# design-postgis-tables

A reference for designing PostGIS spatial tables: geometry types, coordinate systems, spatial indexes and query patterns. Useful when you are laying out a schema for location data.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 344 installs · ★ 1874
- Author: tigerdata
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/timescale/pg-aiguide/tree/HEAD/skills/design-postgis-tables/SKILL.md
- Updated: 2026-10-22
- HTML: https://affpapa.org/en/nevibecode/skills/design-postgis-tables

## What it does

The skill answers the questions that usually show up after the first migration: GEOMETRY or GEOGRAPHY, which SRID, where does the index go. Inside there is a walkthrough of geometry types (POINT, LINESTRING, POLYGON plus their Z and M variants), a table of common SRIDs, and a side-by-side of GEOMETRY and GEOGRAPHY covering distance accuracy and function support.

It opens with five questions: geographic scope, primary query patterns, units for distance and area, expected scale, and whether you need a third coordinate. Then come the rules — use PostGIS types instead of PostgreSQL's built-in geometric types, always specify an SRID, put a GiST index on every geometry column. BRIN shows up as an option for large GEOMETRY tables where rows are naturally ordered on disk and coarser filtering is acceptable.

You need PostgreSQL 15+ with the PostGIS extension. The text also flags SQL injection: pass user-supplied values (WKT/WKB, coordinates, radii) as parameterized queries, and quote or whitelist dynamic identifiers. That warning alone is worth reading before you wire coordinates into a query string.

## Requirements
- Works with: PostgreSQL

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add timescale/pg-aiguide --skill design-postgis-tables -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/design-postgis-tables/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/design-postgis-tables/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add timescale/pg-aiguide --skill design-postgis-tables -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/design-postgis-tables/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add timescale/pg-aiguide --skill design-postgis-tables -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/design-postgis-tables/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install timescale/pg-aiguide design-postgis-tables
```

2. **Manually: put the files in place**
- File: `.github/skills/design-postgis-tables/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add timescale/pg-aiguide --skill design-postgis-tables -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/timescale/pg-aiguide --path skills/design-postgis-tables
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/design-postgis-tables/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add timescale/pg-aiguide --skill design-postgis-tables -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/timescale/pg-aiguide/tree/HEAD/skills/design-postgis-tables/SKILL.md

## When to use it
- pick between GEOMETRY and GEOGRAPHY for a table of coordinates
- set the SRID and geometry type in a column definition
- add a spatial index for radius and bbox queries
- compute distance and area in meters instead of degrees
- handle Z and M coordinates for tracks and linear referencing

## Example prompts
- Design a table for delivery points across the US, tell me the geometry type and SRID
- I need within-radius and nearest-neighbor queries — which indexes should I create?
- Review my schema with a geometry(POLYGON, 4326) column and suggest fixes

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 5a7a7fd763751a15.

BEGIN THIRD-PARTY FILE 5a7a7fd763751a15
````text
---
name: design-postgis-tables
description: Comprehensive PostGIS spatial table design reference covering geometry types, coordinate systems, spatial indexing, and performance patterns for location-based applications
license: Apache-2.0
compatibility: Requires PostgreSQL 15+ with the PostGIS extension
metadata:
  author: tigerdata
---

# PostGIS Spatial Table Design

## Before You Start (5 Questions)

1. What is the geographic scope (single city/region vs global)?
2. What are your primary query patterns (within-radius, bbox, intersects, nearest-neighbor)?
3. What units do you need for distance/area (meters vs CRS units), and how accurate must they be?
4. What is the expected scale (rows, write rate), and is the data mostly append-only?
5. Do you need 3D (Z) or measures (M), or is 2D enough?

**SQL injection note:** When turning these patterns into application code, use parameterized queries for user-provided values (WKT/WKB, coordinates, IDs, radii). Avoid string-concatenating untrusted input into SQL; for dynamic identifiers, use safe identifier quoting/whitelisting.

## Core Rules

- **Always use PostGIS geometry/geography types** instead of PostgreSQL's built-in geometric types (`POINT`, `LINE`, `POLYGON`, `CIRCLE`). PostGIS types provide true spatial capabilities.
- **Choose between GEOMETRY and GEOGRAPHY** based on your use case: GEOMETRY for projected/local data with Cartesian math; GEOGRAPHY for global data requiring accurate spherical calculations.
- **Always specify SRID** (Spatial Reference Identifier) when creating geometry columns. Use `4326` (WGS84) for GPS/global data, appropriate local projections for regional data.
- **Create spatial indexes** on all geometry/geography columns using GiST (default). Consider BRIN only for very large **GEOMETRY** tables where rows are naturally ordered on disk and you can tolerate coarser filtering.
- **Use constraint-based type enforcement** with `GEOMETRY(type, SRID)` syntax to ensure data integrity.

## Geometry vs Geography

### When to Use GEOMETRY

- **Local/regional data** within a single coordinate system
- **Projected coordinates** (meters, feet) for accurate area/distance calculations
- **Complex spatial operations** (buffering, unions, intersections)
- **Performance-critical queries** (Cartesian math is faster)
- **Data already in a projected CRS** (UTM, State Plane, etc.)

```sql
````
END THIRD-PARTY FILE 5a7a7fd763751a15

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