{
  "$schema": "https://myflames.dev/schemas/sidecar-v1.json",
  "schema_version": "1.3",
  "generated_at": "2026-04-25T12:51:22Z",
  "myflames_version": "1.5.0",
  "source": {
    "type": "file",
    "engine": "mariadb",
    "fixture_path": "/Users/viniciusgrippa/Downloads/git/myflames/test/mariadb-explain-weedout.json"
  },
  "plan_summary": {
    "total_time_ms": 0.0,
    "rows_sent": 1,
    "rows_examined_estimate": 1001,
    "operator_count": 4,
    "max_depth": 3
  },
  "optimizer_switches": [
    {
      "name": "semijoin",
      "value": "on",
      "explanation": "IN / EXISTS subqueries are rewritten into a semi-join with the outer query and then resolved via one of the semijoin strategies (firstmatch, loosescan, duplicateweedout, or materialization).",
      "node_labels": [
        "Remove duplicates using temporary table (weedout)"
      ]
    },
    {
      "name": "duplicateweedout",
      "value": "on",
      "explanation": "Semijoin strategy: runs the subquery as a normal inner join and then removes duplicate outer rows using a temporary table keyed on their row IDs.",
      "node_labels": [
        "Remove duplicates using temporary table (weedout)"
      ]
    }
  ],
  "warnings": [
    {
      "severity": "warn",
      "category": "full_scan",
      "text": "Full table scan: t2 (1000 rows)",
      "source": "plan",
      "node_labels": [
        "Table scan [t2]"
      ]
    }
  ],
  "suggestions": [
    {
      "severity": "high",
      "category": "index",
      "action": "Add indexes on filter/join columns to avoid full table scans",
      "source": "plan"
    }
  ],
  "executive_summary": "Query scans 1 table; examines ~1,001 rows to return 1. Main finding: no index covers (y, x) on t2.",
  "plan_tree": {
    "node_id": "n:974fce611738",
    "short_label": "Remove duplicates using temporary table (weedout)",
    "folded_label": "Remove duplicates using temporary table (weedout) starts=1 rows=1",
    "children": [
      {
        "node_id": "n:c2114456d668",
        "short_label": "Nested loop inner join",
        "folded_label": "NESTED LOOP INNER starts=1 rows=1",
        "children": [
          {
            "node_id": "n:64a037ea2b77",
            "short_label": "Table scan [t2]",
            "folded_label": "TABLE SCAN [t2] starts=1 rows=1000",
            "children": []
          },
          {
            "node_id": "n:8b0bb271f704",
            "short_label": "Index lookup [t1.PRIMARY]",
            "folded_label": "INDEX LOOKUP [t1.PRIMARY] starts=49 rows=1",
            "children": []
          }
        ]
      }
    ]
  },
  "index_suggestions": [
    {
      "table": "t2",
      "columns": [
        "y",
        "x"
      ],
      "ddl": "CREATE INDEX idx_t2_y_x ON t2 (y, x);",
      "reason": "Full scan on t2 with filter on (y, x)"
    }
  ],
  "primary_action": {
    "ref": "suggestions[0]"
  },
  "teach_hooks": [
    {
      "lesson": "semijoin_weedout",
      "match": {
        "folded_label": "Remove duplicates using temporary table (weedout) starts=1 rows=1",
        "short_label": "Remove duplicates using temporary table (weedout)"
      },
      "controls": {
        "outer_rows": 1,
        "inner_matches": 5,
        "row_size": 200
      },
      "note": "Remove duplicates using temporary table (weedout)"
    },
    {
      "lesson": "nested_loop",
      "match": {
        "folded_label": "NESTED LOOP INNER starts=1 rows=1",
        "short_label": "Nested loop inner join"
      },
      "controls": {
        "outer_rows": 1000,
        "inner_rows": 49,
        "row_size": 200
      },
      "note": "Nested loop inner join"
    },
    {
      "lesson": "full_scan",
      "match": {
        "folded_label": "TABLE SCAN [t2] starts=1 rows=1000",
        "short_label": "Table scan [t2]"
      },
      "controls": {
        "rows": 1000,
        "row_size": 200,
        "selectivity": 10.0
      },
      "note": "Table scan on t2 (t2)"
    },
    {
      "lesson": "non_unique_lookup",
      "match": {
        "folded_label": "INDEX LOOKUP [t1.PRIMARY] starts=49 rows=1",
        "short_label": "Index lookup [t1.PRIMARY]"
      },
      "controls": {
        "rows": 49,
        "selectivity": 40.0,
        "covering": false
      },
      "note": "Index lookup on t1 using PRIMARY (t1)"
    }
  ],
  "operator_complexities": [
    {
      "node_id": "n:974fce611738",
      "folded_label": "Remove duplicates using temporary table (weedout) starts=1 rows=1",
      "short_label": "Remove duplicates using temporary table (weedout)",
      "complexity": {
        "big_o": "O(n log n)",
        "short": "n log n",
        "severity": "medium",
        "rationale": "DuplicateWeedout semijoin: runs as a plain inner join, then drops duplicates using a temp-table index on the outer row IDs.",
        "confidence": "typical",
        "learn_more": "duplicate_weedout"
      }
    },
    {
      "node_id": "n:c2114456d668",
      "folded_label": "NESTED LOOP INNER starts=1 rows=1",
      "short_label": "Nested loop inner join",
      "complexity": {
        "big_o": "O(n · log m)",
        "short": "n · log m",
        "severity": "medium",
        "rationale": "Indexed nested loop: each outer row probes the inner table via an index descent.",
        "confidence": "exact",
        "learn_more": "nested_loop_join"
      }
    },
    {
      "node_id": "n:64a037ea2b77",
      "folded_label": "TABLE SCAN [t2] starts=1 rows=1000",
      "short_label": "Table scan [t2]",
      "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:8b0bb271f704",
      "folded_label": "INDEX LOOKUP [t1.PRIMARY] starts=49 rows=1",
      "short_label": "Index lookup [t1.PRIMARY]",
      "complexity": {
        "big_o": "O(log n + k)",
        "short": "log n + k",
        "severity": "good",
        "rationale": "Index lookup (ref): one B+tree descent then a sequential walk over k matching index entries. k = matching rows for the indexed predicate.",
        "confidence": "exact",
        "learn_more": "index_lookup"
      }
    }
  ]
}