/sql-tap.git
cd sql-tap
make install

Docker

PostgreSQL

FROM postgres:18-alpine
ARG SQL_TAP_VERSION=0.0.1
ARG TARGETARCH
ADD https://github.com/mickamy/sql-tap/releases/download/v${SQL_TAP_VERSION}/sql-tap_${SQL_TAP_VERSION}_linux_${TARGETARCH}.tar.gz /tmp/sql-tap.tar.gz
RUN tar -xzf /tmp/sql-tap.tar.gz -C /usr/local/bin sql-tapd && rm /tmp/sql-tap.tar.gz
ENTRYPOINT ["sql-tapd", "--driver=postgres", "--listen=:5433", "--upstream=localhost:5432", "--grpc=:9091"]

MySQL

FROM mysql:8
ARG SQL_TAP_VERSION=0.0.1
ARG TARGETARCH
ADD https://github.com/mickamy/sql-tap/releases/download/v${SQL_TAP_VERSION}/sql-tap_${SQL_TAP_VERSION}_linux_${TARGETARCH}.tar.gz /tmp/sql-tap.tar.gz
RUN tar -xzf /tmp/sql-tap.tar.gz -C /usr/local/bin sql-tapd && rm /tmp/sql-tap.tar.gz
ENTRYPOINT ["sql-tapd", "--driver=mysql", "--listen=:3307", "--upstream=localhost:3306", "--grpc=:9091"]

Quick start

1. Start the proxy daemon

# PostgreSQL: proxy listens on :5433, forwards to PostgreSQL on :5432
DATABASE_URL="postgres://user:pass@localhost:5432/db?sslmode=disable" \
  sql-tapd --driver=postgres --listen=:5433 --upstream=localhost:5432

# MySQL: proxy listens on :3307, forwards to MySQL on :3306
DATABASE_URL="user:pass@tcp(localhost:3306)/db" \
  sql-tapd --driver=mysql --listen=:3307 --upstream=localhost:3306

# TiDB: proxy listens on :4001, forwards to TiDB on :4000
DATABASE_URL="user:pass@tcp(localhost:4000)/db" \
  sql-tapd --driver=tidb --listen=:4001 --upstream=localhost:4000

2. Point your application at the proxy

Connect your app to the proxy port instead of the database port. No code changes needed — sql-tapd speaks the native wire protocol.

3. Launch the TUI

sql-tap localhost:9091

All queries flowing through the proxy appear in real-time.

Usage

sql-tapd

sql-tapd — SQL proxy daemon for sql-tap

Usage:
  sql-tapd [flags]

Flags:
  -driver    database driver: postgres, mysql, tidb (required)
  -listen    client listen address (required)
  -upstream  upstream database address (required)
  -grpc      gRPC server address for TUI (default: ":9091")
  -http      HTTP server address for web UI (e.g. ":8080")
  -dsn-env   env var holding DSN for EXPLAIN (default: "DATABASE_URL")
  -nplus1-threshold  N+1 detection threshold (default: 5, 0 to disable)
  -nplus1-window     N+1 detection time window (default: 1s)
  -nplus1-cooldown   N+1 alert cooldown per query template (default: 10s)
  -version   show version and exit

Set DATABASE_URL (or the env var specified by -dsn-env) to enable EXPLAIN support. Without it, the proxy still captures queries but EXPLAIN is disabled.

Web UI

Add --http=:8080 to serve a browser-based viewer:

DATABASE_URL="postgres://user:pass@localhost:5432/db?sslmode=disable" \
  sql-tapd --driver=postgres --listen=:5433 --upstream=localhost:5432 --http=:8080

Open http://localhost:8080 in your browser to view queries in real-time. The web UI supports:

• Real-time query stream via SSE
• Click to inspect query details
• EXPLAIN / EXPLAIN ANALYZE
• Text filter
• Copy query (with or without bound args)
• N+1 detection (toast + row highlight)

sql-tap

sql-tap — Watch SQL traffic in real-time

Usage:
  sql-tap [flags] <addr>

Flags:
  -version  Show version and exit

<addr> is the gRPC address of sql-tapd (e.g. localhost:9091).

Keybindings

List view

Inspector view

Analytics view

Explain view

Filter syntax

Press f in the list view to enter filter mode. Filters support structured conditions that go beyond simple text search.

Multiple tokens are separated by spaces and combined with AND logic:

op:select d>100ms

This shows only SELECT queries that took longer than 100ms.

Both / (text search) and f (filter) can be active simultaneously — the filter is applied first, then the text search narrows the results further.

N+1 query detection

sql-tap automatically detects N+1 query patterns — when the same SELECT template is executed many times in a short time window.

Detection is enabled by default and runs server-side, so both TUI and Web UI benefit:

• TUI: alert overlay on first detection + N+1 marker in the Status column for every flagged query
• Web UI: toast notification on first detection + yellow row highlight + N+1 in the Status column

Configuration

Only SELECT queries are monitored. INSERT, UPDATE, DELETE, and transaction lifecycle commands (BEGIN, COMMIT, etc.) are excluded.

Once the threshold is crossed, all subsequent executions of the same template within the window are flagged. The cooldown only affects the notification frequency — the Status column marker always appears.

To disable detection entirely:

sql-tapd --nplus1-threshold=0 ...

Known limitations

Arrow key input in search / filter mode

Due to a limitation in the terminal input parser used by Bubble Tea v1, multi-byte escape sequences (such as arrow keys: ESC [ A/B/C/D) can occasionally be split across OS-level read() calls. When this happens, the remaining bytes ([A, [B, [C, [D, [F, [H) would appear as garbage text in the input field.

sql-tap includes a workaround that detects and discards these split sequences. As a side effect, the literal two-character strings [A, [B, [C, [D, [F, and [H cannot be typed in search or filter input. This is unlikely to affect real-world usage since these patterns rarely appear in SQL queries.

How it works

┌─────────────┐      ┌───────────────────────┐      ┌───────────────────────────┐
│ Application │─────▶│  sql-tapd (proxy)     │─────▶│ PostgreSQL / MySQL / TiDB │
└─────────────┘      │                       │      └───────────────────────────┘
                     │  captures queries     │
                     │  via wire protocol    │
                     └───────────┬───────────┘
                                 │ gRPC stream / SSE
                     ┌───────────▼───────────┐
                     │  sql-tap (TUI)        │
                     │  Browser  (Web UI)    │
                     └───────────────────────┘

sql-tapd parses the database wire protocol (PostgreSQL, MySQL, or TiDB) to intercept queries transparently. It tracks prepared statements, parameter bindings, transactions, execution time, rows affected, and errors. Events are streamed to connected TUI clients via gRPC.

See also

• grpc-tap — Same concept for gRPC. Transparent HTTP/2 reverse proxy that captures every gRPC / gRPC-Web / Connect call with TUI + Web UI.

License

MIT