gfphoenix78 commented on code in PR #1241:
URL: https://github.com/apache/cloudberry/pull/1241#discussion_r2253221002
##########
src/backend/access/appendonly/appendonlyam.c:
##########
@@ -1118,6 +1118,311 @@ getNextBlock(AppendOnlyScanDesc scan)
return true;
}
+static int
+appendonly_locate_target_segment(AppendOnlyScanDesc scan, int64 targrow)
+{
+ int64 rowcount;
+
+ for (int i = scan->aos_segfiles_processed - 1; i <
scan->aos_total_segfiles; i++)
+ {
+ if (i < 0)
+ continue;
+
+ rowcount = scan->aos_segfile_arr[i]->total_tupcount;
+ if (rowcount <= 0)
+ continue;
+
+ if (scan->aos_segfile_arr[i]->state ==
AOSEG_STATE_AWAITING_DROP)
+ {
+ /* skip this segment, it is awaiting drop */
+ continue;
+ }
+
+ if (scan->segfirstrow + rowcount - 1 >= targrow)
+ {
+ /* found the target segment */
+ return i;
+ }
+
+ /* continue next segment */
+ scan->segfirstrow += rowcount;
+ scan->segrowsprocessed = 0;
+ }
+
+ /* row is beyond the total number of rows in the relation */
+ return -1;
+}
+
+/*
+ * returns the segfile number in which `targrow` locates
+ */
+static int
+appendonly_getsegment(AppendOnlyScanDesc scan, int64 targrow)
+{
+ int segidx, segno;
+
+ /* locate the target segment */
+ segidx = appendonly_locate_target_segment(scan, targrow);
+ if (segidx < 0)
+ {
+ CloseScannedFileSeg(scan);
+
+ /* done reading all segfiles */
+ Assert(scan->aos_done_all_segfiles);
+
+ return -1;
+ }
+
+ if (segidx + 1 > scan->aos_segfiles_processed)
+ {
+ /* done current segfile */
+ CloseScannedFileSeg(scan);
+ /*
+ * Adjust aos_segfiles_processed to guide
+ * SetNextFileSegForRead() opening next
+ * right segfile.
+ */
+ scan->aos_segfiles_processed = segidx;
+ }
+
+ segno = scan->aos_segfile_arr[segidx]->segno;
+ Assert(segno > InvalidFileSegNumber && segno <=
AOTupleId_MaxSegmentFileNum);
Review Comment:
The value of InvalidFileSegNumber should not be assumed -1.
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