Added the search_generate_text_SQL() function that generates

SQL clauses using documental indexes. Only MySQL for now.
Under 1.8 this isn't used officially (experimental!) but
we need it here right now (won't interfere at all). MDL-8830

Merged from MOODLE_18_STABLE

diff --git a/lib/searchlib.php b/lib/searchlib.php
index 4f74d923e4c372cc692ca40fbcf773935fcbe6ef..964e745ae57c62f8179cfdf7020deb826445d77b 100644 (file)
--- a/lib/searchlib.php
+++ b/lib/searchlib.php
@@ -302,6 +302,128 @@ class search_parser {
     } 
 }
 
+// Primitive function to generate a SQL string from a parse tree
+// using TEXT indexes. If searches aren't suitable to use TEXT
+// this function calls the default search_generate_SQL() one.
+//      
+// $parsetree should be a parse tree generated by a 
+// search_lexer/search_parser combination. 
+// Other fields are database table names to search.
+function search_generate_text_SQL($parsetree, $datafield, $metafield, $mainidfield, $useridfield,
+                             $userfirstnamefield, $userlastnamefield, $timefield, $instancefield) {
+    global $CFG;
+
+/// First of all, search for reasons to switch to standard SQL generation
+/// Only mysql are supported for now
+    if ($CFG->dbfamily != 'mysql') {
+        return search_generate_SQL($parsetree, $datafield, $metafield, $mainidfield, $useridfield,
+                                   $userfirstnamefield, $userlastnamefield, $timefield, $instancefield);
+    }
+
+/// Here we'll acumulate non-textual tokens
+    $non_text_tokens = array();
+
+    $ntokens = count($parsetree);
+    if ($ntokens == 0) {
+        return "";
+    }
+
+    $SQLString = '';
+    $text_sql_string = '';
+
+    $datasearch_clause = '';
+    $metasearch_clause = '';
+
+    foreach ($parsetree as $token) {
+
+        $type = $token->getType();
+        $value = $token->getValue();
+
+        switch($type){
+            case TOKEN_STRING:
+            /// If it's a multiword token, quote it
+                if (strstr($value, ' ')) {
+                    $datasearch_clause .= '"' . $value . '" ';
+            /// Simple word token, search for it as prefix
+                } else {
+                    $datasearch_clause .= $value . '* ';
+                }
+                break;
+            case TOKEN_EXACT:
+            /// token must be exactly as requested
+                $datasearch_clause .= '+' . $value . ' ';
+                break;
+            case TOKEN_NEGATE:
+            /// token must not exist as prefix
+                $datasearch_clause .= '-' . $value . '* ';
+                break;
+            case TOKEN_META:
+            /// token in metafield, search for it as prefix
+                $metasearch_clause .= $value . '* ';
+                break;
+            case TOKEN_USER:
+            case TOKEN_USERID:
+            case TOKEN_INSTANCE:
+            case TOKEN_DATETO:
+            case TOKEN_DATEFROM:
+            /// delegate to standard search
+                $non_text_tokens[] = $token;
+                break;
+            default:
+                return '';
+        }
+    }
+
+/// Call to standard search for pending tokens
+    if (!empty($non_text_tokens)) {
+        $SQLString = search_generate_SQL($non_text_tokens, $datafield, $metafield, $mainidfield, $useridfield,
+                                         $userfirstnamefield, $userlastnamefield, $timefield, $instancefield);
+    }
+/// Build the final SQL clause
+    if (!empty($datasearch_clause)) {
+    /// Must have $datafield to search within
+        if (!empty($datafield)) {
+            $text_sql_string .= 'MATCH (' . $datafield;
+        /// And optionally $metafield
+            if (!empty($metafield)) {
+                $text_sql_string .= ', ' . $metafield;
+            }
+        /// Begin with the AGAINST clause
+            $text_sql_string .= ') AGAINST (' . "'";
+        /// Add the search terms
+            $text_sql_string .= trim($datasearch_clause);
+        /// Close AGAINST clause
+            $text_sql_string .= "' IN BOOLEAN MODE)";
+        }
+    }
+/// Now add the metasearch_clause
+    if (!empty($metasearch_clause)) {
+    /// Must have $metafield to search within
+        if (!empty($metafield)) {
+        /// AND operator if needed
+            if (!empty($text_sql_string)) {
+                $text_sql_string .= ' AND ';
+            }
+            $text_sql_string .= 'MATCH (' . $metafield;
+        /// Begin with the AGAINST clause
+            $text_sql_string .= ') AGAINST (' . "'";
+        /// Add the search terms
+            $text_sql_string .= trim($metasearch_clause);
+        /// Close AGAINST clause
+            $text_sql_string .= "' IN BOOLEAN MODE)";
+        }
+    }
+/// Finally add the non-text conditions
+    if (!empty($SQLString)) {
+    /// AND operator if needed
+        if (!empty($text_sql_string)) {
+            $text_sql_string .= ' AND ';
+        }
+        $text_sql_string .= $SQLString;
+    }
+
+    return $text_sql_string;
+}
 
 // Primitive function to generate a SQL string from a parse tree. 
 // Parameters: