| 1 | <?php
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| 2 | require_once RDFAPI_INCLUDE_DIR . 'sparql/SparqlEngineDb/SqlMerger.php';
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| 3 |
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| 4 | /**
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| 5 | * Determines the offset in a row of sql queries.
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| 6 | *
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| 7 | * @author Christian Weiske <cweiske@cweiske.de>
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| 8 | * @license http://www.gnu.org/licenses/lgpl.html LGPL
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| 9 | *
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| 10 | * @package sparql
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| 11 | */
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| 12 | class SparqlEngineDb_Offsetter
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| 13 | {
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| 14 | public function __construct(ADOConnection $dbConn, Query $query)
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| 15 | {
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| 16 | $this->dbConn = $dbConn;
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| 17 | $this->query = $query;
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| 18 | }//public function __construct(ADOConnection $dbConn, Query $query)
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| 19 |
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| 20 |
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| 21 |
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| 22 | /**
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| 23 | * Determines the offset in the sqls, the position to start form.
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| 24 | *
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| 25 | * @param array $arSqls Array of SQL query parts as returned by
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| 26 | * SparqlEngine_TypeSorter::getOrderifiedSqls()
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| 27 | * @return array Array of two values: The first determines the
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| 28 | * index of the sql query to begin with, the second
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| 29 | * is the row offset that should be used in the final
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| 30 | * SQL query.
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| 31 | */
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| 32 | public function determineOffset($arSqls)
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| 33 | {
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| 34 | $arSM = $this->query->getSolutionModifier();
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| 35 | if ($arSM['offset'] === null) {
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| 36 | return array(0, 0);
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| 37 | }
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| 38 |
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| 39 | $nCount = 0;
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| 40 | foreach ($arSqls as $nId => $arSql) {
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| 41 | $nCurrentCount = $this->getCount($arSql);
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| 42 | if ($nCurrentCount + $nCount > $arSM['offset']) {
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| 43 | return array($nId, $arSM['offset'] - $nCount);
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| 44 | }
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| 45 | $nCount += $nCurrentCount;
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| 46 | }
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| 47 | //nothing found - no results for this offset
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| 48 | return array(count($arSqls), 0);
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| 49 | }//public function determineOffset($arSql)
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| 50 |
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| 51 |
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| 52 |
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| 53 | /**
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| 54 | * Returns the number of rows that the given query will return.
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| 55 | *
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| 56 | * @param array $arSql Array with sql parts and at least keys
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| 57 | * 'from' and 'where' set.
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| 58 | * @return int Number of rows returned.
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| 59 | */
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| 60 | protected function getCount($arSql)
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| 61 | {
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| 62 | $sql = SparqlEngineDb_SqlMerger::getCount($this->query, $arSql);
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| 63 | $dbResult = $this->dbConn->execute($sql);
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| 64 |
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| 65 | $nCount = 0;
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| 66 | foreach ($dbResult as $row) {
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| 67 | $nCount = intval($row[0]);
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| 68 | break;
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| 69 | }
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| 70 | return $nCount;
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| 71 | }//protected function getCount($arSql)
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| 72 |
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| 73 |
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| 74 |
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| 75 | /**
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| 76 | * Creates a sql LIMIT statement if the sparql query needs one.
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| 77 | * This method is needed because AdoDb does not support limits with
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| 78 | * prepared statements. It's a pity.
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| 79 | *
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| 80 | * @return string SQL command to be appended to a query, to limit
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| 81 | * the number of result rows returned.
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| 82 | */
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| 83 | public static function getLimitSql(Query $query, ADOConnection $dbConn)
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| 84 | {
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| 85 | $arSM = $query->getSolutionModifier();
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| 86 | if ($arSM['limit'] === null && $arSM['offset'] === null) {
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| 87 | return '';
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| 88 | }
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| 89 | //this here is mysql syntax. if anyone has problems, write it
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| 90 | //dependent on $dbConn's type
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| 91 | if ($arSM['offset'] === null) {
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| 92 | return ' LIMIT ' . $arSM['limit'];
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| 93 | } else if ($arSM['limit'] === null) {
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| 94 | return ' LIMIT ' . $arSM['offset'] . ', 18446744073709551615';
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| 95 | } else {
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| 96 | return ' LIMIT ' . $arSM['offset'] . ', ' . $arSM['limit'];
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| 97 | }
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| 98 | }//public static function getLimitSql(Query $query, ADOConnection $dbConn)
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| 99 |
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| 100 | }//class SparqlEngineDb_Offsetter
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| 101 |
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| 102 | ?> |
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