MPP 数据分析平台，这些功 能都是必不可少的。 2) Mysql 查询优化器对于子查询、复制查询如多表关联、外关联的支 持等较弱，特别是在关联时对于三大 join 技术：hash join、merge join、nestloop join 的支持方面，Mysql 只支持最后一种 nestloop join（据说未来会支持 hash join），而多个大表关联分析时 hash join 是 这种是 Merge 关联，会将关联的两张表先按照关联字段做排序，通常 在内存不吃紧的情况下，排序算法不如 Hash 算法快。 这种是 Nested Loop 关联，等于是两张表做了笛卡尔积复杂度的匹配。 Big Date2.indd 45 16-11-22 下午3:38 46 我们来看一下，在内存资源充足的情况下，三种场景的复杂度： Hash Join：o(N) Merge Join：o(N×logN) Join 方法 不如我们期望，要找找原因，比如数据量评估错误，关联条件不对等。 通常，smallint、int、bigint 之间的关联是不能走等值关联的，也就是说， Hash Join 和 Merge Join 都是无法选择的，只能选择 Nestloop Join， 这很致命。因此，如果你不能确保所有相关联的字段具有相同的数据 类型，这三种数据类型中，建议永远不要使用 smallint 和 bigint，分别

and/or mirror segment was a symbolic link. Data Flow 32776 gpload, when invoked in update or merge mode, returned an error when it created its staging table with the same distribution key as the target gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the

and/or mirror segment was a symbolic link. Data Flow 32776 gpload, when invoked in update or merge mode, returned an error when it created its staging table with the same distribution key as the target gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 VMware Greenplum generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the

Data Loading N/A : Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 : Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the plan plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

Data Loading N/A : Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 : Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the plan plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the the plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the the plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the the plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

gpcheckcat. Data Loading N/A Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 VMware Tanzu generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the the plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned

Data Loading N/A : Reverts a previously-committed gpload improvement that removed a left-join merge because it introduced a performance regression in certain situations. 31613, 12454 : Resolves an generated an incorrect plan for some queries that included a merge join and dynamic partition elimination. The storage needed for the merge join key was incorrectly allocated on the inner side of the plan plan tree. This led to a SIGSEGV when executing the sort node of the inner side of the merge join. The problem was resolved by ensuring that only the nodes that need to use the join key are provisioned