# Postgis Query Patterns

> Use when writing PostGIS or spatial SQL — distance, proximity, intersection, or geometry storage queries. Makes the agent use correct SRIDs, spatial indexes, and the right ST_ functions, so spatial SQL is both correct and fast instead of silently slow or wrong.

- **Type:** Skill
- **Install:** `agentstack add skill-buildmoonshot-skillpacks-postgis-query-patterns`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [buildmoonshot](https://agentstack.voostack.com/s/buildmoonshot)
- **Installs:** 0
- **Category:** [Databases](https://agentstack.voostack.com/c/databases)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [buildmoonshot](https://github.com/buildmoonshot)
- **Source:** https://github.com/buildmoonshot/skillpacks/tree/main/skills/gis/intermediate/postgis-query-patterns

## Install

```sh
agentstack add skill-buildmoonshot-skillpacks-postgis-query-patterns
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# PostGIS Query Patterns

PostGIS rewards correct spatial SQL and quietly punishes the rest with wrong answers or full table scans. Follow the patterns.

## Storage & SRID

- Store geometry with a known SRID (typmod like `geometry(Point, 4326)` or `ST_SetSRID`). Operations between different SRIDs error or mislead — `ST_Transform` to align.
- Choose **`geography`** for accurate distances over large/global areas (meters on a sphere); **`geometry`** in an appropriate projected CRS for fast planar math.

## Make queries use the index

- Put a **GiST index** on every geometry column you query.
- Use index-assisted operators/functions: `&&`, `ST_Intersects`, `ST_DWithin`. These hit the index.
- **Avoid `ST_Distance(a, b) < x` in a WHERE clause** — it can't use the index and forces a full scan. Use `ST_DWithin(a, b, x)` instead.

## Correctness gotchas

- `&&` is **bounding-box only** — fast but approximate. Use it as a prefilter, then `ST_Intersects` for the exact test.
- Validate geometry before overlays (`ST_IsValid` / `ST_MakeValid`) — see `validate-geometry`.
- `ST_DWithin` distance units follow the type: meters for `geography`, CRS units for `geometry` (degrees if you left it in 4326 — usually not what you want for a distance).

## Why this matters

Spatial SQL fails quietly in two directions: wrong SRID or wrong function gives a confident wrong answer, and a missing index turns a sub-second query into a minutes-long table scan that still "works" in testing and falls over in production. The patterns above keep queries both correct and fast.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [buildmoonshot](https://github.com/buildmoonshot)
- **Source:** [buildmoonshot/skillpacks](https://github.com/buildmoonshot/skillpacks)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-buildmoonshot-skillpacks-postgis-query-patterns
- Seller: https://agentstack.voostack.com/s/buildmoonshot
- Browse the marketplace: https://agentstack.voostack.com/browse

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