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This change adds support for reading NDV statistics from Puffin files
when they are available for the current snapshot. Puffin files or blobs
that were written for other snapshots than the current one are ignored.
Because this behaviour is different from what we have for HMS stats and
may therefore be unintuitive for users, reading Puffin stats is disabled
by default; set the "--disable_reading_puffin_stats" startup flag to
false to enable it.
When Puffin stats reading is enabled, the NDV values read from Puffin
files take precedence over NDV values stored in the HMS. This is because
we only read Puffin stats for the current snapshot, so these values are
always up-to-date, while the values in the HMS may be stale.
Note that it is currently not possible to drop Puffin stats from Impala.
For this reason, this patch also introduces two ways of disabling the
reading of Puffin stats:
- globally, with the aforementioned "--disable_reading_puffin_stats"
startup flag: when it is set to true, Impala will never read Puffin
stats
- for specific tables, by setting the
"impala.iceberg_disable_reading_puffin_stats" table property to
true.
Note that this change is only about reading Puffin files, Impala does
not yet support writing them.
Testing:
- created the PuffinDataGenerator tool which can generate Puffin files
and metadata.json files for different scenarios (e.g. all stats are
in the same Puffin file; stats for different columns are in different
Puffin files; some Puffin files are corrupt etc.). The generated
files are under the "testdata/ice_puffin/generated" directory.
- The new custom cluster test class
'test_iceberg_with_puffin.py::TestIcebergTableWithPuffinStats' uses
the generated data to test various scenarios.
- Added custom cluster tests that test the
'disable_reading_puffin_stats' startup flag.
Change-Id: I50c1228988960a686d08a9b2942e01e366678866
Reviewed-on: http://gerrit.cloudera.org:8080/21605
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
This directory contains Impala test data sets. The directory layout is structured as follows:
datasets/
<data set>/<data set>_schema_template.sql
<data set>/<data files SF1>/data files
<data set>/<data files SF2>/data files
Where SF is the scale factor controlling data size. This allows for scaling the same schema to
different sizes based on the target test environment.
The schema template SQL files have the following format:
The goal is to provide a single place to define a table + data files
and have the schema and data load statements generated for each combination of file
format, compression, etc. The way this works is by specifying how to create a
'base table'. The base table can be used to generate tables in other file formats
by performing the defined INSERT / SELECT INTO statement. Each new table using the
file format/compression combination needs to have a unique name, so all the
statements are pameterized on table name.
The template file is read in by the 'generate_schema_statements.py' script to
to generate all the schema for the Impala benchmark tests.
Each table is defined as a new section in the file with the following format:
====
---- SECTION NAME
section contents
...
---- ANOTHER SECTION
... section contents
---- ... more sections...
Note that tables are delimited by '====' and that even the first table in the
file must include this header line.
The supported section names are:
DATASET
Data set name - Used to group sets of tables together
BASE_TABLE_NAME
The name of the table within the database
CREATE
Explicit CREATE statement used to create the table (executed by Impala)
CREATE_HIVE
Same as the above, but will be executed by Hive instead. If specified,
'CREATE' must not be specified.
CREATE_KUDU
Customized CREATE TABLE statement used to create the table for Kudu-specific
syntax.
COLUMNS
PARTITION_COLUMNS
ROW_FORMAT
HBASE_COLUMN_FAMILIES
TABLE_PROPERTIES
HBASE_REGION_SPLITS
If no explicit CREATE statement is provided, a CREATE statement is generated
from these sections (see 'build_table_template' function in
'generate-schema-statements.py' for details)
ALTER
A set of ALTER statements to be executed after the table is created
(typically to add partitions, but may also be used for other settings that
cannot be specified directly in the CREATE TABLE statement).
These statements are ignored for HBase and Kudu tables.
LOAD
The statement used to load the base (text) form of the table. This is
typically a LOAD DATA statement.
DEPENDENT_LOAD
DEPENDENT_LOAD_KUDU
DEPENDENT_LOAD_HIVE
DEPENDENT_LOAD_ACID
Statements to be executed during the "dependent load" phase. These statements
are run after the initial (base table) load is complete.
HIVE_MAJOR_VERSION
The required major version of Hive for this table. If the major version
of Hive at runtime does not exactly match the version specified in this section,
the table will be skipped.
NOTE: this is not a _minimum_ version -- if HIVE_MAJOR_VERSION specifies '2',
the table will _not_ be loaded/created on Hive 3.