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Overview
| Comment: | Further tweaks to the matchinfo() documentation. |
|---|---|
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
d0b390051efa281509f92579723eadaa |
| User & Date: | drh 2015-06-17 16:05:57 |
Context
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2015-06-19
| ||
| 18:57 | Fix an error in fts5.in. check-in: 8f8e1e988f user: dan tags: trunk | |
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2015-06-17
| ||
| 16:05 | Further tweaks to the matchinfo() documentation. check-in: d0b390051e user: drh tags: trunk | |
| 15:59 | Update the change log. Better fragments for matchinfo() flags. check-in: dcccfa67e1 user: drh tags: trunk | |
Changes
Changes to pages/fts3.in.
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docs_with_hits = array[3 * (c + p*cols) + 2]
</pre>
<tr><td>y<td style="white-space:nowrap"><i>cols</i> * <i>phrases</i>
<td><tcl>hd_fragment matchinfo-y {matchinfo y flag}</tcl>
For each distinct combination of a phrase and table column, the
number of usable phrase matches that appear in the column. This is
usually identical to the first value in each set of three returned by the
'x' directive (see above). However, the number of hits reported by the
'y' directive is zero for any phrase that is part of a sub-expression
that does not match the current row. This makes a difference for
expressions that contain AND operators that are descendants of OR
operators. For example, consider the expression:
<pre>
a OR (b AND c)
</pre>
and the document:
<pre>
"a c d"
</pre>
The 'x' directive would report a single hit for the phrases "a" and "c".
However, the 'y' directive reports the number of hits for "c" as zero, as
it is part of a sub-expression that does not match the document - (b AND c).
For queries that do not contain AND operators descended from OR
operators, the result values returned by 'y' are always the same as
those returned by 'x'.
<p style="margin-left:0;margin-right:0">
................................................................................
(phrase 0). The values corresponding to other column/phrase combinations
may be located using the following formula:
<pre>
hits_for_phrase_p_column_c = array[c + p*cols]
</pre>
For queries that use OR expressions, or those that use LIMIT or return
many rows, the 'y' matchinfo option may incur significantly less overhead
than 'x'.
<tr><td>b<td style="white-space:nowrap"><i>(cols+31)/32</i> * <i>phrases</i>
<td><tcl>hd_fragment matchinfo-b {matchinfo b flag}</tcl>
The matchinfo 'b' flag provides similar information to the
[matchinfo 'y' flag], but in a more
compact form. Instead of the precise number of hits, 'b' provides a single
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docs_with_hits = array[3 * (c + p*cols) + 2]
</pre>
<tr><td>y<td style="white-space:nowrap"><i>cols</i> * <i>phrases</i>
<td><tcl>hd_fragment matchinfo-y {matchinfo y flag}</tcl>
For each distinct combination of a phrase and table column, the
number of usable phrase matches that appear in the column. This is
usually identical to the first value in each set of three returned by the
[matchinfo 'x' flag]. However, the number of hits reported by the
'y' flag is zero for any phrase that is part of a sub-expression
that does not match the current row. This makes a difference for
expressions that contain AND operators that are descendants of OR
operators. For example, consider the expression:
<pre>
a OR (b AND c)
</pre>
and the document:
<pre>
"a c d"
</pre>
The [matchinfo 'x' flag] would report a single hit for the phrases "a" and "c".
However, the 'y' directive reports the number of hits for "c" as zero, as
it is part of a sub-expression that does not match the document - (b AND c).
For queries that do not contain AND operators descended from OR
operators, the result values returned by 'y' are always the same as
those returned by 'x'.
<p style="margin-left:0;margin-right:0">
................................................................................
(phrase 0). The values corresponding to other column/phrase combinations
may be located using the following formula:
<pre>
hits_for_phrase_p_column_c = array[c + p*cols]
</pre>
For queries that use OR expressions, or those that use LIMIT or return
many rows, the 'y' matchinfo option may be faster than 'x'.
<tr><td>b<td style="white-space:nowrap"><i>(cols+31)/32</i> * <i>phrases</i>
<td><tcl>hd_fragment matchinfo-b {matchinfo b flag}</tcl>
The matchinfo 'b' flag provides similar information to the
[matchinfo 'y' flag], but in a more
compact form. Instead of the precise number of hits, 'b' provides a single
|