cloud-fan opened a new pull request #25747: [SPARK-29039][SQL] centralize the catalog and table lookup logic URL: https://github.com/apache/spark/pull/25747 <!-- Thanks for sending a pull request! Here are some tips for you: 1. If this is your first time, please read our contributor guidelines: https://spark.apache.org/contributing.html 2. Ensure you have added or run the appropriate tests for your PR: https://spark.apache.org/developer-tools.html 3. If the PR is unfinished, add '[WIP]' in your PR title, e.g., '[WIP][SPARK-XXXX] Your PR title ...'. 4. Be sure to keep the PR description updated to reflect all changes. 5. Please write your PR title to summarize what this PR proposes. 6. If possible, provide a concise example to reproduce the issue for a faster review. --> ### What changes were proposed in this pull request? <!-- Please clarify what changes you are proposing. The purpose of this section is to outline the changes and how this PR fixes the issue. If possible, please consider writing useful notes for better and faster reviews in your PR. See the examples below. 1. If you refactor some codes with changing classes, showing the class hierarchy will help reviewers. 2. If you fix some SQL features, you can provide some references of other DBMSes. 3. If there is design documentation, please add the link. 4. If there is a discussion in the mailing list, please add the link. --> Currently we deal with different `ParsedStatement` in many places and write duplicated catalog/table lookup logic. In general the lookup logic is 1. try look up the catalog by name. If no such catalog, and default catalog is not set, convert `ParsedStatement` to v1 command like `ShowDatabasesCommand`. Otherwise, convert `ParsedStatement` to v2 command like `ShowNamespaces`. 2. try look up the table by name. If no such table, fail. If the table is a `V1Table`, convert `ParsedStatement` to v1 command like `CreateTable`. Otherwise, convert `ParsedStatement` to v2 command like `CreateV2Table`. However, since the code is duplicated we don't apply this lookup logic consistently. For example, we forget to consider the v2 session catalog in several places. This PR introduces a new framework for catalog/table lookup, to centralize the logic in one places. We categorize the `ParsedStatement` into 3 kinds: 1. `StatementRequiringCatalog`. It carries an n-part name and needs to look up the catalog to resolve itself. If the returned catalog is v2 session catalog, leave the plan unchanged and wait for other rules to resolve it (e.g. convert it to v1 command) 2. `StatementRequiringCatalogAndTable`. It carries an n-part name and needs to look up the catalog and table to resolve itself. If the returned table is `V1Table`, leave the plan unchanged and wait for other rules to resolve it (e.g. convert it to v1 command) 3. general `ParsedStatement`. It carries `UnresolvedRelation` which will be resolved to temp view, view or tables. ### Why are the changes needed? <!-- Please clarify why the changes are needed. For instance, 1. If you propose a new API, clarify the use case for a new API. 2. If you fix a bug, you can clarify why it is a bug. --> Reduce duplicated code and make the catalog/table lookup logic consistent. ### Does this PR introduce any user-facing change? <!-- If yes, please clarify the previous behavior and the change this PR proposes - provide the console output, description and/or an example to show the behavior difference if possible. If no, write 'No'. --> no ### How was this patch tested? <!-- If tests were added, say they were added here. Please make sure to add some test cases that check the changes thoroughly including negative and positive cases if possible. If it was tested in a way different from regular unit tests, please clarify how you tested step by step, ideally copy and paste-able, so that other reviewers can test and check, and descendants can verify in the future. If tests were not added, please describe why they were not added and/or why it was difficult to add. --> existing tests
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