mariadb/mysql-test/r/explain_json.result

drop table if exists t0,t1;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
explain format=json select * from t0;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100
    }
  }
}
explain format=json select * from t0 where 1>2;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE"
    }
  }
}
explain format=json select * from t0 where a<3;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "(t0.a < 3)"
    }
  }
}
# Try a basic join
create table t1 (a int, b int, filler char(32), key(a));
insert into t1 
select 
a.a + b.a* 10 + c.a * 100, 
a.a + b.a* 10 + c.a * 100,
'filler'
from t0 a, t0 b, t0 c;
explain format=json select * from t0,t1 where t1.a=t0.a;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "(t0.a is not null)"
    },
    "table": {
      "table_name": "t1",
      "access_type": "ref",
      "possible_keys": ["a"],
      "key": "a",
      "key_length": "5",
      "used_key_parts": ["a"],
      "ref": ["test.t0.a"],
      "rows": 1,
      "filtered": 100
    }
  }
}
# Try range and index_merge
create table t2 (a1 int, a2 int, b1 int, b2 int, key(a1,a2), key(b1,b2));
insert into t2 select a,a,a,a from t1;
explain format=json select * from t2 where a1<5;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t2",
      "access_type": "range",
      "possible_keys": ["a1"],
      "key": "a1",
      "key_length": "5",
      "used_key_parts": ["a1"],
      "rows": 5,
      "filtered": 100,
      "index_condition": "(t2.a1 < 5)"
    }
  }
}
explain format=json select * from t2 where a1=1 or b1=2;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t2",
      "access_type": "index_merge",
      "possible_keys": ["a1", "b1"],
      "key_length": "5,5",
      "index_merge": {
        "sort_union": {
          "range": {
            "key": "a1",
            "used_key_parts": ["a1"]
          },
          "range": {
            "key": "b1",
            "used_key_parts": ["b1"]
          }
        }
      },
      "rows": 2,
      "filtered": 100,
      "attached_condition": "((t2.a1 = 1) or (t2.b1 = 2))"
    }
  }
}
explain format=json select * from t2 where a1=1 or (b1=2 and b2=3);
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t2",
      "access_type": "index_merge",
      "possible_keys": ["a1", "b1"],
      "key_length": "5,10",
      "index_merge": {
        "sort_union": {
          "range": {
            "key": "a1",
            "used_key_parts": ["a1"]
          },
          "range": {
            "key": "b1",
            "used_key_parts": ["b1", "b2"]
          }
        }
      },
      "rows": 2,
      "filtered": 100,
      "attached_condition": "((t2.a1 = 1) or ((t2.b1 = 2) and (t2.b2 = 3)))"
    }
  }
}
# Try ref access on two key components
explain format=json select * from t0,t2 where t2.b1=t0.a and t2.b2=4;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "(t0.a is not null)"
    },
    "table": {
      "table_name": "t2",
      "access_type": "ref",
      "possible_keys": ["b1"],
      "key": "b1",
      "key_length": "10",
      "used_key_parts": ["b1", "b2"],
      "ref": ["test.t0.a", "const"],
      "rows": 1,
      "filtered": 100
    }
  }
}
drop table t1,t2;
#
# Try a UNION
#
explain format=json select * from t0 A union     select * from t0 B;
EXPLAIN
{
  "query_block": {
    "union_result": {
      "table_name": "<union1,2>",
      "access_type": "ALL",
      "query_specifications": [
        {
          "query_block": {
            "select_id": 1,
            "table": {
              "table_name": "A",
              "access_type": "ALL",
              "rows": 10,
              "filtered": 100
            }
          }
        },
        {
          "query_block": {
            "select_id": 2,
            "table": {
              "table_name": "B",
              "access_type": "ALL",
              "rows": 10,
              "filtered": 100
            }
          }
        }
      ]
    }
  }
}
explain format=json select * from t0 A union all select * from t0 B;
EXPLAIN
{
  "query_block": {
    "union_result": {
      "table_name": "<union1,2>",
      "access_type": "ALL",
      "query_specifications": [
        {
          "query_block": {
            "select_id": 1,
            "table": {
              "table_name": "A",
              "access_type": "ALL",
              "rows": 10,
              "filtered": 100
            }
          }
        },
        {
          "query_block": {
            "select_id": 2,
            "table": {
              "table_name": "B",
              "access_type": "ALL",
              "rows": 10,
              "filtered": 100
            }
          }
        }
      ]
    }
  }
}
#
# Subqueries
#
create table t1 (a int, b int);
insert into t1 select a,a from t0;
explain format=json select a, a > (select max(b) from t1 where t1.b=t0.a) from t0;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100
    },
    "subqueries": [
      {
        "query_block": {
          "select_id": 2,
          "table": {
            "table_name": "t1",
            "access_type": "ALL",
            "rows": 10,
            "filtered": 100,
            "attached_condition": "(t1.b = t0.a)"
          }
        }
      }
    ]
  }
}
explain format=json 
select * from t0 where 
a > (select max(b) from t1 where t1.b=t0.a) or a < 3 ;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "((t0.a > (subquery#2)) or (t0.a < 3))"
    },
    "subqueries": [
      {
        "query_block": {
          "select_id": 2,
          "table": {
            "table_name": "t1",
            "access_type": "ALL",
            "rows": 10,
            "filtered": 100,
            "attached_condition": "(t1.b = t0.a)"
          }
        }
      }
    ]
  }
}
drop table t1;
#
# Join buffering
#
create table t1 (a int, b int);
insert into t1 select tbl1.a+10*tbl2.a, tbl1.a+10*tbl2.a from t0 tbl1, t0 tbl2;
explain format=json
select * from t1 tbl1, t1 tbl2 where tbl1.a=tbl2.a and tbl1.b < 3 and tbl2.b < 5;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "tbl1",
      "access_type": "ALL",
      "rows": 100,
      "filtered": 100,
      "attached_condition": "(tbl1.b < 3)"
    },
    "block-nl-join": {
      "table": {
        "table_name": "tbl2",
        "access_type": "ALL",
        "rows": 100,
        "filtered": 100,
        "attached_condition": "(tbl2.b < 5)"
      },
      "buffer_type": "flat",
      "join_type": "BNL",
      "attached_condition": "(tbl2.a = tbl1.a)"
    }
  }
}
drop table t1;
#
# Single-table UPDATE/DELETE
#
explain format=json delete from t0;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Deleting all rows"
    }
  }
}
explain format=json delete from t0 where 1 > 2;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE"
    }
  }
}
explain format=json delete from t0 where a < 3;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "delete": 1,
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "attached_condition": "(t0.a < 3)"
    }
  }
}
explain format=json update t0 set a=3 where a in (2,3,4);
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "update": 1,
      "table_name": "t0",
      "access_type": "ALL",
      "rows": 10,
      "attached_condition": "(t0.a in (2,3,4))"
    }
  }
}
#
# A derived table
#
create table t1 (a int, b int);
insert into t1 select a,a from t0;
explain format=json
select * from (select a, count(*) as cnt from t1 group by a) as tbl
where cnt>0;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "<derived2>",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "(tbl.cnt > 0)",
      "materialized": {
        "query_block": {
          "select_id": 2,
          "table": {
            "table_name": "t1",
            "access_type": "ALL",
            "rows": 10,
            "filtered": 100
          }
        }
      }
    }
  }
}
explain format=json
select * from (select a, count(*) as cnt from t1 group by a) as tbl1, t1 as
tbl2 where cnt=tbl2.a;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "tbl2",
      "access_type": "ALL",
      "rows": 10,
      "filtered": 100,
      "attached_condition": "(tbl2.a is not null)"
    },
    "table": {
      "table_name": "<derived2>",
      "access_type": "ref",
      "possible_keys": ["key0"],
      "key": "key0",
      "key_length": "8",
      "used_key_parts": ["cnt"],
      "ref": ["test.tbl2.a"],
      "rows": 2,
      "filtered": 100,
      "attached_condition": "(tbl1.cnt = tbl2.a)",
      "materialized": {
        "query_block": {
          "select_id": 2,
          "table": {
            "table_name": "t1",
            "access_type": "ALL",
            "rows": 10,
            "filtered": 100
          }
        }
      }
    }
  }
}
drop table t0;