Show query plans in the Linux SQL editor #3655

Problem

The Linux app has no way to show a query plan. The user can type EXPLAIN in the editor and read the plan as rows of text, but nothing draws it, and each engine has its own format: text or JSON on PostgreSQL and MySQL, XML on SQL Server, a list of steps on SQLite. The only EXPLAIN in the code is a unit test (linux/crates/core/src/statement/statement_builder.rs:166).

It is not on the roadmap: neither the backlog nor the Ideas list (linux/ROADMAP.md, Backlog, Ideas) mentions it. The macOS app draws plans (features/explain-visualization.mdx).

Proposed solution

• Explain in the editor, for the statement at the cursor or the selection, with a shortcut.
• Each engine runs its own form: EXPLAIN (FORMAT JSON) on PostgreSQL, EXPLAIN FORMAT=JSON on MySQL and MariaDB, SET SHOWPLAN_XML ON on SQL Server, EXPLAIN on ClickHouse, and EXPLAIN QUERY PLAN on SQLite.
• The plan shows as a tree of nodes in a results entry, built from GTK list widgets, with each node's estimated rows and cost where the engine gives them, and the costliest node marked.
• Explain Analyze, where the engine has it, runs the statement, so it asks first. On a statement that writes, it is refused on a read-only connection and otherwise runs inside a transaction that is rolled back.
• The raw plan text stays one click away, for copying.

Done means: on PostgreSQL, Explain on a join shows a tree with row estimates, and the same action works on the other engines with their own plan formats.

Alternatives considered

Run EXPLAIN by hand in the editor and read the rows.

Platform

Linux

Related database type

N/A / General