window多个oracle查版本,Oracle SQL多版本VERSION_COUNT产生的可能性
Oracle SQL多版本VERSION_COUNT产生的可能性
Oracle数据库中执行的SQL,很多时候会因为种种原因产生多个不同的执行版本,一个游标的版本过多很容易引起数据库的性能问题,甚至故障。
有时候一个SQL的版本数量可能多达数万个,以下是我之前在恩墨讲堂分享过的一个案例。
产生SQL多版本的原因很多,通过如下的一些测试我们可以稍微来看看如何分析和找到可能的原因。
以下作为一个基础测试数据,一条基本的SQL查询:
create table t1(c1 int, c2 nvarchar2(100));
alter system flush shared_pool;
var b1 number;
var b2 varchar2(10);
exec :b1 := 1;
exec :b2 := '0';
select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
如果我们修改了优化器参数、环境变量、绑定变量等,都可能使得SQL发生重新解析,产生不同的子游标,也就是不同的VERSION。
SQL> set serveroutput on
SQL> set echo on
SQL> drop table t1 purge;
Table dropped.
SQL> create table t1(c1 int, c2 nvarchar2(100));
Table created.
SQL> alter system flush shared_pool;
System altered.
SQL> var b1 number;
SQL> var b2 varchar2(10);
SQL> exec :b1 := 1;
PL/SQL procedure successfully completed.
SQL> exec :b2 := '0';
PL/SQL procedure successfully completed.
SQL> select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
no rows selected
Rem 这里我们修改了NLS_SORT参数,再来查看SQL的游标数。
SQL> alter session set nls_sort = 'SCHINESE_RADICAL_M';
Session altered.
SQL> select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
no rows selected
SQL> exec shared_cursor('3yr4fwqux2buz')
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000088F64328
CHILD_NUMBER = 0
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000087AE2D38
CHILD_NUMBER = 1
LANGUAGE_MISMATCH = Y
--------------------------------------------------
REM 注意,以上第一个Child就是因为语言不匹配产生的(LANGUAGE_MISMATCH)
REM 以下修改了优化器模式,又一个新的子游标将会因此而产生。
SQL> alter session set optimizer_mode = first_rows;
Session altered.
SQL> select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
no rows selected
SQL> exec shared_cursor('3yr4fwqux2buz')
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000088F64328
CHILD_NUMBER = 0
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000087AE2D38
CHILD_NUMBER = 1
LANGUAGE_MISMATCH = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 000000008A1B2678
CHILD_NUMBER = 2
OPTIMIZER_MODE_MISMATCH = Y
--------------------------------------------------
REM 可以看到,第二个子游标是因为优化器模式不匹配产生的,OPTIMIZER_MODE_MISMATCH.
REM 以下步骤,我们绑定了不同长度的绑定变量,由此又可能产生新的SQL版本。
SQL> var b2 varchar2(2000);
SQL> exec :b2 := '0';
PL/SQL procedure successfully completed.
SQL> select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
no rows selected
SQL> exec shared_cursor('3yr4fwqux2buz')
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000088F64328
CHILD_NUMBER = 0
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000087AE2D38
CHILD_NUMBER = 1
LANGUAGE_MISMATCH = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 000000008A1B2678
CHILD_NUMBER = 2
OPTIMIZER_MODE_MISMATCH = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 00000000876C6E38
CHILD_NUMBER = 3
BIND_LENGTH_UPGRADEABLE = Y
--------------------------------------------------
REM 我们看到的第三个子游标就是因为绑定变量长度不同而产生的。
从Oracle 9i开始,Oracle对中文语言方式(Simplified Chinese和Traditional Chinese)提供了多种排序方式。主要由以下四种,大家可以进行修改尝试:
SCHINESE_RADICAL_M 针对简体中文,按照部首(第一顺序)、笔划(第二顺序)排序
SCHINESE_STROKE_M 针对简体中文,按照笔划(第一顺序)、部首(第二顺序)排序
SCHINESE_PINYIN_M 针对简体中文,按照拼音排序
TCHINESE_RADICAL_M 针对繁体中文,按照部首(第一顺序)、笔划(第二顺序)排序
TCHINESE_STROKE_M 针对繁体中文,按照笔划(第一顺序)、部首(第二顺序)排序
当然可以逐一尝试:
SQL> alter session set nls_sort = 'TCHINESE_RADICAL_M';
Session altered.
SQL> select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2;
no rows selected
SQL> exec shared_cursor('3yr4fwqux2buz')
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000088F64328
CHILD_NUMBER = 0
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000087AE2D38
CHILD_NUMBER = 1
LANGUAGE_MISMATCH = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 000000008A1B2678
CHILD_NUMBER = 2
OPTIMIZER_MODE_MISMATCH = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 00000000876C6E38
CHILD_NUMBER = 3
BIND_LENGTH_UPGRADEABLE = Y
--------------------------------------------------
SQL_TEXT = select /* test */ * from t1 where c1 = :b1 and c2 = :b2 order by c2
SQL_ID = 3yr4fwqux2buz
ADDRESS = 0000000088361678
CHILD_ADDRESS = 0000000087AD8AB0
CHILD_NUMBER = 4
LANGUAGE_MISMATCH = Y
--------------------------------------------------
以上测试是基于11.2.0.3版本,在Oracle 12c中,相关的可能因素已经多达64个,参考官方手册可以了解 V$SQL_SHARED_CURSOR 的更详细信息。
文中用到的shared_cursor存储过程脚本列举如下:
create or replace PROCEDURE shared_cursor(
p_sqlid IN VARCHAR2 ) AUTHID CURRENT_USER
IS
l_theCursor NUMBER;
col_cnt NUMBER;
col_rec dbms_sql.desc_tab;
col_value VARCHAR2(4000);
ret_val NUMBER;
BEGIN
l_theCursor := dbms_sql.open_cursor;
dbms_sql.parse(l_theCursor, 'select sql.sql_text, cur.*
from v$sql_shared_cursor cur, v$sql sql
where cur.sql_id = sql.sql_id
and cur.child_number = sql.child_number
and sql.sql_id = :p_sqlid', dbms_sql.native);
dbms_sql.bind_variable( l_theCursor, ':p_sqlid', p_sqlid );
dbms_sql.describe_columns(l_theCursor, col_cnt, col_rec);
FOR idx IN 1 .. col_cnt
LOOP
dbms_sql.define_column(l_theCursor, idx, col_value, 4000);
END LOOP;
ret_val := dbms_sql.execute(l_theCursor);
WHILE(dbms_sql.fetch_rows(l_theCursor) > 0)
LOOP
FOR idx IN 1 .. col_cnt
LOOP
dbms_sql.column_value(l_theCursor, idx, col_value);
IF col_rec(idx).col_name IN ('SQL_ID', 'ADDRESS', 'CHILD_ADDRESS', 'CHILD_NUMBER', 'SQL_TEXT') THEN
dbms_output.put_line(rpad(col_rec(idx).col_name, 30) || ' = ' || col_value);
elsif col_value = 'Y' THEN
dbms_output.put_line(rpad(col_rec(idx).col_name, 30) || ' = ' || col_value);
END IF;
END LOOP;
dbms_output.put_line('--------------------------------------------------');
END LOOP;
dbms_sql.close_cursor(l_theCursor);
END;
转引Oracle 12.1的V$SQL_SHARED_CURSOR说明,列举如下,供参考。
V$SQL_SHARED_CURSOR explains why a particular child cursor is not shared with existing child cursors. Each column identifies a specific reason why the cursor cannot be shared.
ColumnDatatypeDescription
SQL_ID
VARCHAR2(13)
SQL identifier
ADDRESS
RAW(4 | 8)
Address of the parent cursor
CHILD_ADDRESS
RAW(4 | 8)
Address of the child cursor
CHILD_NUMBER
NUMBER
Child number
UNBOUND_CURSOR
VARCHAR2(1)
(Y|N) The existing child cursor was not fully built (in other words, it was not optimized)
SQL_TYPE_MISMATCH
VARCHAR2(1)
(Y|N) The SQL type does not match the existing child cursor
OPTIMIZER_MISMATCH
VARCHAR2(1)
(Y|N) The optimizer environment does not match the existing child cursor
OUTLINE_MISMATCH
VARCHAR2(1)
(Y|N) The outlines do not match the existing child cursor
STATS_ROW_MISMATCH
VARCHAR2(1)
(Y|N) The existing statistics do not match the existing child cursor
LITERAL_MISMATCH
VARCHAR2(1)
(Y|N) Non-data literal values do not match the existing child cursor
FORCE_HARD_PARSE
VARCHAR2(1)
(Y|N) For internal use
EXPLAIN_PLAN_CURSOR
VARCHAR2(1)
(Y|N) The child cursor is an explain plan cursor and should not be shared
BUFFERED_DML_MISMATCH
VARCHAR2(1)
(Y|N) Buffered DML does not match the existing child cursor
PDML_ENV_MISMATCH
VARCHAR2(1)
(Y|N) PDML environment does not match the existing child cursor
INST_DRTLD_MISMATCH
VARCHAR2(1)
(Y|N) Insert direct load does not match the existing child cursor
SLAVE_QC_MISMATCH
VARCHAR2(1)
(Y|N) The existing child cursor is a slave cursor and the new one was issued by the coordinator (or, the existing child cursor was issued by the coordinator and the new one is a slave cursor)
TYPECHECK_MISMATCH
VARCHAR2(1)
(Y|N) The existing child cursor is not fully optimized
AUTH_CHECK_MISMATCH
VARCHAR2(1)
(Y|N) Authorization/translation check failed for the existing child cursor
BIND_MISMATCH
VARCHAR2(1)
(Y|N) The bind metadata does not match the existing child cursor
DESCRIBE_MISMATCH
VARCHAR2(1)
(Y|N) The typecheck heap is not present during the describe for the child cursor
LANGUAGE_MISMATCH
VARCHAR2(1)
(Y|N) The language handle does not match the existing child cursor
TRANSLATION_MISMATCH
VARCHAR2(1)
(Y|N) The base objects of the existing child cursor do not match
BIND_EQUIV_FAILURE
VARCHAR2(1)
(Y|N) The bind value's selectivity does not match that used to optimize the existing child cursor
INSUFF_PRIVS
VARCHAR2(1)
(Y|N) Insufficient privileges on objects referenced by the existing child cursor
INSUFF_PRIVS_REM
VARCHAR2(1)
(Y|N) Insufficient privileges on remote objects referenced by the existing child cursor
REMOTE_TRANS_MISMATCH
VARCHAR2(1)
(Y|N) The remote base objects of the existing child cursor do not match
LOGMINER_SESSION_MISMATCH
VARCHAR2(1)
(Y|N) LogMiner Session parameters mismatch
INCOMP_LTRL_MISMATCH
VARCHAR2(1)
(Y|N) Cursor might have some binds (literals) which may be unsafe/non-data. Value mismatch.
OVERLAP_TIME_MISMATCH
VARCHAR2(1)
(Y|N) Mismatch caused by setting session parameter ERROR_ON_OVERLAP_TIME
EDITION_MISMATCH
VARCHAR2(1)
(Y|N) Cursor edition mismatch
MV_QUERY_GEN_MISMATCH
VARCHAR2(1)
(Y|N) Internal, used to force a hard-parse when analyzing materialized view queries
USER_BIND_PEEK_MISMATCH
VARCHAR2(1)
(Y|N) Cursor is not shared because value of one or more user binds is different and this has a potential to change the execution plan
TYPCHK_DEP_MISMATCH
VARCHAR2(1)
(Y|N) Cursor has typecheck dependencies
NO_TRIGGER_MISMATCH
VARCHAR2(1)
(Y|N) Cursor and child have no trigger mismatch
FLASHBACK_CURSOR
VARCHAR2(1)
(Y|N) Cursor non-shareability due to flashback
ANYDATA_TRANSFORMATION
VARCHAR2(1)
(Y|N) Is criteria for opaque type transformation and does not match
PDDL_ENV_MISMATCH
VARCHAR2(1)
(Y|N) Environment setting mismatch for parallel DDL cursor (that is, one or more of the following parameter values have changed: PARALLEL_EXECUTION_ENABLED, PARALLEL_DDL_MODE, PARALLEL_DDL_FORCED_DEGREE, orPARALLEL_DDL_FORCED_INSTANCES)
TOP_LEVEL_RPI_CURSOR
VARCHAR2(1)
(Y|N) Is top level RPI cursor
DIFFERENT_LONG_LENGTH
VARCHAR2(1)
(Y|N) Value of LONG does not match
LOGICAL_STANDBY_APPLY
VARCHAR2(1)
(Y|N) Logical standby apply context does not match
DIFF_CALL_DURN
VARCHAR2(1)
(Y|N) If Slave SQL cursor/single call
BIND_UACS_DIFF
VARCHAR2(1)
(Y|N) One cursor has bind UACs and one does not
PLSQL_CMP_SWITCHS_DIFF
VARCHAR2(1)
(Y|N) PL/SQL anonymous block compiled with different PL/SQL compiler switches
CURSOR_PARTS_MISMATCH
VARCHAR2(1)
(Y|N) Cursor was compiled with subexecution (cursor parts were executed)
STB_OBJECT_MISMATCH
VARCHAR2(1)
(Y|N) STB is an internal name for a SQL Management Object Mismatch. A SQL Management Object Mismatch means that either a SQL plan baseline, or a SQL profile, or a SQL patch has been created for your SQL statement between the executions. Because a cursor is a read-only entity, a hard parse is forced to be able to create a new cursor that contains information about the new SQL management object related to this SQL statement.
CROSSEDITION_TRIGGER_MISMATCH
VARCHAR2(1)
(Y|N) The set of crossedition triggers to execute might differ
PQ_SLAVE_MISMATCH
VARCHAR2(1)
(Y|N) Top-level slave decides not to share cursor
TOP_LEVEL_DDL_MISMATCH
VARCHAR2(1)
(Y|N) Is top-level DDL cursor
MULTI_PX_MISMATCH
VARCHAR2(1)
(Y|N) Cursor has multiple parallelizers and is slave-compiled
BIND_PEEKED_PQ_MISMATCH
VARCHAR2(1)
(Y|N) Cursor based around bind peeked values
MV_REWRITE_MISMATCH
VARCHAR2(1)
(Y|N) Cursor needs recompilation because an SCN was used during compile time due to being rewritten by materialized view
ROLL_INVALID_MISMATCH
VARCHAR2(1)
(Y|N) Marked for rolling invalidation and invalidation window exceeded
OPTIMIZER_MODE_MISMATCH
VARCHAR2(1)
(Y|N) Parameter OPTIMIZER_MODE mismatch (for example, all_rows versus first_rows_1)
PX_MISMATCH
VARCHAR2(1)
(Y|N) Mismatch in one parameter affecting the parallelization of a SQL statement. For example, one cursor was compiled with parallel DML enabled while the other was not.
MV_STALEOBJ_MISMATCH
VARCHAR2(1)
(Y|N) Cursor cannot be shared because there is a mismatch in the list of materialized views which were stale when the cursor was built
FLASHBACK_TABLE_MISMATCH
VARCHAR2(1)
(Y|N) Cursor cannot be shared because there is a mismatch with triggers being enabled and/or referential integrity constraints being deferred
LITREP_COMP_MISMATCH
VARCHAR2(1)
(Y|N) Mismatch in use of literal replacement
PLSQL_DEBUG
VARCHAR2(1)
(Y|N) Value of the PLSQL_DEBUG parameter for the current session does not match the value used to build the cursor
LOAD_OPTIMIZER_STATS
VARCHAR2(1)
(Y|N) A hard parse is forced to initialize extended cursor sharing
ACL_MISMATCH
VARCHAR2(1)
(Y|N) Cached ACL evaluation result stored in the child cursor is not valid for the current session or user
FLASHBACK_ARCHIVE_MISMATCH
VARCHAR2(1)
(Y|N) Value of the FLASHBACK_DATA_ARCHIVE_INTERNAL_CURSOR parameter for the current session does not match the value used to build the cursor
LOCK_USER_SCHEMA_FAILED
VARCHAR2(1)
(Y|N) User or schema used to build the cursor no longer exists
Note: This sharing criterion is deprecated
REMOTE_MAPPING_MISMATCH
VARCHAR2(1)
(Y|N) Reloaded cursor was previously remote-mapped and is currently not remote-mapped. Therefore, the cursor must be reparsed.
LOAD_RUNTIME_HEAP_FAILED
VARCHAR2(1)
(Y|N) Loading of run-time heap for the new cursor (or reload of aged out cursor) failed
HASH_MATCH_FAILED
VARCHAR2(1)
(Y|N) No existing child cursors have the unsafe literal bind hash values required by the current cursor
PURGED_CURSOR
VARCHAR2(1)
(Y|N) Child cursor is marked for purging
BIND_LENGTH_UPGRADEABLE
VARCHAR2(1)
(Y|N) Bind length(s) required for the current cursor are longer than the bind length(s) used to build the child cursor
USE_FEEDBACK_STATS
VARCHAR2(1)
(Y|N) A hard parse is forced so that the optimizer can reoptimize the query with improved optimizer inputs (for example, cardinality estimates)
REASON
CLOB
Child number, id, and reason the cursor is not shared. The content of this column is structured using XML.
CON_ID
NUMBER
The ID of the container to which the data pertains. Possible values include:
0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs.
1: This value is used for rows containing data that pertain to only the root
n: Where n is the applicable container ID for the rows containing data
By eygle on 2015-09-25 13:21 |
Comments (0) |
HowTo | 3184 |
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