Quanlong Huang created IMPALA-9805:
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Summary: Alter table recover partitions will repeatedly drop and
load partitions with inconsistent partition name strings between Impala and Hive
Key: IMPALA-9805
URL: https://issues.apache.org/jira/browse/IMPALA-9805
Project: IMPALA
Issue Type: Bug
Components: Catalog
Reporter: Quanlong Huang
Assignee: Quanlong Huang
For AlterTable Recover Partitions, Impala compares the Hive partition names
with the names of cached partitions to drop non-existing partitions and add new
partitions. However, comparing by name strings is not enough since some
partitions will have inconsistent names between Hive and Impala. This usually
happens when the partition directory is created by non-Hive apps.
Let's say external table my_part_tbl is partitioned by (year int, month
{color:#de350b}*int*{color}, day {color:#de350b}*int*{color}). User creates and
uploads data to HDFS dir
year=2020/month={color:#ff0000}*01*{color}/day={color:#ff0000}*01*{color}{color:#172b4d},
and then triggers an AlterTable RecoverPartitions command in Impala. Impala
will create partition
(year=2020/month=*1*{color}/day={color:#de350b}*1*{color}) in Hive using this
location
".../year=2020/month=*{color:#de350b}01{color}*/day=*{color:#de350b}01{color}*".
Next time when running AlterTable RecoverPartition again (e.g. when new
partition dirs are created again), the partition name list got from Hive is
[year=2020/month=01/day=01]. However, the name list of cached partitions is
[year=2020/month=1/day=1]. Impala will drop this partition and load it as a new
partition.
{color:#172b4d}This impacts the performance of AlterTable RecoverPartition on
partitioned tables if the partition directories are all in such case. Many
partitions will be reload and reload.{color}
*{color:#172b4d}Reproduction{color}*
{code:java}
impala> create external table my_part_tbl (id int) partitioned by (year int,
month int, day int);
impala> describe formatted my_part_tbl;{code}
Found the table location is hdfs://localhost:20500/test-warehouse/my_part_tbl
Create and upload data to a partition dir using HDFS CLI:
{code:java}
$ cat data.txt
1
2
3
$ hdfs dfs -mkdir -p
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=01/day=01
$ hdfs dfs -mkdir -p
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=01/day=02
$ hdfs dfs -mkdir -p
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=09/day=01
$ hdfs dfs -mkdir -p
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=09/day=02
$ hdfs dfs -put data.txt
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=01/day=01
$ hdfs dfs -put data.txt
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=01/day=02
$ hdfs dfs -put data.txt
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=09/day=01
$ hdfs dfs -put data.txt
hdfs://localhost:20500/test-warehouse/my_part_tbl/year=2020/month=09/day=02{code}
Let Impala detect these partitions.
{code:java}
impala> alter table my_part_tbl recover partitions;
{code}
Then everytime when running AlterTable RecoverPartitions, these 4 partitions
will be reloaded again. The logs of catalogd reflects this:
{code:java}
I0531 11:51:45.037181 27878 HdfsTable.java:1001] Reloading metadata for all
partition(s) of default.my_part_tbl (ALTER TABLE RECOVER_PARTITIONS)
I0531 11:51:45.037286 27878 HdfsTable.java:2095] Load Valid Write Id List Done.
Time taken: 4.456us
I0531 11:51:45.049304 27878 ParallelFileMetadataLoader.java:144] Loading file
and block metadata for 4 paths for table default.my_part_tbl using a thread
pool of size 4
I0531 11:51:45.053562 27878 HdfsTable.java:697] Loaded file and block metadata
for default.my_part_tbl partitions: year=2020/month=1/day=1,
year=2020/month=1/day=2, year=2020/month=9/day=1, and 1 others. Time taken:
4.537ms
I0531 11:51:45.053689 27878 HdfsTable.java:1032] Incrementally loaded table
metadata for: default.my_part_tbl
I0531 11:51:45.279531 26899 catalog-server.cc:735] Collected update:
1:TABLE:default.my_part_tbl, version=1512, original size=3989, compressed
size=1294
I0531 11:51:45.281633 26899 catalog-server.cc:735] Collected update:
1:CATALOG_SERVICE_ID, version=1512, original size=60, compressed size=58
I0531 11:51:47.277819 26906 catalog-server.cc:340] A catalog update with 2
entries is assembled. Catalog version: 1512 Last sent catalog version: 1511
{code}
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