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Commitfc9b645

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Update disk space computation because oids are now optional.
1 parent14720f7 commitfc9b645

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lines changed

2 files changed

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‎doc/FAQ

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Frequently Asked Questions (FAQ) for PostgreSQL
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Last updated: ThuAug 11 09:21:58 EDT 2005
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Last updated: ThuSep 1 12:17:52 EDT 2005
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Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
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twenty bytes in length. The flat file would be 2.8 MB. The size of the
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PostgreSQL database file containing this data can be estimated as 6.4
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MB:
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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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Indexes do not require as much overhead, but do contain the data that
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is being indexed, so they can be large also.

‎doc/src/FAQ/FAQ.html

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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: ThuAug 11 09:21:58 EDT 2005</P>
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<P>Last updated: ThuSep 1 12:17:52 EDT 2005</P>
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<P>Current maintainer: Bruce Momjian (<Ahref=
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"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)
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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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