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Doc: Tweak description of B-Tree duplicate tuples. 

Defining duplicates as "close by" to each other was unclear.  Simplify
the definition.

Backpatch: 13-, where deduplication was introduced (by commit 0d861bbb)
This commit is contained in:
Peter Geoghegan 2020-06-20 17:34:07 -07:00
parent 3be015c9fc
commit 48c6959864
1 changed files with 4 additions and 4 deletions
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doc/src/sgml/btree.sgml
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@ -635,10 +635,10 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns
A duplicate is a leaf page tuple (a tuple that points to a table A duplicate is a leaf page tuple (a tuple that points to a table
row) where <emphasis>all</emphasis> indexed key columns have values row) where <emphasis>all</emphasis> indexed key columns have values
that match corresponding column values from at least one other leaf that match corresponding column values from at least one other leaf
page tuple that's close by in the same index. Duplicate tuples are page tuple in the same index. Duplicate tuples are quite common in
quite common in practice. B-Tree indexes can use a special, practice. B-Tree indexes can use a special, space-efficient
space-efficient representation for duplicates when an optional representation for duplicates when an optional technique is
technique is enabled: <firstterm>deduplication</firstterm>. enabled: <firstterm>deduplication</firstterm>.
</para> </para>
<para> <para>
Deduplication works by periodically merging groups of duplicate Deduplication works by periodically merging groups of duplicate