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查看执行计划
更新时间：2026-06-13 13:49:40
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执行计划是对一条 SQL 查询语句在数据库中执行过程的描述，通常用于分析某条 SQL 的性能问题，读懂执行计划是 SQL 优化的先决条件。用户可以通过 EXPLAIN 命令查看优化器针对指定 SQL 生成的逻辑执行计划。
有关 SQL 执行计划的详细信息，请参见 SQL 执行计划。
有关分布式执行计划的详细信息，请参见 分布式执行计划管理。
EXPLAIN 命令格式
OceanBase 数据库的执行计划命令有三种模式：EXPLAIN BASIC、EXPLAIN 和 EXPLAIN EXTENDED。这三种模式对执行计划展现不同粒度的细节信息:
EXPLAIN BASIC命令用于最基本的计划展示。EXPLAIN EXTENDED命令用于最详细的计划展示（通常在排查问题时使用这种展示模式）。EXPLAIN命令所展示的信息可以帮助普通用户了解整个计划的执行方式。
语法如下：
EXPLAIN [explain_type] dml_statement;
explain_type：
BASIC [pretty_name]
| OUTLINE [pretty_name]
| EXTENDED [pretty_name]
| EXTENDED_NOADDR [pretty_name]
| PARTITIONS [pretty_name]
| FORMAT = { TRADITIONAL | JSON }
pretty_name:
PRETTY
| PRETTY_COLOR
dml_statement:
SELECT statement
| DELETE statement
| INSERT statement
| REPLACE statement
| UPDATE statement
EXPLAIN命令适用于SELECT、DELETE、INSERT、REPLACE和UPDATE语句，显示优化器所提供的有关语句执行计划的信息，包括如何处理该语句，如何联接表以及以何种顺序联接表等信息。一般来说，可以使用
EXPLAIN EXTENDED命令，将表扫描的范围段展示出来。使用EXPLAIN OUTLINE命令可以显示 Outline 信息。FORMAT选项可用于选择输出格式。TRADITIONAL表示以表格格式显示输出，这也是默认设置。JSON表示以JSON格式显示信息。使用
EXPLAIN PARTITITIONS也可用于检查涉及分区表的查询。如果检查针对非分区表的查询，则不会产生错误，但PARTIONS列的值始终为NULL。对于复杂的执行计划，可以使用
PRETTY或者PRETTY_COLOR选项将计划树中的父节点和子节点使用树线或彩色树线连接起来，使得执行计划展示更方便阅读。
使用黑屏环境查看执行计划示例
使用
EXPLAIN BASIC命令展示执行计划。obclient> CREATE TABLE t1(a INT PRIMARY KEY, b INT, c INT, KEY k1(b)); Query OK, 0 rows affected obclient> CREATE TABLE t2(a INT PRIMARY KEY, b INT, c INT, KEY k1(b)); Query OK, 0 rows affected obclient> EXPLAIN BASIC SELECT * FROM t1,t2 WHERE t1.a = t2.a\G *************************** 1. row *************************** Query Plan: ===================== |ID|OPERATOR |NAME| --------------------- |0 |MERGE JOIN | | |1 | TABLE SCAN|t1 | |2 | TABLE SCAN|t2 | ===================== Outputs & filters: ------------------------------------- 0 - output([t1.a], [t1.b], [t1.c], [t2.a], [t2.b], [t2.c]), filter(nil), equal_conds([t1.a = t2.a]), other_conds(nil) 1 - output([t1.a], [t1.b], [t1.c]), filter(nil), access([t1.a], [t1.b], [t1.c]), partitions(p0) 2 - output([t2.a], [t2.b], [t2.c]), filter(nil), access([t2.a], [t2.b], [t2.c]), partitions(p0)使用
EXPLAIN命令展示执行计划。obclient> EXPLAIN SELECT * FROM t1,t2 WHERE t1.a = t2.a\G *************************** 1. row *************************** Query Plan: ====================================== |ID|OPERATOR |NAME|EST. ROWS|COST | -------------------------------------- |0 |MERGE JOIN | |100001 |119783| |1 | TABLE SCAN|t1 |100000 |38681 | |2 | TABLE SCAN|t2 |100000 |38681 | ====================================== Outputs & filters: ------------------------------------- 0 - output([t1.a], [t1.b], [t1.c], [t2.a], [t2.b], [t2.c]), filter(nil), equal_conds([t1.a = t2.a]), other_conds(nil) 1 - output([t1.a], [t1.b], [t1.c]), filter(nil), access([t1.a], [t1.b], [t1.c]), partitions(p0) 2 - output([t2.a], [t2.b], [t2.c]), filter(nil), access([t2.a], [t2.b], [t2.c]), partitions(p0)使用
EXPLAIN EXTENDED命令展示执行计划。obclient> EXPLAIN EXTENDED SELECT * FROM t1,t2 WHERE t1.a = t2.a\G *************************** 1. row *************************** Query Plan: ====================================== |ID|OPERATOR |NAME|EST. ROWS|COST | -------------------------------------- |0 |MERGE JOIN | |100001 |119783| |1 | TABLE SCAN|t1 |100000 |38681 | |2 | TABLE SCAN|t2 |100000 |38681 | ====================================== Outputs & filters: ------------------------------------- 0 - output([t1.a(0x7f1c68e79310)], [t1.b(0x7f1c68e79950)], [t1.c(0x7f1c68e79c10)], [t2.a(0x7f1c68e795d0)], [t2.b(0x7f1c68e79ed0)], [t2.c(0x7f1c68e7a190)]), filter(nil), equal_conds([t1.a(0x7f1c68e79310) = t2.a(0x7f1c68e795d0)(0x7f1c68e78c20)]), other_conds(nil), merge_directions([ASC]) 1 - output([t1.a(0x7f1c68e79310)], [t1.b(0x7f1c68e79950)], [t1.c(0x7f1c68e79c10)]), filter(nil), access([t1.a(0x7f1c68e79310)], [t1.b(0x7f1c68e79950)], [t1.c(0x7f1c68e79c10)]), partitions(p0), is_index_back=false, range_key([t1.a(0x7f1c68e79310)]), range(MIN ; MAX)always true 2 - output([t2.a(0x7f1c68e795d0)], [t2.b(0x7f1c68e79ed0)], [t2.c(0x7f1c68e7a190)]), filter(nil), access([t2.a(0x7f1c68e795d0)], [t2.b(0x7f1c68e79ed0)], [t2.c(0x7f1c68e7a190)]), partitions(p0), is_index_back=false, range_key([t2.a(0x7f1c68e795d0)]), range(MIN ; MAX)always true Used Hint: ------------------------------------- /*+ */ Outline Data: ------------------------------------- /*+ BEGIN_OUTLINE_DATA LEADING(@"SEL$1" ("test.t1"@"SEL$1" "test.t2"@"SEL$1" )) USE_MERGE(@"SEL$1" ("test.t2"@"SEL$1" )) PQ_DISTRIBUTE(@"SEL$1" ("test.t2"@"SEL$1" ) LOCAL LOCAL) FULL(@"SEL$1" "test.t1"@"SEL$1") FULL(@"SEL$1" "test.t2"@"SEL$1") END_OUTLINE_DATA */ Plan Type: ------------------------------------- LOCAL Optimization Info: ------------------------------------- t1:table_rows:100000, physical_range_rows:100000, logical_range_rows:100000, index_back_rows:0, output_rows:100000, est_method:default_stat, optimization_method=cost_based, avaiable_index_name[t1], pruned_index_name[k1] t2:table_rows:100000, physical_range_rows:100000, logical_range_rows:100000, index_back_rows:0, output_rows:100000, est_method:default_stat, optimization_method=cost_based, avaiable_index_name[t2], pruned_index_name[k1] Parameters -------------------------------------使用
EXPLAIN EXTENDED_NOADDR命令展示执行计划。obclient> EXPLAIN EXTENDED_NOADDR SELECT * FROM t1,t2 WHERE t1.a = t2.a\G *************************** 1. row *************************** Query Plan: ====================================== |ID|OPERATOR |NAME|EST. ROWS|COST | -------------------------------------- |0 |MERGE JOIN | |100001 |119783| |1 | TABLE SCAN|t1 |100000 |38681 | |2 | TABLE SCAN|t2 |100000 |38681 | ====================================== Outputs & filters: ------------------------------------- 0 - output([t1.a], [t1.b], [t1.c], [t2.a], [t2.b], [t2.c]), filter(nil), equal_conds([t1.a = t2.a]), other_conds(nil) 1 - output([t1.a], [t1.b], [t1.c]), filter(nil), access([t1.a], [t1.b], [t1.c]), partitions(p0), is_index_back=false, range_key([t1.a]), range(MIN ; MAX)always true 2 - output([t2.a], [t2.b], [t2.c]), filter(nil), access([t2.a], [t2.b], [t2.c]), partitions(p0), is_index_back=false, range_key([t2.a]), range(MIN ; MAX)always true使用
EXPLAIN OUTLINE命令可以显示 Outline 信息。obclient> EXPLAIN OUTLINE SELECT * FROM t1,t2 WHERE t1.a = t2.a\G *************************** 1. row *************************** Query Plan: ====================================== |ID|OPERATOR |NAME|EST. ROWS|COST | -------------------------------------- |0 |MERGE JOIN | |100001 |119783| |1 | TABLE SCAN|t1 |100000 |38681 | |2 | TABLE SCAN|t2 |100000 |38681 | ====================================== Outputs & filters: ------------------------------------- 0 - output([t1.a], [t1.b], [t1.c], [t2.a], [t2.b], [t2.c]), filter(nil), equal_conds([t1.a = t2.a]), other_conds(nil) 1 - output([t1.a], [t1.b], [t1.c]), filter(nil), access([t1.a], [t1.b], [t1.c]), partitions(p0) 2 - output([t2.a], [t2.b], [t2.c]), filter(nil), access([t2.a], [t2.b], [t2.c]), partitions(p0) Outline Data: ------------------------------------- /*+ BEGIN_OUTLINE_DATA LEADING(@"SEL$1" ("test.t1"@"SEL$1" "test.t2"@"SEL$1" )) USE_MERGE(@"SEL$1" ("test.t2"@"SEL$1" )) PQ_DISTRIBUTE(@"SEL$1" ("test.t2"@"SEL$1" ) LOCAL LOCAL) FULL(@"SEL$1" "test.t1"@"SEL$1") FULL(@"SEL$1" "test.t2"@"SEL$1") END_OUTLINE_DATA */
使用 ODC 查看执行计划示例
使用
EXPLAIN BASIC命令展示执行计划。
使用
EXPLAIN命令展示执行计划。
使用
EXPLAIN EXTENDED命令展示执行计划。
使用
EXPLAIN EXTENDED_NOADDR命令展示执行计划。
使用
EXPLAIN OUTLINE命令可以显示 Outline 信息。
