[Bug]fix the crash of checksum task apache#3735 (apache#3738)

1. the table include key column of double/float type
2. when run checksum task, will use all of key columns to compare
3. schema.column(idx) of double/float type is NULL

apache#3735

Author: marising

be/src/olap/row.h

@@ -187,6 +187,12 @@ void agg_finalize_row(const std::vector<uint32_t>& ids, RowType* row, MemPool* m
 template<typename RowType>
 uint32_t hash_row(const RowType& row, uint32_t seed) {
     for (uint32_t cid : row.schema()->column_ids()) {
+        FieldType type = row.schema()->column(cid)->type();
+        // The approximation of float/double in a certain precision range, the binary of byte is not
+        // a fixed value, so these two types are ignored in calculating hash code.
+        if (type == OLAP_FIELD_TYPE_FLOAT || type == OLAP_FIELD_TYPE_DOUBLE) {
+            continue;
+        }
         seed = row.schema()->column(cid)->hash_code(row.cell(cid), seed);
     }
     return seed;

be/src/olap/task/engine_checksum_task.cpp

@@ -80,13 +80,7 @@ OLAPStatus EngineChecksumTask::_compute_checksum() {
         }
     }
 
-    // ignore float and double type considering to precision lose
     for (size_t i = 0; i < tablet->tablet_schema().num_columns(); ++i) {
-        FieldType type = tablet->tablet_schema().column(i).type();
-        if (type == OLAP_FIELD_TYPE_FLOAT || type == OLAP_FIELD_TYPE_DOUBLE) {
-            continue;
-        }
-
         reader_params.return_columns.push_back(i);
     }
 
@@ -118,8 +112,8 @@ OLAPStatus EngineChecksumTask::_compute_checksum() {
             OLAP_LOG_WARNING("fail to read in reader. [res=%d]", res);
             return res;
         }
-
-        row_checksum = hash_row(row, row_checksum);
+        // The value of checksum is independent of the sorting of data rows.
+        row_checksum ^= hash_row(row, 0);
         // the memory allocate by mem pool has been copied,
         // so we should release memory immediately
         mem_pool->clear();