This patch adds the ability to compute and drop column and table
statistics at partition granularity.
The following commands are added. Detail about the implementation
follows.
COMPUTE INCREMENTAL STATS <tbl_name> [PARTITION <partition_spec>]
This variant of COMPUTE STATS will, ultimately, do the same thing as the
traditional COMPUTE STATS statement, but does so by caching the
intermediate state of the computation for each partition in the Hive
MetaStore. If the PARTITION clause is added, the computation is
performed for only that partition. If the PARTITION clause is omitted,
incremental stats are updated only for those partitions with missing
incremental stats (e.g. one column does not have stats, or incremental
stats was never computed for this partition). In this patch, incremental
stats are only invalidated when a DROP STATS variant is executed. Future
patches can automatically invalidate the statistics after REFRESH or
INSERT queries, etc.
DROP INCREMENTAL STATS <tbl_name> PARTITION <part_spec>
This variant of DROP stats removes the incremental statistics for the
given table. It does *not* recalculate the statistics for the whole
table, so this should be used only to invalidate the intermediate state
for a partition which will shortly be subject to COMPUTE INCREMENTAL
STATS. The point of this variant is to allow users to notify Impala when
they believe a partition has changed significantly enough to warrant
recomputation of its statistics. It is not necessary for new partitions;
Impala will detect that they do not have any valid statistics.
--------
This is achieved by adapting the existing HLL UDA via swapping its
finalize method for a new one which returns the intermediate HLL
buckets, rather than aggregating and then disposing of them. This
intermediate state is then returned to Impala's catalog-op-executor.cc,
which then passes the intermediate state back to the frontend to be
ultimately stored in the HMS.
This intermediate state is computed on a per-partition basis by grouping
the input to the UDA by partition. Thus, the incremental computation
produces one row for each partition selected (the set of which might be
quite small, if there are few partitions without valid incremental
stats: this is the point of the new commands).
At the same time, the query coordinator aggregates the output of the UDA
to produce table-level statistics. This computation incorporates any
existing (and not re-computed) intermediate partition state which is
passed to the coordinator by the frontend. The resulting statistics are
saved to the table as normal.
Intermediate statistics are serialised to the HMS by writing a Thrift
structure's serialised form to the partition's 'parameters' map. There
is a schema-imposed limit of 4000 characters to the serialised string,
which is exacerbated by the fact that the Thrift representation must
first be base-64 encoded to avoid type errors in the HMS. The current
patch breaks the encoded structure into 4k chunks, and then recombines
them on read. The alltypes table (11 columns) takes about three of these
chunks. This may mean that incremental stats are not suitable for
particularly wide tables: these structures could be zipped before
encoding for some space savings. In the meantime, the NDV estimates are
run-length encoded (since they are generally sparse); this can result in
substantial space savings.
Change-Id: If82cf4753d19eb532265acb556f798b95fbb0f34
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4475
Tested-by: jenkins
Reviewed-by: Henry Robinson <henry@cloudera.com>
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5408
This patch addresses the following issues:
1. Allow creating Avro tables without col defs in Impala. Compute stats works on them.
2. Handle table creation with inconsistent col defs and Avro schema as follows:
The table creation will succeed and ignore the col defs in favor of the Avro schema.
A warning is issued that the col defs and the Avro schema are inconsistent.
Compute stats works on such tables.
This patch does not address the issue of compute stats after Avro schema evolution.
Change-Id: Iea6b737d238d81491dc2097012ebc149a89d03ba
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4182
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: Alex Behm <alex.behm@cloudera.com>
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4250
Tested-by: jenkins
Syntax is "CREATE TABLE name LIKE fileformat '/path/to/file'".
Supports all options that CREATE TABLE does. Currently only PARQUET is supported.
Run testdata/bin/create-load-data.sh after pulling this patch.
Change-Id: Ibb9fbb89dbde6acceb850b914c48d12f22b33f55
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2720
Reviewed-by: Victor Bittorf <victor.bittorf@cloudera.com>
Tested-by: jenkins
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3158
This fixes the flaky ALTER/CREATE tests by removing a verification step that
didn't add value and was non-deterministic. The verficiation step that was
removed verified that CREATE/ALTER set the appropriate file format by
changing the format to something that didn't match the underlying data files,
then attempting to read the data. This is already covered by the positive
test case where the file format is changed to match the underlying data.
Change-Id: I66f485405234f472f3b83f3e776bf7f2c10de874
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1379
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: jenkins
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1382
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: Lenni Kuff <lskuff@cloudera.com>
This change updates our DDL syntax support to allow for using 'STORED AS PARQUET'
as well as 'STORED AS PARQUETFILE'. Moving forward we should prefer the new syntax,
but continue to support the old. I made the same change for 'AVROFILE', but since
we have not yet documented the 'AVROFILE' syntax I left out support for the old syntax.
Change-Id: I10c73a71a94ee488c9ae205485777b58ab8957c9
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1053
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
This change adds support for cluster-synchronized catalog operations. This provides the
guaranteethat after a catalog op completes, all other subscribers to the catalog topic have
also processed that update. This is useful when load balancing, because a common workflow
is to target a different impalad for each statement executed.
For example if each of the following were executed sequentially, but targeting
a different node:
1) CREATE TABLE Foo
2) INSERT INTO Foo
3) SELECT * FROM Foo
4) INSERT INTO Foo ....
Since both the INSERT and the CREATE update the catalog, it would not work as expected
without this patch. The user might either get a "table not found" error or would be
missing partition information from the INSERT.
The downside is that this approach to DDL takes a bit longer because we need to wait
until all subscribers have processed an update. If all nodes are healthy, this overhead
should not be significantly longer than the current DDL time. However, a single bad node
might slow down or completely block the completion of all DDL operations. By default
this feature is disabled, but it can be enabled using a new query option: SYNCED_DDL=1
To test this, the base test suite was updated to support selecting a random impalad
to execute each query section in a query test file. This is currently only enabled
for the insert and DDL tests, but could be leveraged by more tests in the future.
TODO: Add additional failure tests around this functionality.
TODO: Add an explicit "sync" statement so users do not need to run all their DDL
in this mode (since it is slower).
Change-Id: I45e757a931bf2a4740cc0cdd1e76ce49a1e22b83
Reviewed-on: http://gerrit.ent.cloudera.com:8080/899
Reviewed-by: Ishaan Joshi <ishaan@cloudera.com>
Tested-by: jenkins
Changes MemLimit to MemTracker:
- the limit is optional
- it also records a label and an optional parent
- Consume() and Release() also update the ancestors and there's also a new
AnyLimitExceeded(), which also checks the ancestors
- the consumption counter is a HighwaterMarkCounter and can optionally be created
as part of a profile
Each fragment instance now has a MemTracker that is part of a 3-level
hierarchy: process, query, fragment instance.
Change-Id: I5f580f4956fdf07d70bd9a6531032439aaf0fd07
Reviewed-on: http://gerrit.ent.cloudera.com:8080/339
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: Nong Li <nong@cloudera.com>
This adds support for CREATE TABLE AS SELECT to Impala. It supports all functionality a
regular CREATE TABLE statement includes, except it does not allow for for specifying
partition columns. Hive also has this limitation and it wouldn't be too hard to support
in the future.
Change-Id: I4ca3c3b8f1576441b8bb5ed9dc521d7dfa96ab74
Reviewed-on: http://gerrit.ent.cloudera.com:8080/157
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: Lenni Kuff <lskuff@cloudera.com>
