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@ -10,7 +10,7 @@ |
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alink="#0000ff"> |
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<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> |
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<P>Last updated: Thu Aug 11 09:21:58 EDT 2005</P> |
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<P>Last updated: Thu Sep 1 12:17:52 EDT 2005</P> |
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<P>Current maintainer: Bruce Momjian (<A href= |
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"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>) |
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@ -635,23 +635,23 @@ table?</TD><TD>unlimited</TD></TR> |
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The size of the PostgreSQL database file containing this data can |
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be estimated as 6.4 MB:</P> |
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<PRE> |
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32 bytes: each row header (approximate) |
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28 bytes: each row header (approximate) |
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24 bytes: one int field and one text field |
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+ 4 bytes: pointer on page to tuple |
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---------------------------------------- |
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60 bytes per row |
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56 bytes per row |
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The data page size in PostgreSQL is 8192 bytes (8 KB), so: |
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8192 bytes per page |
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------------------- = 136 rows per database page (rounded down) |
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60 bytes per row |
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------------------- = 146 rows per database page (rounded down) |
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56 bytes per row |
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100000 data rows |
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-------------------- = 735 database pages (rounded up) |
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128 rows per page |
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-------------------- = 685 database pages (rounded up) |
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146 rows per page |
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735 database pages * 8192 bytes per page = 6,021,120 bytes (6 MB) |
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685 database pages * 8192 bytes per page = 5,611,520 bytes (5.6 MB) |
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</PRE> |
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<P>Indexes do not require as much overhead, but do contain the data |
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