[BugFix] Reject bloom_filter_columns on a column with an ngram index in the lake fast path

A column may carry at most one of {plain bloom filter, ngram bloom filter}. The
regular schema-change path enforces this via IndexAnalyzer.analyseBfWithNgramBf,
but the lake bloom_filter_columns fast path (tryBuildLakeAddBloomFilterJob) did
not — so 'SET ("bloom_filter_columns"="c")' on a column that already has an
NGRAMBF index was silently accepted instead of erroring 'should only have one
bloom filter index or ngram bloom filter index'. Run the same validation before
taking the fast path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: meegoo <meegoo.sr@gmail.com>

Author: meegoo

fe/fe-core/src/main/java/com/starrocks/alter/SchemaChangeHandler.java

@@ -2374,6 +2374,20 @@ public AlterJobV2 analyzeAndCreateJob(List<AlterClause> alterClauses, Database d
             if (bfDelta != null) {
                 AlterJobV2 fastPathJob = null;
                 if (bfDelta.isPureAdd()) {
+                    // A column may carry at most one of {plain bloom filter, ngram
+                    // bloom filter}. The regular schema-change path enforces this
+                    // via IndexAnalyzer.analyseBfWithNgramBf; the fast path must
+                    // too, otherwise SET ("bloom_filter_columns"=...) on a column
+                    // that already has an NGRAMBF index is silently accepted.
+                    Set<ColumnId> addedBfColumnIds = Sets.newTreeSet(ColumnId.CASE_INSENSITIVE_ORDER);
+                    for (String columnName : bfDelta.added) {
+                        Column bfColumn = olapTable.getColumn(columnName);
+                        if (bfColumn != null) {
+                            addedBfColumnIds.add(bfColumn.getColumnId());
+                        }
+                    }
+                    IndexAnalyzer.analyseBfWithNgramBf(olapTable, new HashSet<>(olapTable.getIndexes()),
+                            addedBfColumnIds);
                     fastPathJob = tryBuildLakeAddBloomFilterJob(db, olapTable, bfDelta.added);
                 } else if (bfDelta.isPureDrop()) {
                     fastPathJob = tryBuildLakeDropBloomFilterJob(db, olapTable, bfDelta.dropped);