Overview
TiDB is an open-source distributed relational database management system. It is designed to process both OLTP (Online Transaction Processing) and OLAP (Online Analytical Processing) workloads.
TiDB supports representating query plans in text, table, JSON, and dot graph formats in its shell.
Example
CREATE TABLE t0 (c0 INT);
CREATE TABLE t1 (c0 INT);
CREATE TABLE t2 (c0 INT PRIMARY KEY);
INSERT INTO t0 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
INSERT INTO t2 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
Table format of the query plan
EXPLAIN SELECT t1.c0 FROM t0 JOIN t1 ON t0.c0 = t1.c0
WHERE t0.c0 < 100 GROUP BY t1.c0
UNION SELECT c0 FROM t2 WHERE c0 < 10;
The column id includes operations, and other columns include properties of associated operations.
| id | estRows | task | access object | operator info |
|---|---|---|---|---|
| HashAgg_16 | 6.82 | root | group by:Column#6, funcs:firstrow(Column#6)->Column#6 | |
| └─Union_17 | 7.49 | root | ||
| ├─HashAgg_19 | 4.15 | root | group by:test.t1.c0, funcs:firstrow(test.t1.c0)->test.t1.c0 | |
| │ └─HashJoin_21 | 4.15 | root | inner join, equal:[eq(test.t0.c0, test.t1.c0)] | |
| │ ├─TableReader_24(Build) | 3.32 | root | data:Selection_23 | |
| │ │ └─Selection_23 | 3.32 | cop[tikv] | lt(test.t0.c0, 100), not(isnull(test.t0.c0)) | |
| │ │ └─TableFullScan_22 | 10.00 | cop[tikv] | table:t0 | keep order:false, stats:pseudo |
| │ └─TableReader_27(Probe) | 3323.33 | root | data:Selection_26 | |
| │ └─Selection_26 | 3323.33 | cop[tikv] | lt(test.t1.c0, 100), not(isnull(test.t1.c0)) | |
| │ └─TableFullScan_25 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo |
| └─TableReader_30 | 4.17 | root | data:TableRangeScan_29 | |
| └─TableRangeScan_29 | 4.17 | cop[tikv] | table:t2 | range:[-inf,10), keep order:false, stats:pseudo |
JSON format of the query plan
EXPLAIN FORMAT=tidb_json SELECT t1.c0 FROM t0 JOIN t1 ON t0.c0 = t1.c0
WHERE t0.c0 < 100 GROUP BY t1.c0
UNION SELECT c0 FROM t2 WHERE c0 < 10;
Operations in the id fields, and properties are in other fields.
[
{
"id": "HashAgg_16",
"estRows": "6.82",
"taskType": "root",
"operatorInfo": "group by:Column#6, funcs:firstrow(Column#6)->Column#6",
"subOperators": [
{
"id": "Union_17",
"estRows": "7.49",
"taskType": "root",
"subOperators": [
{
"id": "HashAgg_19",
"estRows": "4.15",
"taskType": "root",
"operatorInfo": "group by:test.t1.c0, funcs:firstrow(test.t1.c0)->test.t1.c0",
"subOperators": [
{
"id": "HashJoin_21",
"estRows": "4.15",
"taskType": "root",
"operatorInfo": "inner join, equal:[eq(test.t0.c0, test.t1.c0)]",
"subOperators": [
{
"id": "TableReader_24(Build)",
"estRows": "3.32",
"taskType": "root",
"operatorInfo": "data:Selection_23",
"subOperators": [
{
"id": "Selection_23",
"estRows": "3.32",
"taskType": "cop[tikv]",
"operatorInfo": "lt(test.t0.c0, 100), not(isnull(test.t0.c0))",
"subOperators": [
{
"id": "TableFullScan_22",
"estRows": "10.00",
"taskType": "cop[tikv]",
"accessObject": "table:t0",
"operatorInfo": "keep order:false, stats:pseudo"
}
]
}
]
},
{
"id": "TableReader_27(Probe)",
"estRows": "3323.33",
"taskType": "root",
"operatorInfo": "data:Selection_26",
"subOperators": [
{
"id": "Selection_26",
"estRows": "3323.33",
"taskType": "cop[tikv]",
"operatorInfo": "lt(test.t1.c0, 100), not(isnull(test.t1.c0))",
"subOperators": [
{
"id": "TableFullScan_25",
"estRows": "10000.00",
"taskType": "cop[tikv]",
"accessObject": "table:t1",
"operatorInfo": "keep order:false, stats:pseudo"
}
]
}
]
}
]
}
]
},
{
"id": "TableReader_30",
"estRows": "4.17",
"taskType": "root",
"operatorInfo": "data:TableRangeScan_29",
"subOperators": [
{
"id": "TableRangeScan_29",
"estRows": "4.17",
"taskType": "cop[tikv]",
"accessObject": "table:t2",
"operatorInfo": "range:[-inf,10), keep order:false, stats:pseudo"
}
]
}
]
}
]
}
]