Optimize Excel GetOrCreateRow: reduce loops

for ( size_t nFrom = maRowMap.size(); nFrom <= nXclRow; ++nFrom )

This previous code worked best under the assumption
that every row is added to the map. However, the size of the
map actually has no correlation to the row numbers contained in it
when many rows are identical to each other (think silly formatting
and empty rows - related to tdf#105840)
Thus row 1,000,000 could occupy slot 2, and every access of that row
would then trigger nearly 1 million redundant loops.

Optimize:
-check to see if the row already exists - if so do nothing.
-existance of higher rows indicates there are no missing rows.
-build missing rows from the previously-mapped row.

Change-Id: Ib02520a1bf0f77b5ca0ec5ad3165ff7ea879515f
Reviewed-on: https://gerrit.libreoffice.org/34038
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Bartosz Kosiorek <gang65@poczta.onet.pl>

1 files changed, 21 insertions, 8 deletions

diff --git a/sc/source/filter/excel/xetable.cxx b/sc/source/filter/excel/xetable.cxx
index a8627c0571e6..0c573e973f1e 100644
--- a/sc/source/filter/excel/xetable.cxx
+++ b/sc/source/filter/excel/xetable.cxx
@@ -2375,18 +2375,31 @@ void XclExpRowBuffer::SaveXml( XclExpXmlStream& rStrm )
 
 XclExpRow& XclExpRowBuffer::GetOrCreateRow( sal_uInt32 nXclRow, bool bRowAlwaysEmpty )
 {
-    RowMap::iterator itr = maRowMap.begin();
-    ScDocument& rDoc = GetRoot().GetDoc();
-    SCTAB nScTab = GetRoot().GetCurrScTab();
-    for ( size_t nFrom = maRowMap.size(); nFrom <= nXclRow; ++nFrom )
+    RowMap::iterator itr = maRowMap.lower_bound( nXclRow );
+    const bool bFound = itr != maRowMap.end();
+    // bFoundHigher: nXclRow was identical to the previous entry, so not explicitly created earlier
+    const bool bFoundHigher = bFound && itr != maRowMap.find( nXclRow );
+    if( !bFound || bFoundHigher )
     {
-        itr = maRowMap.find(nFrom);
-        if ( itr == maRowMap.end() )
+        size_t nFrom = 0;
+        if( itr != maRowMap.begin() )
+        {
+            --itr;
+            if( bFoundHigher )
+                nFrom = nXclRow;
+            else
+                nFrom = itr->first + 1;
+        }
+
+        const ScDocument& rDoc = GetRoot().GetDoc();
+        const SCTAB nScTab = GetRoot().GetCurrScTab();
+        // create the missing rows first
+        while( nFrom <= nXclRow )
         {
             // only create RowMap entries if it is first row in spreadsheet,
             // if it is the desired row, for rows that height differ from previous,
             // if row is collapsed, has outline level (tdf#100347), or row is hidden (tdf#98106).
-            bool bHidden = rDoc.RowHidden(nFrom, nScTab);
+            const bool bHidden = rDoc.RowHidden(nFrom, nScTab);
             // Always get the actual row height even if the manual size flag is
             // not set, to correctly export the heights of rows with wrapped
             // texts.
@@ -2403,11 +2416,11 @@ XclExpRow& XclExpRowBuffer::GetOrCreateRow( sal_uInt32 nXclRow, bool bRowAlwaysE
                 RowRef p(new XclExpRow(GetRoot(), nFrom, maOutlineBfr, bRowAlwaysEmpty, bHidden, nHeight));
                 maRowMap.insert(RowMap::value_type(nFrom, p));
             }
+            ++nFrom;
         }
     }
     itr = maRowMap.find(nXclRow);
     return *itr->second;
-
 }
 
 // Cell Table