ctas 與create table後insert

時間 2020-03-29

標籤 ctas create table insert 欄目 SQL 简体版

原文原文鏈接

下面是測試結論，此結論只是在本測試環境有效。

1，ctas與create table後insert語句產生的redo是差很少的。

2，ctas生成的undo遠遠小於create table and insert方式。

3，ctas生成的undo與create table後insert /*+ append */差很少。

4，ctas nologging方法生成的log遠遠小於其它的方式。

5，append方式並不必定能減小redo的生成，可是確定能減小undo的生成。

6，append減小redo，前提是表在nologging方式下面，注意這裏表上面沒有索引，append只對表有效，對索引無效。

下面是詳細的測試步驟

1，ctas方式生成的undo與redo

SQL> SELECT a.name, b.VALUE

2 FROM v$sysstat a, v$mystat b

3 WHERE a.statistic# = b.statistic#

4 AND a.name IN ('redo size', 'undo change vector size');

NAME VALUE

---------------------------------------------------------------- ----------

redo size 0

10. undo change vector size 0

11. SQL> create table scott.test_ctas as select * from dba_objects;

12. SQL> /* Formatted on 2013/3/8 22:07:44 (QP5 v5.240.12305.39476) */

13. SQL> SELECT a.name, b.VALUE

14. 2 FROM v$sysstat a, v$mystat b

15. 3 WHERE a.statistic# = b.statistic#

16. 4 AND a.name IN ('redo size', 'undo change vector size');

17.

18. NAME VALUE

19. ---------------------------------------------------------------- ----------

20. redo size 5794552

21. undo change vector size 23812

22.

23. 2，ctas nologging方式生成的undo與redo

24.

25. SQL> SELECT a.name, b.VALUE

26. 2 FROM v$sysstat a, v$mystat b

27. 3 WHERE a.statistic# = b.statistic#

28. 4 AND a.name IN ('redo size', 'undo change vector size');

29.

30. NAME VALUE

31. ---------------------------------------------------------------- ----------

32. redo size 0

33. undo change vector size 0

34.

35. SQL> create table scott.test_ctas_nologging nologging as select * from dba_objects;

36.

37. Table created.

38.

39. SQL> SELECT a.name, b.VALUE

40. 2 FROM v$sysstat a, v$mystat b

41. 3 WHERE a.statistic# = b.statistic#

42. 4 AND a.name IN ('redo size', 'undo change vector size');

43.

44. NAME VALUE

45. ---------------------------------------------------------------- ----------

46. redo size 88576

47. undo change vector size 22008

48.

49. 這種方式生成的UNDO,REDO的大小都是最好的，

50.

51.

52. 3，普通表與insert生成的undo與redo

53.

54. SQL> SELECT a.name, b.VALUE

55. 2 FROM v$sysstat a, v$mystat b

56. 3 WHERE a.statistic# = b.statistic#

57. 4 AND a.name IN ('redo size', 'undo change vector size');

58.

59. NAME VALUE

60. ---------------------------------------------------------------- ----------

61. redo size 0

62. undo change vector size 0

63.

64. SQL> create table scott.test_normal as select * from dba_objects where 1=0;

65.

66. Table created.

67.

68. SQL> SELECT a.name, b.VALUE

69. 2 FROM v$sysstat a, v$mystat b

70. 3 WHERE a.statistic# = b.statistic#

71. 4 AND a.name IN ('redo size', 'undo change vector size');

72.

73. NAME VALUE

74. ---------------------------------------------------------------- ----------

75. redo size 19848

76. undo change vector size 5712

77.

78. SQL> insert into scott.test_normal select * from dba_objects;

79.

80. 50350 rows created.

81.

82. SQL> SELECT a.name, b.VALUE

83. 2 FROM v$sysstat a, v$mystat b

84. 3 WHERE a.statistic# = b.statistic#

85. 4 AND a.name IN ('redo size', 'undo change vector size');

86.

87. NAME VALUE

88. ---------------------------------------------------------------- ----------

89. redo size 5725444

90. undo change vector size 208092

91.

92.

93. 4，普通create表與insert append方式生成的redo與undo

94. SQL> SELECT a.name, b.VALUE

95. 2 FROM v$sysstat a, v$mystat b

96. 3 WHERE a.statistic# = b.statistic#

97. 4 AND a.name IN ('redo size', 'undo change vector size');

98.

99. NAME VALUE

100. ---------------------------------------------------------------- ----------

101. redo size 0

102. undo change vector size 0

103.

104. SQL> create table scott.test_normal_append as select * from dba_objects where 1=2;

105.

106. Table created.

107.

108. SQL> SELECT a.name, b.VALUE

109. 2 FROM v$sysstat a, v$mystat b

110. 3 WHERE a.statistic# = b.statistic#

111. 4 AND a.name IN ('redo size', 'undo change vector size');

112.

113. NAME VALUE

114. ---------------------------------------------------------------- ----------

115. redo size 21224

116. undo change vector size 6072

117.

118. SQL> insert /*+ append */ into scott.test_normal_append select * from dba_objects;

119.

120. 50350 rows created.

121.

122. SQL> SELECT a.name, b.VALUE

123. 2 FROM v$sysstat a, v$mystat b

124. 3 WHERE a.statistic# = b.statistic#

125. 4 AND a.name IN ('redo size', 'undo change vector size');

126.

127. NAME VALUE

128. ---------------------------------------------------------------- ----------

129. redo size 5771092

130. undo change vector size 21072

131.

132. 5，nologging方式的create表與insert append方式生成的undo與redo

133.

134. SQL> SELECT a.name, b.VALUE

135. 2 FROM v$sysstat a, v$mystat b

136. 3 WHERE a.statistic# = b.statistic#

137. 4 AND a.name IN ('redo size', 'undo change vector size');

138.

139. NAME VALUE

140. ---------------------------------------------------------------- ----------

141. redo size 0

142. undo change vector size 0

143.

144. SQL> create table scott.test_normal_append_nologging nologging as select * from dba_objects where 1=2;

145.

146. Table created.

147.

148. SQL> SELECT a.name, b.VALUE

149. 2 FROM v$sysstat a, v$mystat b

150. 3 WHERE a.statistic# = b.statistic#

151. 4 AND a.name IN ('redo size', 'undo change vector size');

152.

153. NAME VALUE

154. ---------------------------------------------------------------- ----------

155. redo size 37568

156. undo change vector size 14204

157.

158. SQL> insert /*+ append */ into scott.test_normal_append_nologging select * from dba_objects;

159.

160. 50351 rows created.

161.

162. SQL> SELECT a.name, b.VALUE

163. 2 FROM v$sysstat a, v$mystat b

164. 3 WHERE a.statistic# = b.statistic#

165. 4 AND a.name IN ('redo size', 'undo change vector size');

166.

167. NAME VALUE

168. ---------------------------------------------------------------- ----------

169. redo size 142944

170. undo change vector size 46744

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