Darling Data — Claude Code plugins

A Claude Code plugin marketplace from Darling Data.

/plugin marketplace add erikdarlingdata/claude-plugins

Plugins

sqlserver-query-plans

Teaches Claude to read a SQL Server execution plan and say what is actually slow, and why.

/plugin install sqlserver-query-plans@erikdarling

Point Claude at a .sqlplan file and ask. The skill is model-invoked — you do not need to call it explicitly.

The hard part of plan analysis is not spotting operators. It is knowing which numbers mean what they appear to mean. This plugin is built mostly out of the conclusions that sound authoritative and are wrong:

• Cost percentages are estimates in every plan, including actual plans. Nothing recomputes them after execution. The 97%-cost operator is routinely not the slow one, and an operator shown at 0% can consume the entire runtime.
• Row-mode operator times are cumulative. Ranking operators by raw ActualElapsedms ranks them by depth and always crowns the root node. Batch mode reports standalone times. Exchange operators report times that are close to meaningless.
• EstimateRows is per-execution; ActualRows is a total. Without dividing by ActualExecutions, the inner side of every nested loop looks catastrophically underestimated when it may have estimated perfectly.
• Missing-index requests are hints, not DDL. Equality columns come out in arbitrary order, existing indexes are ignored, and the Impact figure is a percentage of an estimated cost.
• A scan is not a defect and a seek is not a virtue. Judge by rows touched and time spent.

It also ships scripts/extract.py, which flattens a .sqlplan into a compact digest. This is not a convenience:

• .sqlplan files are UTF-16, so grep silently matches nothing and reports no error. A negative result from grep on a plan file is worthless.
• Some plans are UTF-8 bytes that still declare encoding="utf-16", because they were opened and re-saved. Strict XML parsers reject them.
• A trivial two-table join is 120 KB. Real plans run to megabytes. Reading one into context wastes the context and still misses things.

The extractor handles the encoding, computes correct self-time attribution (subtracting children in row mode, within a thread rather than across threads in parallel plans, and not at all in batch mode), normalizes cardinality per execution, and recognizes the optimizer's default-guess selectivity fingerprints. --node N drills into a single operator; --sql recovers full statement text.

Requires Python 3 (standard library only). Without it, the skill degrades to a documented grep-based fallback and says plainly what it cannot determine.

GitHub Copilot CLI

This plugin also works in GitHub Copilot CLI, which reads the same SKILL.md and plugin.json format.

copilot plugin marketplace add erikdarlingdata/claude-plugins
copilot plugin install sqlserver-query-plans@erikdarling

Or add just the skill, without the marketplace:

/skills add ./plugins/sqlserver-query-plans/skills/query-plan-analysis

As in Claude Code, the skill is model-invoked: point Copilot at a .sqlplan and ask.

About

Built by Erik Darling at Darling Data. SQL Server consulting, training, and free tools: https://erikdarling.com

License

MIT