Github user zellerh commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/255#discussion_r49407306
--- Diff: core/sql/src/main/java/org/trafodion/sql/HTableClient.java ---
@@ -421,29 +839,140 @@ else if (versions > 0)
else
numColsInScan = 0;
if (colNamesToFilter != null) {
- FilterList list = new FilterList(FilterList.Operator.MUST_PASS_ALL);
-
- for (int i = 0; i < colNamesToFilter.length; i++) {
- byte[] colName = (byte[])colNamesToFilter[i];
- byte[] coByte = (byte[])compareOpList[i];
- byte[] colVal = (byte[])colValuesToCompare[i];
-
- if ((coByte == null) || (colVal == null)) {
- return false;
- }
-
- String coStr = new String(coByte);
- CompareOp co = CompareOp.valueOf(coStr);
-
- SingleColumnValueFilter filter1 =
- new SingleColumnValueFilter(getFamily(colName),
getName(colName),
- co, colVal);
- list.addFilter(filter1);
- }
-
+ FilterList list;
+ boolean narrowDownResultColumns = false; //to check if we need
a narrow down column filter (V2 only feature)
+ if (compareOpList == null)return false;
+ if (new String((byte[])compareOpList[0]).equals("V2")){ // are
we dealing with predicate pushdown V2
+ list = new
FilterList(FilterList.Operator.MUST_PASS_ALL);
+ HashMap<String,Object> columnsToRemove = new
HashMap<String,Object>();
+ //if columnsToRemove not null, we are narrowing down
using the SingleColumnValue[Exclude]Filter method
+ //else we will use the explicit FamilyFilter and
QualifierFilter
+ //the simplified logic is that we can use the first
method if and only if each and every column in the
+ //pushed down predicate shows up only once.
+ for (int i = 0; i < colNamesToFilter.length; i++) {
+ byte[] colName = (byte[])colNamesToFilter[i];
+
+ // check if the filter column is already part of the
column list, if not add it if we are limiting columns (not *)
+ if(columns!=null && columns.length > 0){// if not *
+ boolean columnAlreadyIn = false; //assume column not
yet in the scan object
+ for (int k=0; k<columns.length;k++){
+ if (Arrays.equals(colName,
(byte[])columns[k])){
+ columnAlreadyIn = true;//found
already exist
+ break;//no need to look further
+ }
+ }
+ if (!columnAlreadyIn){// column was not already in,
so add it
+
scan.addColumn(getFamily(colName),getName(colName));
+ narrowDownResultColumns = true; //since we
added a column for predicate eval, we need to remove it later out of result set
+ String strColName = new String(colName);
+ if (columnsToRemove != null &&
columnsToRemove.containsKey(strColName)){// if we already added this column, it
means it shows up more than once
+ columnsToRemove = null; // therefore,
use the FamilyFilter/QualifierFilter method
+ }else if (columnsToRemove != null)// else
+ columnsToRemove.put(strColName,null);
// add it to the list of column that should be nuked with the Exclude version
of the SingleColumnValueFilter
+ }
+ }
+ }
+ if (columnsToRemove != null)
+ { //we are almost done checking if Exclude version of
SingleColumnnValueFilter can be used. Th elast check s about to know if there
is a IS_NULL_NULL
+ //operation that cannot be using the Exclude method, as
it is transformed in a filterList with OR, therefore we cannot guaranty that
the SingleColumnValueExcludeFilter
+ //performing the exclusion will be reached.
+ boolean is_null_nullFound = false;
+ for (Object o:compareOpList ){
+ if (new
String((byte[])o).equals("IS_NULL_NULL")){
+ is_null_nullFound = true;
+ break;
+ }
+ }
+ if (is_null_nullFound){
+ columnsToRemove = null; // disable Exclude
method version of SingleColumnnValueFilter
+ }else
+ narrowDownResultColumns = false; // we will use
the Exclude version of SingleColumnnValueFilter, so bypass the
Family/QualifierFilter method
+ }
+ Filter f
=constructV2Filter(colNamesToFilter,compareOpList,colValuesToCompare,
columnsToRemove);
+ if (f==null) return false; // error logging done inside
constructV2Filter
+ list.addFilter(f);
+ }//end V2
+ else{// deal with V1
+ list = new FilterList(FilterList.Operator.MUST_PASS_ALL);
+
+ for (int i = 0; i < colNamesToFilter.length; i++) {
+ byte[] colName = (byte[])colNamesToFilter[i];
+ byte[] coByte = (byte[])compareOpList[i];
+ byte[] colVal = (byte[])colValuesToCompare[i];
+
+ if ((coByte == null) || (colVal == null)) {
+ return false;
+ }
+ String coStr = new String(coByte);
+ CompareOp co = CompareOp.valueOf(coStr);
+
+ SingleColumnValueFilter filter1 =
+ new SingleColumnValueFilter(getFamily(colName),
getName(colName),
+ co, colVal);
+ list.addFilter(filter1);
+ }
+ }//end V1
+ // if we added a column for predicate eval, we need to filter down
result columns
+ FilterList resultColumnsOnlyFilter = null;
+ if (narrowDownResultColumns){
+ HashMap<String,ArrayList<byte[]>> hm = new
HashMap<String,ArrayList<byte[]>>(3);//use to deal with multiple family table
+ // initialize hm with list of columns requested for output
+ for (int i=0; i<columns.length; i++){ // if we are here
we know columns is not null
+ if (hm.containsKey(new
String(getFamily((byte[])columns[i])))){
+ hm.get(new
String(getFamily((byte[])columns[i]))).add((byte[])columns[i]);
+ }else{
+ ArrayList<byte[]> al = new
ArrayList<byte[]>();
+ al.add((byte[])columns[i]);
+ hm.put(new
String(getFamily((byte[])columns[i])), al);
+ }
+ }
+
+ if (hm.size()==1){//only one column family
+ resultColumnsOnlyFilter = new
FilterList(FilterList.Operator.MUST_PASS_ALL);
--- End diff --
I made this comment because I don't see the code reducing the "columns"
list. Instead, as far as I can tell, it will add one QualifierFilter for every
column in "columns" - maybe I missed something. For a table with n columns,
that is n**2 filter evaluations for every row, could get expensive. Also, do we
have enough information to tell which columns are required by the scan (after
applying filters)? I would have thought that requires a second list of columns
as input.
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