DtSearchQuery(library call)											       DtSearchQuery(library call)

NAME

       DtSearchQuery -- Perform a DtSearch database search for a specified query

SYNOPSIS

       #include <Dt/Search.h>
       int DtSearchQuery(
       void *qry,
       char *dbname,
       int search_type,
       char *date1,
       char *date2,
       DtSrResult **results,
       long *resultscount,
       char *stems,
       int *stemcount);

DESCRIPTION

       DtSearchQuery is the DtSearch API search function.

       DtSearchQuery  is  passed a query string and some search options, performs the requested search, and if successful returns a linked list of
       DtSrResult structures representing the documents satisfying the search.

       The results list contains information about the documents that can be used for subsequent retrievals, as well as information  suitable  for
       display to an end user.

   Search Types
       DtSearchQuery supports three types of searches: P, W, and S.

   Type P Search Query Strings
       Query strings for search type P have the simplest syntax, namely a sequence of words separated by ASCII whitespace. Punctuation and invalid
       words are silently discarded by the search engine. The only possible syntax error is that all query words happen to be invalid in the  lan-
       guage of the database.

       Search type P is often used to implement a limited Query-by-Example (QBE) search paradigm. In this scenario, users typically paste document
       text from whatever source into a query string text field. Their expectation is that the search engine will  return  the	documents  in  the
       database  that  are  "most  similar"  to  the text of the query string, and the statistical sort of the results list usually satisfies that
       expectation.

       Note that although search type P does not use boolean syntax, it is actually implemented as a stemmed search (type S search)  with  implied
       boolean ORs between words.

   Types S and W Boolean Query Strings
       Query  strings for search types S (stemmed boolean) and W (exact word boolean) must be syntactically valid boolean expressions as described
       below. Any string that does not match a valid expression rule is invalid and will fail with an error message.

       Query words for all search types may be entered in any codeset for a supported DtSearch language, including multibyte languages. Words  may
       be  identified  as  invalid  by	the  language  module of the database for a number of reasons including any words that would not have been
       indexed because they are too short, too long, on the stop list, etc. With one exception, linguistically invalid words result  in  a  syntax
       error.  The  exception is in the case of an "all ANDs" query, where invalid words and valid words that happen not to be in the database are
       silently erased from the query string.

       The boolean query operators are the ASCII metacharacters: '&' for AND, '|' for OR, '~' for NOT, '(' and ')' for open and close  parentheses
       respectively, and '@ nnn' for collocation expressions.

       All expression tokens are separated by ASCII whitespace. Typically this i 1 or more space or tab characters. Omitting whitespace separators
       is legal if it can be done unambiguously. For example "word1&word2" is a legal expression but "word1word2" would be interpreted as a single
       word token.

       The  ASCII "at" sign (@) marks a special boolean collocation operator. The collocation operator has the syntax "@n...", the ASCII "at" sign
       followed by one or more ASCII numeric digits, representing an integer with value greater than zero. Collocation is a variation of  the  AND
       search  where a user can specify the maximum distance in bytes between any two words. In most languages a byte is equivalent to a character
       position. For example to find "ice" and "cream" separated by no more than five characters, the search query "ice @5  cream"  may  be  used.
       Unlike  other  boolean  operators, the collocation operator can apply only to naked word tokens, not other expressions.	Searches including
       collocation operators are slower than searches without them, and can be much slower for common words.

       There are a maximum of 8 distinct word tokens. Collocation operators count as part of the 8. There is no limit to the number of	operators,
       as long as they match the syntax rules.

	      Note:

	      Collocation  operators  are  only supported for "Austext flavor" databases.  The default flavor of database created by dtsrcreate is
	      "Dtinfo flavor," which does not support collocation.

   Boolean Query Syntax Rules
       There are only 6 syntax rules and the rules are recursive. Ambiguity is resolved by precedence and associativity rules.

	  1. valid_expression := word_token

		 A valid expression can be just a valid naked word token. Semantically, the expression returns all documents containing the speci-
		 fied word. The word_token must be a valid word in the language of the database being searched.

	  2. valid_expression := valid_expression '&' valid_expression

		 The  ASCII  ampersand character is the AND character. Semantically, it returns all documents satisfying both the first and second
		 expressions (boolean intersection). AND is also the "implied" boolean operator in the following  sense:  the  query  parser  will
		 insert  an ampersand between words or expressions that otherwise would be separated only by whitespace. For example "word1 word2"
		 becomes "word1 & word2".

	  3. valid_expression := valid_expression '|' valid_expression

		 The ASCII virgule (vertical slash) character is the OR character. It means return all documents satisfying either  the  first	or
		 the second expression (boolean union).

	  4. valid_expression := '(' valid_expression ')'

		 Valid	expressions may be recursively nested in ASCII open and close parentheses characters. The query parser "forgives" two com-
		 mon human errors.  It will automatically discard excessive close parentheses characters, and it will automatically generate close
		 parentheses  characters if necessary at the end of a query. For example, "aaa | (bbb & ccc)))))) ddd" becomes "aaa | ( bbb & ccc)
		 & ddd", and "aaa ((bbbb" becomes "aaa ( ( bbb ) )".

	  5. valid_expression := '~' valid_expression

		 The ASCII tilde character is the unary NOT operator. It returns every document in the database that is not in the set	satisfying
		 the expression.

	  6. valid_expression := word_token collocation_operator word_token

		 Collocation  operators  are  permitted only between words, not expressions.  Each of the word tokens and the collocation operator
		 itself occupy slots in the table of 8 maximum word tokens.

   Boolean Associativity and Precedence Table
       In order from highest precedence to lowest:

       Associativity   Operator     Example
       (none)	       COLLOC
       right	       NOT	    "aaa~bbb"  resolved   as   "aaa   &
				    (~(bbb)"
       left	       AND	    "aaa  bbb  ccc" resolved as "(aaa &
				    bbb) & ccc"
       left	       OR	    "aaa|bbb|ccc" resolved as  "(aaa  |
				    bbb) | ccc"
       (none)	       naked word

   Example Boolean Queries
       aaa bbb ccc

       Returns all records that contain at least one occurrence of all three words.

       aaa | (bbb ~ccc)

       Retrieves all records containing "aaa" and also all records containing "bbb", but not "ccc".

       aaa ~(aaa @1 bbb)

       Returns all records containing "aaa" but omits those where "aaa" is one character away from "bbb".

       It is possible to formulate a query that requires retrieving all records in the database that contain none of the query words (for example,
       ~aaa. Users should be warned that in a large database such a search can take a very long time.

       Using the implied associativity and precedence rules, the ambiguous query string aaa ~bbb | ccc ~ddd @10 eee is	disambiguated  as  (aaa  &
       (~bbb)) | (ccc & (~(ddd @10 eee))).

ARGUMENTS

       search_type
		 Specifies the type of search to perform. Valid values are P, W, and S.

		 Search  type  P indicates that the query string is a sequence of words separated by ASCII whitespace.	It requests that the words
		 be stemmed prior to searching, that all documents containing any of the words be returned, that the results list be statistically
		 sorted,  and  that  no  more  than  the top MaxResults list items be returned where MaxResults is the current value returned from
		 DtSearchGetMaxResults. Note that a type P search is identical to a type S boolean search  with  an  implied  boolean  OR  between
		 words.

		 Search types W and S are boolean query searches. They indicate that the query string is a sequence of words and boolean operators
		 matching the syntax described under "Types S and W Boolean Query Strings" above.

		 Type S requests that words be stemmed prior to searching. Type 'W' requests that words be left unstemmed. Both types request that
		 all  documents  containing the combinations of query words specified by the boolean operations be returned, that the results list
		 be statistically sorted if possible, and that no more than the top MaxResults list items be returned whereMaxResults is the  cur-
		 rent value returned from DtSearchGetMaxResults.

       dbname	 Specifies  which  database  is  to  be  searched.  It	is  any  one  of  the  database name strings returned from DtSearchInit or
		 DtSearchReinit. If dbname is NULL, the first database name string is used.

		 Within the specified database, searches will be restricted to those documents whose DtSrKeytype.is_selected field is nonzero.

       date1 and date2" 10 Specify a range of document dates to use for the search. Only documents within the specified range will be returned	on
		 the results list.

		 date1 is the older end of the range and if not NULL, requests DtSearch to return only those records younger than (that is, after)
		 the specified date.

		 date2 is the younger end of the range and if not NULL, requests DtSearch to return only those records older than (that is before)
		 the specified date.

		 It is valid to specify just one of the arguments.

		 Undated  documents  always  qualify  for  a  results list regardless of search date strings. The format of a valid date string is
		 described in DtSearchValidDateString(3).

       stems and stemscount" 10 Specify a character buffer to hold parsed and stemmed words and a variable to receive the number of stored  words.
		 stems and stemscount are optional; they can be NULL. However, if either is specified, they must both be specified.

		 If  specified	stemsmust point to a character buffer large enough to hold DtSrMAX_STEMCOUNT by DtSrMAXWIDTH_HWORD bytes. An array
		 of parsed and stemmed query words will be stored here by the API for use by a later call to DtSearchHighlight.

		 The size of the array will be stored in stemscount.

       results and
		 resultscount" 10 Specify where a pointer to the results list will be stored and a variable to receive the number of items on  the
		 list.

		 Results lists can be manipulated with several utility functions.

		 In DtSearch, frequency of occurrence information is maintained for words across the whole database and within documents. For most
		 queries, results lists are sorted by this statistical information and presented to the user as a "proximity" number for each doc-
		 ument	on  the list. Proximity is meant to appear to a user as a distance, or a measure of the nearness of the query to the docu-
		 ment. Conceptually, the smaller the proximity the "closer" the document is to the query and the more likely it will  be  valuable
		 to the user

		 DtSearch  searches  only  one database at a time and returns only results lists for that single database. However, browsers often
		 provide the illusion of simultaneous searches in multiple databases, merging the results lists by proximity when completed. Since
		 the  domain  of knowledge and density of words and records may vary from database to database, the value of proximity numbers may
		 similarly vary, and some databases may be underrepresented on merged results lists.

RETURN VALUE

       This function has three common return codes.

       DtSrOK is returned, as well as a results list and stems array, when the search was completely successful.

       DtSrNOTAVAIL is returned when the query was valid but the search was unsuccessful (that is, no set of documents matched the  query).  There
       are usually no messages with DtSrNOTAVAIL.

       DtSrFAIL  is  returned  when the search was unsuccessful, usually because of an invalid query, and user messages on the MessageList explain
       why.

       Any API function can also return DtSrREINIT and the return codes for fatal engine errors at any time.

SEE ALSO

       DtSrAPI(3),  DtSearchReinit(3),	DtSearchGetMaxResults(3),  DtSearchSetMaxResults(3),  DtSearchGetKeytypes(3),  DtSearchValidDateString(3),
       DtSearchSortResults(3), DtSearchFreeResults(3), DtSearchHighlight(3)

														       DtSearchQuery(library call)