Merge pull request #773 from dolthub/perf/restore-cache-on-fastpath

Restore eager payload cache on the no-mutmap Next fast-path

Author: timsehn

src/prolly_btree.c

@@ -5257,6 +5257,23 @@ static int prollyBtCursorNext(BtCursor *pCur, int flags){
     if( rc==SQLITE_OK ){
       if( pCur->pCur.eState==PROLLY_CURSOR_VALID ){
         pCur->eState = CURSOR_VALID;
+        /* Pre-populate the payload cache for INTKEY clean-read scans
+        ** (same idea as PR #770, restored on Tim's no-mutmap fast
+        ** path). xPayloadSize then xPayloadFetch are both called per
+        ** row during OP_Column / table scans; both go through
+        ** getCursorPayload's multi-branch chain. Caching the
+        ** (pData, nData) pair here makes both subsequent trips hit
+        ** the early-return at the top of getCursorPayload. The
+        ** pointer borrows the leaf node memory; CLEAR_CACHED_PAYLOAD
+        ** on the next move keeps it valid for exactly one row. */
+        if( pCur->curIntKey ){
+          const u8 *pVal; int nVal;
+          cursorCurrentTreeValue(pCur, &pVal, &nVal);
+          if( nVal > 0 ){
+            pCur->pCachedPayload = (u8*)pVal;
+            pCur->nCachedPayload = nVal;
+          }
+        }
       } else {
         pCur->eState = CURSOR_INVALID;
         return SQLITE_DONE;