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EXPLAIN FORMAT=JSON: Full scan on NULL key (join case)

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This commit is contained in:
Sergei Petrunia
2014-12-06 03:11:03 +03:00
parent a80a797686
commit 5ee1c25fa8
5 changed files with 85 additions and 0 deletions
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59
mysql-test/r/explain_json.result
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@ -719,3 +719,62 @@ EXPLAIN
}
drop table t1;
drop table t0;
#
# MDEV-7265: "Full scan on NULL key", the join case
#
CREATE TABLE t1 (a INT, KEY(a));
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (3),(4);
EXPLAIN FORMAT=JSON SELECT * FROM t1 AS outer_t1 WHERE a <> ALL ( SELECT a FROM t1, t2 WHERE b <> outer_t1.a );
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "outer_t1",
"access_type": "index",
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"rows": 2,
"filtered": 100,
"attached_condition": "(not(<in_optimizer>(outer_t1.a,<exists>(subquery#2))))",
"using_index": true
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"full-scan-on-null_key": {
"table": {
"table_name": "t1",
"access_type": "ref_or_null",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"ref": ["func"],
"rows": 2,
"filtered": 100,
"attached_condition": "trigcond(((<cache>(outer_t1.a) = t1.a) or isnull(t1.a)))",
"using_index": true
}
},
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "((t2.b <> outer_t1.a) and trigcond(((<cache>(outer_t1.a) = t1.a) or isnull(t1.a))))"
}
}
}
]
}
}
DROP TABLE t1,t2;

14
mysql-test/t/explain_json.test
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@ -153,3 +153,17 @@ select * from t1 tbl1, t1 tbl2 where tbl2.a < tbl1.b;
drop table t1;
drop table t0;
--echo #
--echo # MDEV-7265: "Full scan on NULL key", the join case
--echo #
CREATE TABLE t1 (a INT, KEY(a));
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (3),(4);
EXPLAIN FORMAT=JSON SELECT * FROM t1 AS outer_t1 WHERE a <> ALL ( SELECT a FROM t1, t2 WHERE b <> outer_t1.a );
DROP TABLE t1,t2;

8
sql/sql_explain.cc
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@ -1139,6 +1139,8 @@ void Explain_table_access::tag_to_json(Json_writer *writer, enum explain_extra_t
case ET_START_TEMPORARY:
case ET_END_TEMPORARY:
/* Handled as "duplicates_removal: { ... } */
case ET_FULL_SCAN_ON_NULL_KEY:
/* Handled in full_scan_on_null_key */
break;
case ET_FIRST_MATCH:
writer->add_member("first_match").add_str(firstmatch_table_name.c_ptr());
@ -1188,6 +1190,9 @@ void Explain_table_access::print_explain_json(Explain_query *query,
add_json_keyset(writer, "keys", &possible_keys);
}
if (full_scan_on_null_key)
writer->add_member("full-scan-on-null_key").start_object();
writer->add_member("table").start_object();
writer->add_member("table_name").add_str(table_name);
@ -1289,6 +1294,9 @@ void Explain_table_access::print_explain_json(Explain_query *query,
tag_to_json(writer, extra_tags.at(i));
}
if (full_scan_on_null_key)
writer->end_object(); //"full-scan-on-null_key"
if (range_checked_fer)
writer->end_object(); // "range-checked-for-each-record"

3
sql/sql_explain.h
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@ -562,6 +562,7 @@ public:
non_merged_sjm_number(0),
extra_tags(root),
range_checked_fer(NULL),
full_scan_on_null_key(false),
start_dups_weedout(false),
end_dups_weedout(false),
where_cond(NULL),
@ -635,6 +636,8 @@ public:
/* Non-NULL values means this tab uses "range checked for each record" */
Explain_range_checked_fer *range_checked_fer;
bool full_scan_on_null_key;
// valid with ET_USING_JOIN_BUFFER
EXPLAIN_BKA_TYPE bka_type;

1
sql/sql_select.cc
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@ -23687,6 +23687,7 @@ void JOIN_TAB::save_explain_data(Explain_table_access *eta, table_map prefix_tab
if (tab->ref.cond_guards[part])
{
eta->push_extra(ET_FULL_SCAN_ON_NULL_KEY);
eta->full_scan_on_null_key= true;
break;
}
}