With such statistics we could consider other planner improvements. Hope this will answer your query to some extent. Right now you can run COMPUTE STATS for Kudu tables to compute table/column stats, but it doesn't support stats for partitions/tablets. 1. 4. I tried DESCRIBE EXTENDED, but that yielded numRows=0 which is obviously not correct. Reworks handling of corrupt table stats as follows: The stats of a table or partition are reported as corrupt if the numRows < -1, or if numRows == 0 but the table size is positive. The second column shows the actual space consumed by those files in HDFS. Armed with this information, we can execute a query that will list all tables in a specific database along with the disk space (size) of each. Here are a few ways of listing all the tables that exist in a database together with the number of rows they contain. The file format used for an Impala table has significant performance consequences. To check that table statistics are available for a table, and see the details of those statistics, use the statement SHOW TABLE STATS table_name. 4: insert. Is there a Hive query to quickly find table size (i.e. Normally, Impala would optimize this automatically, but we saw that the statistics were missing for the tables being joined. 2. 3. 3: Drop. (Which is why I want to avoid COUNT(*).) The 'show table stats' command shows the lack of tablet statistics, though this isn't useful: INDEX_LENGTH is the length (or size) of the index file for the table (also in bytes). Impala performs some optimizations using this metadata on its own, and other optimizations by using a combination of table and column statistics. Impala After Table Statement. There are much more to know about Impala Alter Table Statement.Like Altering the name of a table, Adding columns to a table, Dropping columns from a table, Changing the name and type of a column or Altering a Table using Hue. See SHOW Statement for details. number of rows) without launching a time-consuming MapReduce job? Some file formats include compression support that affects the size of data on the disk and, consequently, the amount of I/O and CPU resources required to deserialize data. DATA_LENGTH is the length (or size) of all data in the table (in bytes). IMPALA; IMPALA-1310; hdfs-parquet-table-writer.cc:818] Check failed: file_size_limit_ > DATA_PAGE_SIZE * columns_.size() (6291456 vs. 131072000) Basically, to change the structure or properties of an existing Impala table we use Impala Alter Table Statement. This is quite straightforward for a single table, but quickly gets tedious if there are a lot of tables, and also can be slow. There a few ways we could fix this: Add the missing statistics as described earlier. To get the number of rows in a single table we usually use SELECT COUNT(*) or SELECT COUNT_BIG(*). The drop command is used to remove a construct from Impala, where a construct can be a table, a view, or a database function. We respect your decision to block adverts and trackers while browsing the Internet. Now you need to flush the info , to update the dba_tab_modification table. The describe command has desc as a short cut. 2. Check dba_tab_modification: SQL[SYS@TCRMDB01]SQL>>]select INSERTS,UPDATES,DELETES,TRUNCATED,TIMESTAMP from dba_tab_modifications where TABLE_NAME='TEST' and TABLE_OWNER='SCOTT'; no rows selected As you can see, the dba_tab_modification is not showing any rows. Impala prefers having the table with the larger size on the right hand side of the graph, but in this case the reverse is true. The first column shows the actual size (raw size) of the files that users have placed in the various HDFS directories. The describe command of Impala gives the metadata of a table. Removes the Preconditions check reported in IMPALA-1657 in favor or issuing a corrupt table stats warning. It contains the information like columns and their data types.
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