Snippets generation: add method for generating from doc stored text. Still needs refining, esp. for phrase/near

src/sampleconf/recoll.conf

@@ -214,7 +214,7 @@ membermaxkbs = 50000
 
 
 # <grouptitle id="TERMS">Parameters affecting how we generate
-# terms</grouptitle> 
+# terms and organize the index</grouptitle> 
 
 # Changing some of these parameters will imply a full
 # reindex. Also, when using multiple indexes, it may not make sense
@@ -231,6 +231,21 @@ membermaxkbs = 50000
 # implies an index reset.</descr></var>
 indexStripChars = 1
 
+# <var name="indexStoreRawText" type="bool"><brief>Decide if we store the
+# documents' text content in the index.</brief><descr>Storing the text
+# allows extracting snippets from it at query time, 
+# instead of building them from index position data. This Has become
+# necessary for versions of Xapian 1.6, which have dropped support
+# for the chert index format, and adopted a setup which renders our
+# use of positions list unacceptably slow in cases. 'raw' text here
+# means that the text is not stripped of upper-case, diacritics, or
+# punctuation signs. It is still translated from its original format
+# to UTF-8 plain text. This increases the index size by 10-20% typically,
+# but also allows for nicer snippets, so it may be worth enabling it even
+# if not strictly needed for performance if you can afford the space.
+# </desc></var>
+indexStoreRawText = 0
+
 # <var name="nonumbers" type="bool"><brief>Decides if terms will be
 # generated for numbers.</brief><descr>For example "123", "1.5e6",
 # 192.168.1.4, would not be indexed if nonumbers is set ("value123" would