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Posted to gitbox@hive.apache.org by GitBox <gi...@apache.org> on 2021/07/05 13:20:24 UTC
[GitHub] [hive] szlta commented on a change in pull request #2418: HIVE-25255: Add support for replace columns
szlta commented on a change in pull request #2418:
URL: https://github.com/apache/hive/pull/2418#discussion_r663922844
##########
File path: iceberg/iceberg-catalog/src/main/java/org/apache/iceberg/hive/HiveSchemaUtil.java
##########
@@ -138,22 +137,88 @@ public static Type convert(TypeInfo typeInfo) {
}
/**
- * Produces the difference of two FieldSchema lists by only taking into account the field name and type.
+ * Returns a SchemaDifference containing those fields which are present in only one of the collections, as well as
+ * those fields which are present in both (in terms of the name) but their type or comment has changed.
* @param minuendCollection Collection of fields to subtract from
* @param subtrahendCollection Collection of fields to subtract
- * @return the result list of difference
+ * @param bothDirections Whether or not to compute the missing fields from the minuendCollection as well
+ * @return the difference between the two schemas
*/
- public static Collection<FieldSchema> schemaDifference(
- Collection<FieldSchema> minuendCollection, Collection<FieldSchema> subtrahendCollection) {
+ public static SchemaDifference getSchemaDiff(Collection<FieldSchema> minuendCollection,
+ Collection<FieldSchema> subtrahendCollection, boolean bothDirections) {
+ SchemaDifference difference = new SchemaDifference();
- Function<FieldSchema, FieldSchema> unsetCommentFunc = fs -> new FieldSchema(fs.getName(), fs.getType(), null);
- Set<FieldSchema> subtrahendWithoutComment =
- subtrahendCollection.stream().map(unsetCommentFunc).collect(Collectors.toSet());
+ for (FieldSchema first : minuendCollection) {
+ boolean found = false;
+ for (FieldSchema second : subtrahendCollection) {
+ if (first.getName().equals(second.getName())) {
+ found = true;
+ if (!Objects.equals(first.getType(), second.getType())) {
+ difference.typeChanged(first);
+ }
+ if (!Objects.equals(first.getComment(), second.getComment())) {
+ difference.commentChanged(first);
+ }
+ }
+ }
+ if (!found) {
+ difference.missingFromSecond(first);
+ }
+ }
+
+ if (bothDirections) {
+ SchemaDifference otherWay = getSchemaDiff(subtrahendCollection, minuendCollection, false);
+ otherWay.missingFromSecond().forEach(difference::missingFromFirst);
+ }
- return minuendCollection.stream()
- .filter(fs -> !subtrahendWithoutComment.contains(unsetCommentFunc.apply(fs))).collect(Collectors.toList());
+ return difference;
}
+ public static class SchemaDifference {
+ private final List<FieldSchema> missingFromFirst = new ArrayList<>();
+ private final List<FieldSchema> missingFromSecond = new ArrayList<>();
+ private final List<FieldSchema> typeChanged = new ArrayList<>();
+ private final List<FieldSchema> commentChanged = new ArrayList<>();
+
+ public List<FieldSchema> missingFromFirst() {
Review comment:
I'd rather avoid having an overload for this method that has a very different behavior (get vs add), maybe you could rename either set of these methods to be more descriptive.
##########
File path: iceberg/iceberg-catalog/src/main/java/org/apache/iceberg/hive/HiveSchemaUtil.java
##########
@@ -138,22 +137,88 @@ public static Type convert(TypeInfo typeInfo) {
}
/**
- * Produces the difference of two FieldSchema lists by only taking into account the field name and type.
+ * Returns a SchemaDifference containing those fields which are present in only one of the collections, as well as
+ * those fields which are present in both (in terms of the name) but their type or comment has changed.
* @param minuendCollection Collection of fields to subtract from
* @param subtrahendCollection Collection of fields to subtract
- * @return the result list of difference
+ * @param bothDirections Whether or not to compute the missing fields from the minuendCollection as well
+ * @return the difference between the two schemas
*/
- public static Collection<FieldSchema> schemaDifference(
- Collection<FieldSchema> minuendCollection, Collection<FieldSchema> subtrahendCollection) {
+ public static SchemaDifference getSchemaDiff(Collection<FieldSchema> minuendCollection,
+ Collection<FieldSchema> subtrahendCollection, boolean bothDirections) {
+ SchemaDifference difference = new SchemaDifference();
- Function<FieldSchema, FieldSchema> unsetCommentFunc = fs -> new FieldSchema(fs.getName(), fs.getType(), null);
- Set<FieldSchema> subtrahendWithoutComment =
- subtrahendCollection.stream().map(unsetCommentFunc).collect(Collectors.toSet());
+ for (FieldSchema first : minuendCollection) {
+ boolean found = false;
+ for (FieldSchema second : subtrahendCollection) {
+ if (first.getName().equals(second.getName())) {
Review comment:
Why not use Objects.equals here too?
##########
File path: iceberg/iceberg-handler/src/main/java/org/apache/iceberg/mr/hive/HiveIcebergMetaHook.java
##########
@@ -474,6 +480,43 @@ private static PartitionSpec spec(Configuration configuration, Schema schema, Pr
}
}
+ private void handleReplaceColumns(org.apache.hadoop.hive.metastore.api.Table hmsTable) throws MetaException {
+ HiveSchemaUtil.SchemaDifference schemaDifference = HiveSchemaUtil.getSchemaDiff(hmsTable.getSd().getCols(),
+ HiveSchemaUtil.convert(icebergTable.schema()), true);
+ if (!schemaDifference.isEmpty()) {
+ updateSchema = icebergTable.updateSchema();
+ } else {
+ // we should get here if the user restated the exactly the existing columns in the REPLACE COLUMNS command
+ LOG.info("Found no difference between new and old schema for ALTER TABLE REPLACE COLUMNS for" +
+ " table: {}. There will be no Iceberg commit.", hmsTable.getTableName());
Review comment:
nit: could place an explicit return statement here. In case any future change tweak the code below, someone could miss this path having to yield to a no-op.
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