Query operations of hsqldb source code analysis series query Engines

The query process is parsed like insert. The final call is the getSingleResult method of the QuerySpecification class below. RangeVariable is the [java] private Result getSingleResult (Session session, int maxRows) related to the query conditions) {int [] limits = sortAndSlice. getLimits (session, this, maxRows); Result r = buildResult (session, limits); RowSetNavigatorData navigator = (RowSetNavigatorData) r. getNavigator (); if (isDistinctSelect) {navigator. removeDuplicates (session);} if (so RtAndSlice. hasOrder () {navigator. sortOrder (session);} if (limits! = SortAndSlice. defaultLimits &&! SortAndSlice. skipFullResult) {navigator. trim (limits [0], limits [1]);} return r;} private Result buildResult (Session session, int [] limits) {RowSetNavigatorData navigator = new RowSetNavigatorData (session, (QuerySpecification) this); Result result = Result. newResult (navigator); result. metaData = resultMetaData; if (isUpdatable) {result. rsProperties = ResultProperties. updatablePropsValue;} int s KipCount = 0; int limitCount = limits [2]; if (sortAndSlice. skipFullResult) {skipCount = limits [0]; limitCount = limits [1];} if (this. isSimpleCount) {Object [] data = new Object [indexLimitData]; Table table = rangeVariables [0]. getTable (); table. materialise (session); PersistentStore = table. getRowStore (session); long count = store. elementCount (session); data [0] = data [indexStartAggregates] = ValuePool. getLong (count); navigator. add (data); return result;} int fullJoinIndex = 0; RangeIterator [] rangeIterators = new RangeIterator [rangeVariables. length]; for (int I = 0; I <rangeVariables. length; I ++) {rangeIterators [I] = rangeVariables [I]. getIterator (session);} session. sessionContext. rownum = 1; for (int currentIndex = 0;) {if (currentIndex <fullJoinIndex) {// finished current s Pan // or finished outer rows on right navigator boolean end = true; for (int I = fullJoinIndex + 1; I <rangeVariables. length; I ++) {if (rangeVariables [I]. isRightJoin) {fullJoinIndex = I; currentIndex = I; end = false; (RangeIteratorRight) rangeIterators [I]). setOnOuterRows (); break ;}} if (end) {break ;}} RangeIterator it = rangeIterators [currentIndex]; if (it. next () {if (currentIndex <RangeVariables. length-1) {currentIndex ++; continue ;}} else {it. reset (); currentIndex --; continue;} if (limitCount = 0) {break;} session. sessionData. startRowProcessing (); Object [] data = new Object [indexLimitData]; for (int I = 0; I <indexStartAggregates; I ++) {if (isAggregated & aggresponcheck [I]) {continue;} else {data [I] = exprColumns [I]. getValue (session) ;}}for (int I = indexL ImitVisible; I <indexLimitRowId; I ++) {if (I = indexLimitVisible) {data [I] = it. getRowidObject ();} else {data [I] = it. getCurrentRow () ;}} session. sessionContext. rownum ++; if (skipCount> 0) {skipCount --; continue;} Object [] groupData = null; if (isAggregated | isGrouped) {groupData = navigator. getGroupData (data); if (groupData! = Null) {data = groupData ;}}for (int I = indexStartAggregates; I <indexLimitExpressions; I ++) {data [I] = exprColumns [I]. updateAggregatingValue (session, data [I]);} if (groupData = null) {navigator. add (data);} else if (isAggregated) {navigator. update (groupData, data);} int rowCount = navigator. getSize (); if (rowCount = session. resultMaxMemoryRows &&! IsAggregated &&! IsSingleMemoryTable) {navigator = new RowSetNavigatorDataTable (session, this, navigator); result. setNavigator (navigator);} if (isAggregated | isGrouped) {if (! SortAndSlice. isGenerated) {continue ;}}if (rowCount >= limitCount) {break ;}} navigator. reset (); for (int I = 0; I <rangeVariables. length; I ++) {rangeIterators [I]. reset ();} if (! IsGrouped &&! IsAggregated) {return result;} if (isAggregated) {if (! IsGrouped & navigator. getSize () = 0) {Object [] data = new Object [exprColumns. length]; for (int I = 0; I <indexStartAggregates; I ++) {if (! Aggresponcheck [I]) {data [I] = exprColumns [I]. getValue (session) ;}} navigator. add (data);} navigator. reset (); session. sessionContext. setRangeIterator (navigator); while (navigator. next () {Object [] data = navigator. getCurrent (); for (int I = indexStartAggregates; I <indexLimitExpressions; I ++) {data [I] = exprColumns [I]. getAggregatedValue (session, data [I]) ;}for (int I = 0; I <indexStartAggrega Tes; I ++) {if (aggresponcheck [I]) {data [I] = exprColumns [I]. getValue (session) ;}} session. sessionContext. unsetRangeIterator (navigator);} navigator. reset (); if (havingCondition! = Null) {while (navigator. hasNext () {Object [] data = (Object []) navigator. getNext (); if (! Boolean. TRUE. equals (data [indexLimitVisible + groupByColumnCount]) {navigator. remove () ;}} navigator. reset ();} return result;} For example, for a like operation, the query result is: This StatementQuery is really complicated, so you can understand it later.