Feature: EXPLAIN ANALYZE visual query plan viewer

[muk2]

Overview

Parse EXPLAIN ANALYZE output and render it as a visual tree in the TUI, with color-coded cost annotations and timing breakdowns, making query optimization intuitive.

Goals

• Visual tree rendering of query execution plans
• Color-coded cost/timing annotations (green = fast, red = slow)
• Identify bottleneck nodes at a glance
• Support both EXPLAIN and EXPLAIN ANALYZE output

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Proposed Behavior

Activation

• When a query starts with EXPLAIN or EXPLAIN ANALYZE, parse the output into a visual plan instead of showing raw text
• Toggle between raw text and visual plan with a keybinding (e.g., Ctrl+E)

Visual Plan Rendering

Query Plan (total: 245.32ms)
├─ Nested Loop (cost=0.71..28.53 rows=10) [actual: 2.1ms]
│  ├─ Index Scan on users_pkey (cost=0.29..8.30) [actual: 0.3ms] ✓
│  │     Index Cond: (id = $1)
│  └─ Index Scan on orders_user_id_idx (cost=0.42..2.02) [actual: 1.8ms] ✓
│        Index Cond: (user_id = users.id)
│        Filter: (status = 'active')
│        Rows Removed by Filter: 3
└─ Sort (cost=12.00..12.25 rows=10) [actual: 0.1ms] ✓
      Sort Key: orders.created_at DESC
      Sort Method: quicksort Memory: 25kB

Color Coding

Color	Meaning
Green	Fast node (< 10% of total time)
Yellow	Moderate (10-30% of total time)
Red	Slow / bottleneck (> 30% of total time)
Cyan	Index usage

Information Displayed

• Node type (Seq Scan, Index Scan, Hash Join, etc.)
• Estimated vs actual rows (highlight large discrepancies)
• Cost range
• Actual execution time (from ANALYZE)
• Filter conditions and rows removed
• Sort methods and memory usage
• I/O timing (if available via EXPLAIN (ANALYZE, BUFFERS))

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Implementation Suggestions

• Parse the text output of EXPLAIN (FORMAT TEXT) line by line
• Build a tree structure from indentation levels
• Alternatively, use EXPLAIN (FORMAT JSON) for structured parsing
• Render using ratatui's Paragraph with styled spans
• Add a PlanNode struct: { node_type, cost, actual_time, rows_est, rows_actual, children, details }
• Detect EXPLAIN queries in execute_query() and auto-switch to plan view

Definition of Done

• EXPLAIN output is parsed into a tree structure
• Visual tree renders in the results pane
• Nodes are color-coded by relative cost
• Both EXPLAIN and EXPLAIN ANALYZE are supported
• Toggle between raw and visual view
• Large discrepancies between estimated/actual rows are highlighted