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14 | 14 | alink="#0000ff">
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15 | 15 | <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
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16 | 16 |
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17 |
| - <P>Last updated: Sat Feb 2 16:46:36 EST 2002</P> |
| 17 | + <P>Last updated: Tue Feb 12 12:14:52 EST 2002</P> |
18 | 18 |
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19 | 19 | <P>Current maintainer: Bruce Momjian (<A href=
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20 | 20 | "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
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@@ -119,6 +119,9 @@ <H2 align="center">Operational Questions</H2>
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119 | 119 | <SMALL>SERIAL</SMALL> insert?<BR>
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120 | 120 | <A href="#4.15.3">4.15.3</A>) Don't <I>currval()</I> and
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121 | 121 | <I>nextval()</I> lead to a race condition with other users?<BR>
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| 122 | + <A href="#4.15.4">4.15.4</A>) Why aren't my sequence numbers reused |
| 123 | + on transaction abort? Why are there gaps in the numbers of my |
| 124 | + sequence/SERIAL column?<BR> |
122 | 125 | <A href="#4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is a
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123 | 126 | <SMALL>TID</SMALL>?<BR>
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124 | 127 | <A href="#4.17">4.17</A>) What is the meaning of some of the terms
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@@ -1092,6 +1095,15 @@ <H4><A name="4.15.3">4.15.3</A>) Don't <I>currval()</I> and
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1092 | 1095 | <P>No. Currval() returns the current value assigned by your
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1093 | 1096 | backend, not by all users.</P>
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1094 | 1097 |
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| 1098 | + <H4><A name="4.15.4">4.15.4</A>) Why aren't my sequence numbers reused |
| 1099 | + on transaction abort? Why are there gaps in the numbers of my |
| 1100 | + sequence/SERIAL column?</H4> |
| 1101 | + |
| 1102 | + <P>To improve concurrency, sequence values are given out to running |
| 1103 | + transactions as needed and are now <i>locked</i> until the |
| 1104 | + transaction completes. This causes gaps in numbering from aborted |
| 1105 | + transactions. |
| 1106 | + |
1095 | 1107 | <H4><A name="4.16">4.16</A>) What is an <SMALL>OID</SMALL>? What is
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1096 | 1108 | a <SMALL>TID</SMALL>?</H4>
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1097 | 1109 |
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