[fix](split)Fixed the bug that batch mode split could not query data …

…in multiple be scenarios. (#46218)

### What problem does this PR solve?
Problem Summary:
In multiple be scenarios, batch mode split sometimes could not query
data.

The reason is that the estimated `numApproximateSplits()` may be
relatively small, and the value after dividing the current number of be
may be 0. As a result, the split will not be distributed to be, and the
query result will be empty.
We need to take the max of the value after division and 1.

fe/fe-core/src/main/java/org/apache/doris/datasource/FileQueryScanNode.java

@@ -340,7 +340,10 @@ public void createScanRangeLocations() throws UserException {
             totalFileSize = fileSplit.getLength() * selectedSplitNum;
             long maxWaitTime = ConnectContext.get().getSessionVariable().getFetchSplitsMaxWaitTime();
             // Not accurate, only used to estimate concurrency.
-            int numSplitsPerBE = numApproximateSplits() / backendPolicy.numBackends();
+            // Here, we must take the max of 1, because
+            // in the case of multiple BEs, `numApproximateSplits() / backendPolicy.numBackends()` may be 0,
+            // and finally numSplitsPerBE is 0, resulting in no data being queried.
+            int numSplitsPerBE = Math.max(numApproximateSplits() / backendPolicy.numBackends(), 1);
             for (Backend backend : backendPolicy.getBackends()) {
                 SplitSource splitSource = new SplitSource(backend, splitAssignment, maxWaitTime);
                 splitSources.add(splitSource);