{ "openapi": "3.1.1", "info": { "title": "Query Plan Visualizer API", "version": "1.0.0", "summary": "PostgreSQL EXPLAIN (ANALYZE) or MySQL EXPLAIN JSON → plan tree, hot nodes and index suggestions.", "description": "Every endpoint performs the same calculation as the human page and returns inputs, result, units, assumptions, sources, warnings and computedAt. MCP endpoint: /mcp." }, "servers": [ { "url": "https://queryplanvisualizer.usefulweb.site" } ], "paths": { "/api/v1/calculate": { "post": { "operationId": "calculate", "summary": "PostgreSQL EXPLAIN (ANALYZE) or MySQL EXPLAIN JSON → plan tree, hot nodes and index suggestions.", "description": "Paste PostgreSQL EXPLAIN / EXPLAIN ANALYZE output (text or FORMAT JSON) or MySQL EXPLAIN FORMAT=JSON. The plan is drawn as a node tree with cost, estimated vs actual rows, inclusive and exclusive time per node, and checked for the classic problems: row misestimates, sequential scans that discard most rows, sorts and hashes spilling to disk, nested loops over large inputs — each with a concrete fix such as a specific CREATE INDEX statement or work_mem setting.\n\nMethodology:\n- PostgreSQL text plans are parsed by the \"->\" indentation; node headers give cost=startup..total rows width and (actual time=startup..total rows loops); detail lines (Filter, Rows Removed by Filter, Sort Method, Buckets/Batches, Buffers…) are mapped to the same keys as FORMAT JSON.\n- Actual time and rows are per-loop averages (PostgreSQL docs), so inclusive time = actual total time × loops; exclusive time = inclusive − children's inclusive time. Under Gather, time is divided by the number of participating processes.\n- Misestimate = max(estimated, actual)/min(…) rows per loop at or above the threshold (and ≥100 rows absolute difference).\n- Rules: Seq Scan with Filter removing ≥90% of ≥1000 rows; Index Scan still filtering; Sort Method external/Disk; Hash Batches > 1; Nested Loop with ≥1000 outer rows and a sequential inner side or ≥10k inner loops; lossy bitmaps; workers not launched; heap fetches in index-only scans.\n- Index candidates take equality-compared filter columns first, then the first range column (B-tree column-order rule); functions in filters call for expression indexes and leading-wildcard LIKE for pg_trgm.\n- MySQL: access_type ALL / index, filtered %, attached_condition columns, using_join_buffer, using_filesort and using_temporary_table (EXPLAIN FORMAT=JSON has estimates only, no timings).", "tags": [ "devcloud" ], "x-mcp-tool": "query_plan_visualizer", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/QueryPlanVisualizerInput" }, "examples": { "example1": { "summary": "PostgreSQL EXPLAIN ANALYZE: seq scan, disk sort, batched hash", "value": { "text": " QUERY PLAN\n-------------------------------------------------------------------------------------------------------------------------------------------\n Sort (cost=152340.21..153372.39 rows=412873 width=72) (actual time=2211.041..2389.770 rows=412873 loops=1)\n Sort Key: o.created_at DESC\n Sort Method: external merge Disk: 48960kB\n Buffers: shared hit=1204 read=58210, temp read=12240 written=12268\n -> Hash Join (cost=31250.00..102149.11 rows=5000 width=72) (actual time=402.118..1712.904 rows=412873 loops=1)\n Hash Cond: (o.customer_id = c.id)\n -> Seq Scan on orders o (cost=0.00..68340.00 rows=5000 width=40) (actual time=0.031..1105.226 rows=412873 loops=1)\n Filter: ((status = 'shipped'::text) AND (created_at >= '2026-01-01 00:00:00'::timestamp without time zone))\n Rows Removed by Filter: 4587127\n -> Hash (cost=18750.00..18750.00 rows=1000000 width=36) (actual time=398.402..398.403 rows=1000000 loops=1)\n Buckets: 262144 Batches: 8 Memory Usage: 9201kB\n -> Seq Scan on customers c (cost=0.00..18750.00 rows=1000000 width=36) (actual time=0.012..141.882 rows=1000000 loops=1)\n Planning Time: 0.412 ms\n Execution Time: 2412.330 ms\n(14 rows)" } }, "example2": { "summary": "PostgreSQL JSON: nested loop with a misestimate", "value": { "text": "[{\"Plan\":{\"Node Type\":\"Aggregate\",\"Strategy\":\"Plain\",\"Partial Mode\":\"Simple\",\"Parallel Aware\":false,\"Startup Cost\":2412.3,\"Total Cost\":2412.31,\"Plan Rows\":1,\"Plan Width\":32,\"Actual Startup Time\":4380.2,\"Actual Total Time\":4380.21,\"Actual Rows\":1,\"Actual Loops\":1,\"Plans\":[{\"Node Type\":\"Nested Loop\",\"Parent Relationship\":\"Outer\",\"Parallel Aware\":false,\"Join Type\":\"Inner\",\"Startup Cost\":0.43,\"Total Cost\":2412.25,\"Plan Rows\":10,\"Plan Width\":10,\"Actual Startup Time\":0.09,\"Actual Total Time\":4362,\"Actual Rows\":20000,\"Actual Loops\":1,\"Inner Unique\":false,\"Plans\":[{\"Node Type\":\"Index Scan\",\"Parent Relationship\":\"Outer\",\"Parallel Aware\":false,\"Scan Direction\":\"Forward\",\"Index Name\":\"line_items_order_id_idx\",\"Relation Name\":\"line_items\",\"Alias\":\"li\",\"Startup Cost\":0.43,\"Total Cost\":12.5,\"Plan Rows\":10,\"Plan Width\":14,\"Actual Startup Time\":0.03,\"Actual Total Time\":35.1,\"Actual Rows\":20000,\"Actual Loops\":1,\"Index Cond\":\"(order_id = ANY ('{5001,5002,5003}'::integer[]))\",\"Rows Removed by Index Recheck\":0},{\"Node Type\":\"Seq Scan\",\"Parent Relationship\":\"Inner\",\"Parallel Aware\":false,\"Relation Name\":\"products\",\"Alias\":\"p\",\"Startup Cost\":0,\"Total Cost\":240,\"Plan Rows\":1,\"Plan Width\":14,\"Actual Startup Time\":0.1,\"Actual Total Time\":0.215,\"Actual Rows\":1,\"Actual Loops\":20000,\"Filter\":\"(sku = li.sku)\",\"Rows Removed by Filter\":1999}]}]},\"Planning Time\":0.3,\"Triggers\":[],\"Execution Time\":4381}]" } }, "example3": { "summary": "MySQL EXPLAIN FORMAT=JSON: full scan + filesort", "value": { "text": "{\"query_block\":{\"select_id\":1,\"cost_info\":{\"query_cost\":\"10431.25\"},\"ordering_operation\":{\"using_filesort\":true,\"nested_loop\":[{\"table\":{\"table_name\":\"o\",\"access_type\":\"ALL\",\"possible_keys\":null,\"rows_examined_per_scan\":98500,\"rows_produced_per_join\":985,\"filtered\":\"1.00\",\"cost_info\":{\"read_cost\":\"9947.75\",\"eval_cost\":\"98.50\",\"prefix_cost\":\"10046.25\",\"data_read_per_join\":\"30K\"},\"used_columns\":[\"id\",\"customer_id\",\"status\",\"created_at\"],\"attached_condition\":\"((`shop`.`o`.`status` = 'shipped') and (`shop`.`o`.`created_at` >= DATE'2026-01-01'))\"}},{\"table\":{\"table_name\":\"c\",\"access_type\":\"eq_ref\",\"possible_keys\":[\"PRIMARY\"],\"key\":\"PRIMARY\",\"used_key_parts\":[\"id\"],\"key_length\":\"4\",\"ref\":[\"shop.o.customer_id\"],\"rows_examined_per_scan\":1,\"rows_produced_per_join\":985,\"filtered\":\"100.00\",\"cost_info\":{\"read_cost\":\"246.25\",\"eval_cost\":\"98.50\",\"prefix_cost\":\"10391.00\",\"data_read_per_join\":\"61K\"},\"used_columns\":[\"id\",\"name\"]}}]}}}" } } } } } }, "responses": { "200": { "description": "Calculation result envelope.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/QueryPlanVisualizerResult" } } } }, "400": { "description": "Malformed JSON body.", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "422": { "description": "Invalid input (see errors[]).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "429": { "description": "Rate limit exceeded (see Retry-After).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } } } } }, "/api/v1/tool": { "get": { "operationId": "getToolDefinition", "summary": "Inputs, output schema and examples for this tool", "responses": { "200": { "description": "Tool definition.", "content": { "application/json": { "schema": { "type": "object" } } } } } } } }, "components": { "schemas": { "Problem": { "type": "object", "description": "RFC 9457 problem details. 422 responses include per-field `errors`.", "required": [ "type", "title", "status", "detail" ], "properties": { "type": { "type": "string" }, "title": { "type": "string" }, "status": { "type": "integer" }, "detail": { "type": "string" }, "code": { "type": "string" }, "errors": { "type": "array", "items": { "type": "object", "required": [ "field", "message" ], "properties": { "field": { "type": "string" }, "message": { "type": "string" } } } } } }, "QueryPlanVisualizerInput": { "type": "object", "additionalProperties": false, "properties": { "text": { "title": "EXPLAIN output", "description": "PostgreSQL: EXPLAIN (ANALYZE, BUFFERS) … as text, or EXPLAIN (ANALYZE, FORMAT JSON). MySQL: EXPLAIN FORMAT=JSON …. psql headers, \"+\" line continuations and \"(N rows)\" footers are ignored.", "type": "string", "maxLength": 3000000 }, "file": { "title": "Or upload the file", "description": "Read in memory as UTF-8 text and not stored. Max 5 MiB. Upload as {filename, contentType?, contentBase64}. Max 5120 KiB. Accepts .txt,.json,.sql,.log.", "type": "object", "additionalProperties": false, "required": [ "filename", "contentBase64" ], "properties": { "filename": { "type": "string" }, "contentType": { "type": "string" }, "contentBase64": { "type": "string" } } }, "misestimateFactor": { "title": "Flag row misestimates from", "description": "Ratio between estimated and actual rows per loop.", "type": "number", "minimum": 2, "maximum": 1000, "default": 10, "x-unit": "×" } }, "required": [] }, "QueryPlanVisualizerResult": { "type": "object", "additionalProperties": false, "required": [ "schemaVersion", "tool", "computedAt", "inputs", "summary", "result", "units", "assumptions", "sources", "warnings", "presentation", "links" ], "properties": { "schemaVersion": { "type": "string", "const": "1.0" }, "tool": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "version" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "version": { "type": "string" } } }, "computedAt": { "type": "string", "format": "date-time" }, "inputs": { "type": "object", "description": "Normalised inputs actually used, including applied defaults." }, "summary": { "type": "string" }, "result": { "type": "object", "additionalProperties": false, "required": [ "engine", "format", "analyzed", "planningMs", "executionMs", "totalCost", "nodeCount", "nodes", "findings", "indexCandidates" ], "properties": { "engine": { "type": "string", "enum": [ "postgresql", "mysql" ] }, "format": { "type": "string", "enum": [ "json", "text" ] }, "analyzed": { "type": "boolean" }, "planningMs": { "type": [ "number", "null" ] }, "executionMs": { "type": [ "number", "null" ] }, "totalCost": { "type": [ "number", "null" ] }, "nodeCount": { "type": "integer" }, "nodes": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "id", "parentId", "depth", "type", "label", "relation", "index", "startupCost", "totalCost", "exclusiveCost", "planRows", "actualRows", "loops", "inclusiveMs", "exclusiveMs", "rowsRatio", "details" ], "properties": { "id": { "type": "integer" }, "parentId": { "type": [ "integer", "null" ] }, "depth": { "type": "integer" }, "type": { "type": "string" }, "label": { "type": "string" }, "relation": { "type": [ "string", "null" ] }, "index": { "type": [ "string", "null" ] }, "startupCost": { "type": [ "number", "null" ] }, "totalCost": { "type": [ "number", "null" ] }, "exclusiveCost": { "type": [ "number", "null" ] }, "planRows": { "type": [ "number", "null" ] }, "actualRows": { "type": [ "number", "null" ] }, "loops": { "type": [ "number", "null" ] }, "inclusiveMs": { "type": [ "number", "null" ] }, "exclusiveMs": { "type": [ "number", "null" ] }, "rowsRatio": { "type": [ "number", "null" ] }, "details": { "type": "object", "additionalProperties": { "type": [ "string", "number", "boolean" ] } } } } }, "findings": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "nodeId", "severity", "issue", "detail", "suggestion" ], "properties": { "nodeId": { "type": "integer" }, "severity": { "type": "string", "enum": [ "high", "medium", "low" ] }, "issue": { "type": "string" }, "detail": { "type": "string" }, "suggestion": { "type": "string" } } } }, "indexCandidates": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "relation", "columns", "statement", "reason" ], "properties": { "relation": { "type": "string" }, "columns": { "type": "array", "items": { "type": "string" } }, "statement": { "type": "string" }, "reason": { "type": "string" } } } } } }, "units": { "type": "object", "additionalProperties": { "type": "string" } }, "assumptions": { "type": "array", "items": { "type": "string" } }, "sources": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "title" ], "properties": { "title": { "type": "string" }, "url": { "type": "string" }, "publisher": { "type": "string" }, "retrievedAt": { "type": "string" }, "note": { "type": "string" } } } }, "warnings": { "type": "array", "items": { "type": "string" } }, "presentation": { "type": "array", "items": { "type": "object" }, "description": "Display blocks used by the human page (same data)." }, "links": { "type": "object", "additionalProperties": false, "required": [ "human", "api", "openapi", "methodology" ], "properties": { "human": { "type": "string", "format": "uri" }, "api": { "type": "string", "format": "uri" }, "openapi": { "type": "string", "format": "uri" }, "methodology": { "type": "string", "format": "uri" } } } } } } } }