user, issue another INVALIDATE METADATA to make Impala aware of the change. compute_stats_params. Johnd832 says: May 19, 2016 at 4:13 am. In the documentation of the Denodo Platform you will find all the information you need to build Data Virtualization solutions. New Features in Impala 1.2.4 for details. Metadata of existing tables changes. For the full list of issues closed in this release, including bug fixes, see the changelog for Impala 3.2.. But when I deploy the package, I get an error: Custom metadata type Marketing_Cloud_Config__mdt is not available in this organization. One CatalogOpExecutor is typically created per catalog // operation. Does it mean in the above case, that both are goi In particular, issue a REFRESH for a table after adding or removing files Design and Use Context to Find ITSM Answers by Adam Rauh May 15, 2018 “Data is content, and metadata is context. The following is a list of noteworthy issues fixed in Impala 3.2: . Develop an Asset Compute metadata worker. ImpalaClient.truncate_table (table_name[, ... ImpalaTable.compute_stats ([incremental]) Invoke Impala COMPUTE STATS command to compute column, table, and partition statistics. Stats have been computed, but the row count reverts back to -1 after an INVALIDATE METADATA. METADATA waits to reload the metadata when needed for a subsequent query, but reloads all the Much of the metadata for Kudu tables is handled by the underlying 2. REFRESH reloads the metadata immediately, but only loads the block location My package contains custom Metadata to be deployed.I have made sure that they are in my package and also in package.xml. If you are not familiar This is the default. 2. each time doing `compute stats` got the fields doubled: compute table stats t2; desc t2; Query: describe t2-----name : type : comment -----id : int : cid : int : id : int : cid : int -----the workaround is to invalidate the metadata: invalidate metadata t2; this is kudu 0.8.0 on cdh5.7. In Impala 1.2.4 and higher, you can specify a table name with INVALIDATE METADATA after Attachments. Note that during prewarm (which can take a long time if the metadata size is large), we will allow the metastore to server requests. Issue INVALIDATE METADATA command, optionally only applying to a particular table. for tables where the data resides in the Amazon Simple Storage Service (S3). When the value of this argument is TRUE, deletes statistics of tables in a database even if they are locked 4. by Kudu, and Impala does not cache any block locality metadata Neither statement is needed when data is If you specify a table name, only the metadata for that one table is flushed. Once the table is known by Impala, you can issue REFRESH HDFS-backed tables. impala-shell. Content: Data Vs Metadata. New tables are added, and Impala will use the tables. The ability to specify INVALIDATE METADATA but subsequent statements such as SELECT Though there are not many differences between data and metadata, but in this article I have discussed the basic ones in the comparison chart shown below. for all tables and databases. Before the Impala node is already aware of, when you create a new table in the Hive shell, enter example the impala user does not have permission to write to the data directory for the 5. In other words, every session has a shared lock on the database which is running. where you ran ALTER TABLE, INSERT, or other table-modifying statement. A new partition with new data is loaded into a table via Hive. data for newly added data files, making it a less expensive operation overall. How to import compressed AVRO files to Impala table? A new partition with new data is loaded into a table via Hive database, and require less metadata caching on the Impala side. partitions. Metadata Operation’s •Invalidate Metadata • Runs async to discard the loaded metadata catalog cache, metadata load will be triggered by any subsequent queries. Overview of Impala Metadata and the Metastore for background information. The scheduler then endeavors to match user requests for instances of the given flavor to a host aggregate with the same key-value pair in its metadata. stats list counters ext_cache_obj Counters for object name: ext_cache_obj type blocks size usage accesses disk_reads_replaced hit hit_normal_lev0 hit_metadata_file hit_directory hit_indirect total_metadata_hits miss miss_metadata_file miss_directory miss_indirect Now, newly created or altered objects are typically the impala user, must have execute permissions for all the relevant directories holding table data. Required after a table is created through the Hive shell, COMPUTE INCREMENTAL STATS; COMPUTE STATS; CREATE ROLE; CREATE TABLE. You must be connected to an Impala daemon to be able to run these -- which trigger a refresh of the Impala-specific metadata cache (in your case you probably just need a REFRESH of the list of files in each partition, not a wholesale INVALIDATE to rebuild the list of all partitions and all their files from scratch) The Impala Catalog Service for more information on the catalog service. In this blog post series, we are going to show how the charts and metrics on Cloudera Manager (CM) […] See The principle isn’t to artificially turn out to be effective, ffedfbegaege. For more examples of using REFRESH and INVALIDATE METADATA with a If you use Impala version 1.0, the INVALIDATE METADATA statement works just like the Impala 1.0 REFRESH statement did. 2. each time doing `compute stats` got the fields doubled: compute table stats t2; desc t2; Query: describe t2-----name : type : comment -----id : int : cid : int : id : int : cid : int -----the workaround is to invalidate the metadata: invalidate metadata t2; this is kudu 0.8.0 on cdh5.7. that all metadata updates require an Impala update. and the new database are visible to Impala. Computing stats for groups of partitions: In Impala 2.8 and higher, you can run COMPUTE INCREMENTAL STATS on multiple partitions, instead of the entire table or one partition at a time. The SERVER or DATABASE level Sentry privileges are changed. This is a relatively expensive operation compared to the incremental metadata update done by the While this is arguably a Hive bug, I'd recommend that Impala should just unconditionally update the stats when running a COMPUTE STATS. However, this does not mean If you run "compute incremental stats" in Impala again. gcloud . if ... // as INVALIDATE METADATA. 6. Also Compute stats is a costly operations hence should be used very cautiosly . One design choice yet to make is whether we need to cache aggregated stats, or calculate them on the fly in the CachedStore assuming all column stats are in memory. By default, the cached metadata for all tables is flushed. Hi Franck, Thanks for the heads up on the broken link. Use DBMS_STATS.AUTO_INVALIDATE. @@ -186,6 +186,9 @@ struct TQueryCtx {// Set if this is a child query (e.g. 1. Database and table metadata is typically modified by: INVALIDATE METADATA causes the metadata for that table to be marked as stale, and reloaded the INVALIDATE METADATA statement works just like the Impala 1.0 REFRESH in the associated S3 data directory. A compute [incremental] stats appears to not set the row count. for Kudu tables. Impala 1.2.4 also includes other changes to make the metadata broadcast Example scenario where this bug may happen: 1. How can I run Hive Explain command from java code? before accessing the new database or table from the other node. for example if the next reference to the table is during a benchmark test. Back to the previous screen capture, we can see that on the first row the UPDATE STATISTICS query is holding a shared database lock which is pretty obvious because the UPDATE STATISTICS query is running in the context of our test database. INVALIDATE METADATA : Use INVALIDATE METADATAif data was altered in a more extensive way, s uch as being reorganized by the HDFS balancer, to avoid performance issues like defeated short-circuit local reads. or SHOW TABLE STATS could fail. METADATA to avoid a performance penalty from reduced local reads. When executing the corresponding alterPartition() RPC in the Hive Metastore, the row count will be reset because the STATS_GENERATED_VIA_STATS_TASK parameter was not set. The default can be changed using the SET_PARAM Procedure. that represents an oversight. INVALIDATE METADATA statement was issued, Impala would give a "table not found" error The first time you do COMPUTE INCREMENTAL STATS it will compute the incremental stats for all partitions. The DESCRIBE statements cause the latest In Impala 1.2 and higher, a dedicated daemon (catalogd) broadcasts DDL changes made Compute nodes … files and directories, caching this information so that a statement can be cancelled immediately if for 2. Impressive brief and clear explaination and demo by examples, well done indeed. The row count reverts back to -1 because the stats have not been persisted, Explanation for This Bug Even for a single table, INVALIDATE METADATA is more expensive through Impala to all Impala nodes. the use cases of the Impala 1.0 REFRESH statement. INVALIDATE METADATA and REFRESH are counterparts: INVALIDATE • Should be run when ... • Compute Stats is very CPU-intensive –Based on number of rows, number of data files, the Custom Asset Compute workers can produce XMP (XML) data that is sent back to AEM and stored as metadata on an asset. INVALIDATE METADATA is required when the following changes are made outside of Impala, in Hive and other Hive client, such as SparkSQL: . earlier releases, that statement would have returned an error indicating an unknown table, requiring you to are made directly to Kudu through a client program using the Kudu API. INVALIDATE METADATA and REFRESH are counterparts: . Administrators do this by setting metadata on a host aggregate, and matching flavor extra specifications. INVALIDATE METADATA table_name If data was altered in some against a table whose metadata is invalidated, Impala reloads the associated metadata before the query clients query directly. This example illustrates creating a new database and new table in Hive, then doing an INVALIDATE INVALIDATE METADATA is run on the table in Impala after creating it. Therefore, if some other entity modifies information used by Impala in the metastore with Impala's metadata caching where issues in stats persistence will only be observable after an INVALIDATE METADATA. statement did, while the Impala 1.1 REFRESH is optimized for the common use case of adding or in unexpected paths, if it uses partitioning or force. Occurence of DROP STATS followed by COMPUTE INCREMENTAL STATS on one or more table; Occurence of INVALIDATE METADATA on tables followed by immediate SELECT or REFRESH on same tables; Actions: INVALIDATE METADATA usage should be limited. When already in the broken "-1" state, re-computing the stats for the affected partition fixes the problem. COMPUTE INCREMENTAL STATS; COMPUTE STATS; CREATE ROLE; CREATE TABLE. The user ID that the impalad daemon runs under, new data files to an existing table, thus the table name argument is now required. Issues with permissions might not cause an immediate error for this statement, Making the behavior dependent on the existing metadata state is brittle and hard to reason about and debug, esp. Check out the following list of counters. you will get the same RowCount, so the following check will not be satisfied and StatsSetupConst.STATS_GENERATED_VIA_STATS_TASK will not be set in Impala's CatalogOpExecutor.java. prefer REFRESH rather than INVALIDATE METADATA. For example, information about partitions in Kudu tables is managed Do I need to first deploy custom metadata and then deploy the rest? By default, the cached metadata for all tables is flushed. Use the STORED AS PARQUET or STORED AS TEXTFILE clause with CREATE TABLE to identify the format of the underlying data files. See Impala reports any lack of write permissions as an INFO message in the log file, in case Stats on the new partition are computed in Impala with COMPUTE INCREMENTAL STATS Important: After adding or replacing data in a table used in performance-critical queries, issue a COMPUTE STATS statement to make sure all statistics are up-to-date. ... Issue an INVALIDATE METADATA statement manually on the other nodes to update metadata. ; IMPALA-941- Impala supports fully qualified table names that start with a number. REFRESH Statement, Overview of Impala Metadata and the Metastore, Switching Back and Forth Between Impala and Hive, Using Impala with the Amazon S3 Filesystem. Impala node, you needed to issue an INVALIDATE METADATA statement on another Impala node (This checking does not apply when the catalogd configuration option // The existing row count value wasn't set or has changed. Snipped from Hive's MetaStoreUtils.hava: So if partition stats already exists but not computed by impala, compute incremental stats will cause stats been reset back to -1. Query project metadata: gcloud compute project-info describe \ --flatten="commonInstanceMetadata[]" Query instance metadata: gcloud compute instances describe example-instance \ --flatten="metadata[]" Use the --flatten flag to scope the output to a relevant metadata key. See Using Impala with the Amazon S3 Filesystem for details about working with S3 tables. If a table has already been cached, the requests for that table (and its partitions and statistics) can be served from the cache. Given the complexity of the system and all the moving parts, troubleshooting can be time-consuming and overwhelming. 1. When using COMPUTE STATS command on any table in my environment i am getting: [impala-node] > compute stats table1; Query: ... Cloudera Impala INVALIDATE METADATA. table_name after you add data files for that table. statements are needed less frequently for Kudu tables than for Query project metadata: gcloud compute project-info describe \ --flatten="commonInstanceMetadata[]" Query instance metadata: gcloud compute instances describe example-instance \ --flatten="metadata[]" Use the --flatten flag to scope the output to a relevant metadata key. Here is why the stats is reset to -1. Note that in Hive versions after CDH 5.3 this bug does not happen anymore because the updatePartitionStatsFast() function is not called in the Hive Metastore in the above workflow anymore. Use the STORED AS PARQUET or STORED AS TEXTFILE clause with CREATE TABLE to identify the format of the underlying data files. At this point, SHOW TABLE STATS shows the correct row count If you specify a table name, only the metadata for A metadata update for an impalad instance is required if: A metadata update for an Impala node is not required when you issue queries from the same Impala node The following example shows how you might use the INVALIDATE METADATA statement after ImpalaTable.describe_formatted DBMS_STATS.DELETE_COLUMN_STATS ( ownname VARCHAR2, tabname VARCHAR2, colname VARCHAR2, partname VARCHAR2 DEFAULT NULL, stattab VARCHAR2 DEFAULT NULL, statid VARCHAR2 DEFAULT NULL, cascade_parts BOOLEAN DEFAULT TRUE, statown VARCHAR2 DEFAULT NULL, no_invalidate BOOLEAN DEFAULT to_no_invalidate_type ( get_param('NO_INVALIDATE')), force BOOLEAN DEFAULT FALSE, col_stat… Even for a single table, INVALIDATE METADATA is more expensive than REFRESH, so prefer REFRESH in the common case where you add new data files for an existing table. Use the TBLPROPERTIES clause with CREATE TABLE to associate random metadata with a table as key-value pairs. If you use Impala version 1.0, the INVALIDATE METADATA statement works just like the Impala 1.0 REFRESH statement did. For a huge table, that process could take a noticeable amount of time; For a user-facing system like Apache Impala, bad performance and downtime can have serious negative impacts on your business. 1. So here is another post I keep mainly for my own reference, since I regularly need to gather new schema statistics.The information here is based on the Oracle documentation for DBMS_STATS, where all the information is available.. Compute incremental stats is most suitable for scenarios where data typically changes in a few partitions only, e.g., adding partitions or appending to the latest partition, etc. than REFRESH, so prefer REFRESH in the common case where you add new data Metadata can be much more revealing than data, especially when collected in the aggregate.” —Bruce Schneier, Data and Goliath. REFRESH statement, so in the common scenario of adding new data files to an existing table, Regarding your question on the FOR COLUMNS syntax, you are correct the initial SIZE parameter (immediately after the FOR COLUMNS) is the default size picked up for all of the columns listed after that, unless there is a specific SIZE parameter specified immediately after one of the columns. IMPALA-341 - Remote profiles are no longer ignored by the coordinator for the queries with the LIMIT clause. added to, removed, or updated in a Kudu table, even if the changes If you used Impala version 1.0, more extensive way, such as being reorganized by the HDFS balancer, use INVALIDATE with the way Impala uses metadata and how it shares the same metastore database as Hive, see INVALIDATE METADATA new_table before you can see the new table in Under Custom metadata, view the instance's custom metadata. requires a table name parameter, to flush the metadata for all tables at once, use the INVALIDATE Disable stats autogathering in Hive when loading the data, 2. class CatalogOpExecutor existing_part_stats, &update_stats_params); // col_stats_schema and col_stats_data will be empty if there was no column stats query. Because REFRESH table_name only works for tables that the current But in either case, once we turn on aggregate stats in CacheStore, we shall turn off it in ObjectStore (already have a switch) so we don’t do it … REFRESH and INVALIDATE METADATA commands are specific to Impala. In table. storage layer. Example scenario where this bug may happen: Impala. Workarounds collection of stats netapp now provides. 3. gcloud . Rows two through six tell us that we have locks on the table metadata. table_name for a table created in Hive is a new capability in Impala 1.2.4. the table is created in Hive, allowing you to make individual tables visible to Impala without doing a full You include comparison operators other than = in the PARTITION clause, and the COMPUTE INCREMENTAL STATS statement applies to all partitions that match the comparison expression. --load_catalog_in_background is set to false, which it is by default.) The next time the current Impala node performs a query proceeds. By default, the INVALIDATE METADATA command checks HDFS permissions of the underlying data Manually alter the numRows to -1 before doing COMPUTE [INCREMENTAL] STATS in Impala, 3. After that operation, the catalog and all the Impala coordinators only know about the existence of databases and tables and nothing more. Hence chose Refresh command vs Compute stats accordingly . Library for exploring and validating machine learning data - tensorflow/data-validation You must still use the INVALIDATE METADATA that one table is flushed. METADATA statement in Impala using the fully qualified table name, after which both the new table Consider updating statistics for a table after any INSERT, LOAD DATA, or CREATE TABLE AS SELECT statement in Impala, or after loading data through Hive and doing a REFRESH table_name in Impala. Run REFRESH table_name or picked up automatically by all Impala nodes. Data vs. Metadata. (A table could have data spread across multiple directories, Attachments. The REFRESH and INVALIDATE METADATA statements also cache metadata METADATA statement. Marks the metadata for one or all tables as stale. the next time the table is referenced. The COMPUTE INCREMENTAL STATS variation is a shortcut for partitioned tables that works on a subset of partitions rather than the entire table. thus you might prefer to use REFRESH where practical, to avoid an unpredictable delay later, Proposed Solution creating new tables (such as SequenceFile or HBase tables) through the Hive shell. before the table is available for Impala queries. to have Oracle decide when to invalidate dependent cursors. Attaching the screenshots. Hive has hive.stats.autogather=true files for an existing table. Scenario 4 Rebuilding Indexes vs. Updating Statistics […] Mark says: May 17, 2016 at 5:50 am. metadata to be immediately loaded for the tables, avoiding a delay the next time those tables are queried. Metadata specifies the relevant information about the data which helps in identifying the nature and feature of the data. It should be working fine now. a child of a COMPUTE STATS request) 9: optional Types.TUniqueId parent_query_id // List of tables suspected to have corrupt stats 10: optional list tables_with_corrupt_stats // Context of a fragment instance, including its unique id, the total number combination of Impala and Hive operations, see Switching Back and Forth Between Impala and Hive. reload of the catalog metadata. INVALIDATE METADATA is an asynchronous operations that simply discards the loaded metadata from the catalog and coordinator caches. Common use cases include: Integrations with 3rd party systems, such as a PIM (Product Information Management system), where additional metadata must be retrieved and stored on the asset