huaxingao commented on code in PR #10659:
URL: https://github.com/apache/iceberg/pull/10659#discussion_r1683657327
##########
spark/v3.5/spark/src/main/java/org/apache/iceberg/spark/source/SparkScan.java:
##########
@@ -175,7 +184,37 @@ public Statistics estimateStatistics() {
protected Statistics estimateStatistics(Snapshot snapshot) {
// its a fresh table, no data
if (snapshot == null) {
- return new Stats(0L, 0L);
+ return new Stats(0L, 0L, Collections.emptyMap());
+ }
+
+ boolean cboEnabled =
+ Boolean.parseBoolean(spark.conf().get(SQLConf.CBO_ENABLED().key(),
"false"));
+ Map<NamedReference, ColumnStatistics> colStatsMap = null;
+ if (readConf.enableColumnStats() && cboEnabled) {
+ colStatsMap = Maps.newHashMap();
+ List<StatisticsFile> files = table.statisticsFiles();
+ if (!files.isEmpty()) {
+ List<BlobMetadata> metadataList = (files.get(0)).blobMetadata();
+
+ for (BlobMetadata blobMetadata : metadataList) {
+ int id = blobMetadata.fields().get(0);
Review Comment:
I can't find detailed documentation for `BlobMetadata` in the spec. My
understanding is that for the blob type `apache-datasketches-theta-v1`, `ndv`
is required. I assume that `ndv` is set in the `properties` as shown in the
following example. If my assumption is correct, it seems to me that we can only
have one field in the `fields`, establishing a one-to-one relationship with the
`ndv` in the properties.
```
new GenericBlobMetadata(
APACHE_DATASKETCHES_THETA_V1,
snapshotId,
1,
ImmutableList.of(1),
ImmutableMap.of("ndv", "4"))
```
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