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Comment:Add documentation for the fts3/4/5 remove_diacritic options.
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SHA3-256:34f973966af70008ac21ee9df18e7bd2b497cc53be81025113ae90843f195e7a
User & Date: dan 2019-02-11 13:21:49
Context
2019-02-11
13:24
Fix "asterix" typo in fts5.in. check-in: 569262e571 user: dan tags: trunk
13:21
Add documentation for the fts3/4/5 remove_diacritic options. check-in: 34f973966a user: dan tags: trunk
2019-02-08
16:06
The change of removing deprecated PRAGMAs with SQLITE_OMIT_DEPRECATED was backed out, so remove it from the change log. check-in: 0ed8a559a1 user: drh tags: trunk
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Changes to pages/fts3.in.

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  Unicode61 works very much like "simple" except that it does simple unicode
  case folding according to rules in Unicode Version 6.1 and it recognizes
  unicode space and punctuation characters and uses those to separate tokens.
  The simple tokenizer only does case folding of ASCII characters and only
  recognizes ASCII space and punctuation characters as token separators.

<p>
  By default, "unicode61" also removes all diacritics from Latin script
  characters. This behaviour can be overridden by adding the tokenizer argument
  "remove_diacritics=0". For example:

<codeblock>
    <i>-- Create tables that remove diacritics from Latin script characters</i>
    <i>-- as part of tokenization.</i>
    CREATE VIRTUAL TABLE txt1 USING fts4(tokenize=unicode61);
    CREATE VIRTUAL TABLE txt2 USING fts4(tokenize=unicode61 "remove_diacritics=1");

    <i>-- Create a table that does not remove diacritics from Latin script</i>
    <i>-- characters as part of tokenization.</i>
    CREATE VIRTUAL TABLE txt3 USING fts4(tokenize=unicode61 "remove_diacritics=0");
</codeblock>












<p>
  It is also possible to customize the set of codepoints that unicode61 treats
  as separator characters. The "separators=" option may be used to specify one
  or more extra characters that should be treated as separator characters, and
  the "tokenchars=" option may be used to specify one or more extra characters
  that should be treated as part of tokens instead of as separator characters.







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  Unicode61 works very much like "simple" except that it does simple unicode
  case folding according to rules in Unicode Version 6.1 and it recognizes
  unicode space and punctuation characters and uses those to separate tokens.
  The simple tokenizer only does case folding of ASCII characters and only
  recognizes ASCII space and punctuation characters as token separators.

<p>
  By default, "unicode61" attempts to remove diacritics from Latin script
  characters. This behaviour can be overridden by adding the tokenizer argument
  "remove_diacritics=0". For example:

<codeblock>
    <i>-- Create tables that remove <b>all</b>diacritics from Latin script characters</i>
    <i>-- as part of tokenization.</i>
    CREATE VIRTUAL TABLE txt1 USING fts4(tokenize=unicode61);
    CREATE VIRTUAL TABLE txt2 USING fts4(tokenize=unicode61 "remove_diacritics=2");

    <i>-- Create a table that does not remove diacritics from Latin script</i>
    <i>-- characters as part of tokenization.</i>
    CREATE VIRTUAL TABLE txt3 USING fts4(tokenize=unicode61 "remove_diacritics=0");
</codeblock>

<p>The remove_diacritics option may be set to "0", "1" or "2". The default
   value is "1".  If it is set to "1" or "2", then diacritics are removed from
   Latin script characters as described above. However, if it is set to "1",
   then diacritics are not removed in the fairly uncommon case where a single
   unicode codepoint is used to represent a character with more that one
   diacritic. For example, diacritics are not removed from codepoint 0x1ED9
   ("LATIN SMALL LETTER O WITH CIRCUMFLEX AND DOT BELOW"). This is technically
   a bug, but cannot be fixed without creating backwards compatibility
   problems. If this option is set to "2", then diacritics are correctly
   removed from all Latin characters.

<p>
  It is also possible to customize the set of codepoints that unicode61 treats
  as separator characters. The "separators=" option may be used to specify one
  or more extra characters that should be treated as separator characters, and
  the "tokenchars=" option may be used to specify one or more extra characters
  that should be treated as part of tokens instead of as separator characters.

Changes to pages/fts5.in.

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<p> Any arguments following "unicode61" in the token specification are treated
as a list of alternating option names and values. Unicode61 supports the
following options:

<table striped=1>
  <tr><th> Option <th> Usage
  <tr><td> remove_diacritics
  <td>This option should be set to "0" or "1". If it is set (the default),
  diacritics are removed from all latin script characters as described above.
  If it is clear, they are not. 







  <tr><td> categories
  <td>This option may be used to modify the set of Unicode general categories
  that are considered to correspond to token characters. The argument must
  consist of a space separated list of two-character general category
  abbreviations (e.g. "Lu" or "Nd"), or of the same with the second character
  replaced with an asterix ("*"), interpreted as a glob pattern. The default







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<p> Any arguments following "unicode61" in the token specification are treated
as a list of alternating option names and values. Unicode61 supports the
following options:

<table striped=1>
  <tr><th> Option <th> Usage
  <tr><td> remove_diacritics
  <td>This option should be set to "0", "1" or "2". The default value is "1".
  If it is set to "1" or "2", then diacritics are removed from Latin script
  characters as described above. However, if it is set to "1", then diacritics
  are not removed in the fairly uncommon case where a single unicode codepoint
  is used to represent a character with more that one diacritic. For example,
  diacritics are not removed from codepoint 0x1ED9 ("LATIN SMALL LETTER O WITH
  CIRCUMFLEX AND DOT BELOW"). This is technically a bug, but cannot be fixed
  without creating backwards compatibility problems. If this option is set to
  "2", then diacritics are correctly removed from all Latin characters.

  <tr><td> categories
  <td>This option may be used to modify the set of Unicode general categories
  that are considered to correspond to token characters. The argument must
  consist of a space separated list of two-character general category
  abbreviations (e.g. "Lu" or "Nd"), or of the same with the second character
  replaced with an asterix ("*"), interpreted as a glob pattern. The default