{
  "$schema": "https://myflames.dev/schemas/sidecar-v1.json",
  "schema_version": "1.3",
  "generated_at": "2026-04-25T12:51:24Z",
  "myflames_version": "1.5.0",
  "source": {
    "type": "file",
    "engine": "mysql",
    "fixture_path": "/Users/viniciusgrippa/Downloads/git/myflames/test/mysql-explain-hash-join.json"
  },
  "plan_summary": {
    "total_time_ms": 8.25,
    "rows_sent": 12000,
    "rows_examined_estimate": 15000,
    "operator_count": 3,
    "max_depth": 2
  },
  "optimizer_switches": [
    {
      "name": "hash_join",
      "value": "on",
      "explanation": "Builds an in-memory hash table on the smaller (build) input and probes it from the other side. Uses join_buffer_size; spills to a tmp file (and tmpdir) if the build side does not fit.",
      "node_labels": [
        "Inner hash join (orders.user_id = users.id)"
      ]
    }
  ],
  "warnings": [
    {
      "severity": "warn",
      "category": "full_scan",
      "text": "Full table scan: users (3000 rows), orders (12000 rows)",
      "source": "plan",
      "node_labels": [
        "Table scan [users]",
        "Table scan [orders]"
      ]
    },
    {
      "severity": "warn",
      "category": "hash_join",
      "text": "1 hash join(s) — uses join_buffer_size (~12000 rows in build phase)",
      "source": "plan",
      "node_labels": [
        "Inner hash join (orders.user_id = users.id)"
      ]
    }
  ],
  "suggestions": [
    {
      "severity": "high",
      "category": "index",
      "action": "Add indexes on filter/join columns to avoid full table scans",
      "source": "plan"
    },
    {
      "severity": "medium",
      "category": "tuning_variable",
      "action": "Increase join_buffer_size if hash joins are slow or spill to disk",
      "source": "plan",
      "target_variable": "join_buffer_size"
    }
  ],
  "executive_summary": "Query scans 2 tables and hash-joins 1 pair; returns 12,000 rows in 8.2 ms. Main finding: hash join uses join_buffer_size; an index on the join column would be faster.",
  "plan_tree": {
    "node_id": "n:d017511b6657",
    "short_label": "Inner hash join (orders.user_id = users.id)",
    "folded_label": "Inner hash join (orders.user_id = users.id) starts=1 rows=12000",
    "children": [
      {
        "node_id": "n:f78dc713f35d",
        "short_label": "Table scan [users]",
        "folded_label": "TABLE SCAN [users] starts=1 rows=3000",
        "children": []
      },
      {
        "node_id": "n:ec47220d7a5f",
        "short_label": "Table scan [orders]",
        "folded_label": "TABLE SCAN [orders] starts=1 rows=12000",
        "children": []
      }
    ]
  },
  "query": {
    "raw": "/* select#1 */ select `u`.`name` AS `name`, `o`.`total` AS `total` from `testdb`.`users` `u` join `testdb`.`orders` `o` on (`o`.`user_id` = `u`.`id`)",
    "beautified": "select u.name AS name, o.total AS total\nfrom testdb.users u\n  join testdb.orders o on (o.user_id = u.id)"
  },
  "primary_action": {
    "ref": "suggestions[0]"
  },
  "teach_hooks": [
    {
      "lesson": "hash",
      "match": {
        "folded_label": "Inner hash join (orders.user_id = users.id) starts=1 rows=12000",
        "short_label": "Inner hash join (orders.user_id = users.id)"
      },
      "controls": {
        "build_rows": 3000,
        "probe_rows": 12000,
        "row_size": 200
      },
      "note": "Inner hash join (orders.user_id = users.id)",
      "query_sql": "/* select#1 */ select `u`.`name` AS `name`, `o`.`total` AS `total` from `testdb`.`users` `u` join `testdb`.`orders` `o` on (`o`.`user_id` = `u`.`id`)"
    },
    {
      "lesson": "full_scan",
      "match": {
        "folded_label": "TABLE SCAN [users] starts=1 rows=3000",
        "short_label": "Table scan [users]"
      },
      "controls": {
        "rows": 3000,
        "row_size": 200,
        "selectivity": 100.0
      },
      "note": "Table scan on users (users)",
      "query_sql": "/* select#1 */ select `u`.`name` AS `name`, `o`.`total` AS `total` from `testdb`.`users` `u` join `testdb`.`orders` `o` on (`o`.`user_id` = `u`.`id`)"
    },
    {
      "lesson": "full_scan",
      "match": {
        "folded_label": "TABLE SCAN [orders] starts=1 rows=12000",
        "short_label": "Table scan [orders]"
      },
      "controls": {
        "rows": 12000,
        "row_size": 200,
        "selectivity": 100.0
      },
      "note": "Table scan on orders (hash build) (orders)",
      "query_sql": "/* select#1 */ select `u`.`name` AS `name`, `o`.`total` AS `total` from `testdb`.`users` `u` join `testdb`.`orders` `o` on (`o`.`user_id` = `u`.`id`)"
    }
  ],
  "operator_complexities": [
    {
      "node_id": "n:d017511b6657",
      "folded_label": "Inner hash join (orders.user_id = users.id) starts=1 rows=12000",
      "short_label": "Inner hash join (orders.user_id = users.id)",
      "complexity": {
        "big_o": "O(n + m)",
        "short": "n + m",
        "severity": "good",
        "rationale": "Hash join: builds a hash on one side (O(m)), streams the other past it (O(n)). Disk-spill does NOT change the asymptotic class — only the constants.",
        "confidence": "exact",
        "learn_more": "hash_join"
      }
    },
    {
      "node_id": "n:f78dc713f35d",
      "folded_label": "TABLE SCAN [users] starts=1 rows=3000",
      "short_label": "Table scan [users]",
      "complexity": {
        "big_o": "O(n)",
        "short": "n",
        "severity": "medium",
        "rationale": "Full table scan: the storage engine returns every row; cost scales with the table size.",
        "confidence": "exact",
        "learn_more": "full_table_scan"
      }
    },
    {
      "node_id": "n:ec47220d7a5f",
      "folded_label": "TABLE SCAN [orders] starts=1 rows=12000",
      "short_label": "Table scan [orders]",
      "complexity": {
        "big_o": "O(n)",
        "short": "n",
        "severity": "medium",
        "rationale": "Full table scan: the storage engine returns every row; cost scales with the table size.",
        "confidence": "exact",
        "learn_more": "full_table_scan"
      }
    }
  ]
}