Add pre_execution_queries parameter to run setup queries before main query on Postgres and MySQL source #729
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…query on Postgres and MySQL source
…o feature/pre-execution-queries
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Hi @wangxiaoying, I have fixed the tests and applied formatting. Apologies for missing them earlier. Could you please rerun the workflow? |
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Thank you @jsjasonseba for the PR! I will take a deeper look at it by this weekend. |
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Thank you @jsjasonseba for the PR, I think it looks good in general!
I left a few comments in the review. Please let me know if you have any questions!
| @@ -107,6 +107,8 @@ where | |||
| self.origin_query = query; | |||
| } | |||
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| fn set_pre_execution_queries(&mut self, _pre_execution_queries: Option<&[String]>) {} | |||
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mark with unimplemented for unsupported sources?
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Wow that's neat, just learned about this. Will implement them soon.
| let mut conn = self.pool.get()?; | ||
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| if let Some(queries) = &self.pre_execution_queries { | ||
| for query in queries { |
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rename the inner query (e.g., to pre_query) so that it won't be confused with the outer query variable?
| dst: &'w mut D, | ||
| queries: &[Q], | ||
| origin_query: Option<String>, | ||
| pre_execution_queries: Option<&[String]>, |
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Instead of adding a new parameter to the constructor, maybe it is better to add a set_pre_execution_queries function? When using the dispatcher, we can:
- let dispatcher = Dispatcher::new(...); -- remain the same
- dispatcher.set_pre_execution_queries(...); --- optional, only set when needed
- dispatcher.run() -- remain the same
I think it could be a way to avoid the breaking change. What do you think?
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Yeah, I think this a better approach. Thanks for the suggestion.
| @@ -1238,4 +1238,33 @@ def test_postgres_partition_with_orderby_limit_desc(postgres_url: str) -> None: | |||
| }, | |||
| ) | |||
| df.sort_values(by="test_int", inplace=True, ignore_index=True) | |||
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We probably also need to add a test for applying pre_execution_queries with partitioning enabled. To make the test case easier, we can use query = [list of partitioned query] to directly specify the query for each partition. For example:
query = [
"SELECT CAST(name AS TEXT) AS name, CAST(setting AS INTEGER) FROM pg_settings WHERE name = 'statement_timeout'",
"SELECT CAST(name AS TEXT) AS name, CAST(setting AS INTEGER) FROM pg_settings WHERE name = 'idle_in_transaction_session_timeout'"
]
pre_execution_query = pre_execution_query = [
"SET SESSION statement_timeout = 2151",
"SET SESSION idle_in_transaction_session_timeout = 2252",
]
df = read_sql(postgres_url, query, pre_execution_query=pre_execution_query)
expected = pd.DataFrame(
index=range(2),
data={
"name": pd.Series(["statement_timeout", "idle_in_transaction_session_timeout"], dtype="str"),
"setting": pd.Series([2151, 2252], dtype="Int64"),
},
)
This PR attempts to solve: #728
Also related issues: #645 #471 #656 #512
This PR adds pre_execution_queries parameter to run setup queries before main query. SET statements are typically applied on session/connection scope, so the pre-execution queries must be applied to each connection on each partition. This is implemented by running the pre-execution queries using a connection before assigning the connection to SourcePartition. This will allow all queries run by each connection on each partition to have the necessary settings.
Currently implemented in Postgres and MySQL sources.
I am quite new with rust and I noticed this change is quite breaking to the rust API since rust does not support default args. Please let me know if there is a better way to do this.