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Posted to dev@hive.apache.org by Sohan Jain <so...@fb.com> on 2011/07/01 00:24:01 UTC
Review Request: HIVE-2246: Dedupe tables' column schemas from partitions in
the metastore db
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/985/
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Review request for hive.
Summary
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We can re-organize the JDO models to reduce space usage to keep the metastore scalable for the future. Currently, partitions are the fastest growing objects in the metastore, and the metastore keeps a separate copy of the columns list for each partition. We can normalize the metastore db by decoupling Columns from Storage Descriptors and not storing duplicate lists of the columns for each partition.
An idea is to create an additional level of indirection with a "Column Descriptor" that has a list of columns. A table has a reference to its latest Column Descriptor (note: a table may have more than one Column Descriptor in the case of schema evolution). Partitions and Indexes can reference the same Column Descriptors as their parent table.
Currently, the COLUMNS table in the metastore has roughly (number of partitions + number of tables) * (average number of columns pertable) rows. We can reduce this to (number of tables) * (average number of columns per table) rows, while incurring a small cost proportional to the number of tables to store the Column Descriptors.
This addresses bug HIVE-2246.
https://issues.apache.org/jira/browse/HIVE-2246
Diffs
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trunk/metastore/if/hive_metastore.thrift 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MColumnDescriptor.java PRE-CREATION
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MDatabase.java 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MFieldSchema.java 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MIndex.java 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MPartition.java 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MStorageDescriptor.java 1140399
trunk/metastore/src/model/org/apache/hadoop/hive/metastore/model/MTable.java 1140399
trunk/metastore/src/model/package.jdo 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/exec/DDLTask.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/index/TableBasedIndexHandler.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/index/bitmap/BitmapIndexHandler.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/index/compact/CompactIndexHandler.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/metadata/MetaDataFormatUtils.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/metadata/Partition.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/metadata/Table.java 1140399
trunk/ql/src/java/org/apache/hadoop/hive/ql/parse/ImportSemanticAnalyzer.java 1140399
Diff: https://reviews.apache.org/r/985/diff
Testing
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Haven't run any unit tests yet, just qualitative testing so far.
Thanks,
Sohan