sql: make view descriptors depend on table/columns by IDs #17501
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If a view is defined by a query over table `d.t`, and this view's query is inspected (using either SHOW CREATE VIEW or pg_catalog) in the context of database `d`, ensure that the prefix `d.` is hidden. This is useful to ease reuse of the view definition when migrating databases.
This hidden bug cropped up while investigating different ways to encode view descriptors.
This patch makes it possible to use the numeric table reference syntax with a selection of columns (e.g. `[123(1,2,3)]`) when the reference is for a view. This selects a subset of the view's definition.
… the query Prior to this patch, a view defined with `CREATE VIEW v(x) FROM SELECT y FROM ...` would only store the name "x" in the descriptor. This would cause queries to pg_catalog or information_schema to hide the fact the view renders a column named "x" (only showing "SELECT y ..."). This patch improves upon this situation by forcing an explicit rename in the view query if the view definition changes the names. This was the most glaring limitation of the previous approach, but in addition to this a bug was lurking: a view created with `CREATE VIEW v(rowid) FROM TABLE t`, which *intends* to reveal the `rowid` such that subsequently `SELECT * FROM v` actually selects `rowid`, didn't work as intended: when the view plan was expanded, the `rowid` column would be picked from the underlying plan, which would make it hidden, which would subsequently cause `SELECT * FROM v` to not pick any column at all. The explicit rename approach taken in this patch fixes this bug. This bug probably never affected anyone given how unlikely the use case is, however fixing this fits the general effort of view descriptor improvements this patch is part of.
For example: ``` > CREATE TABLE t.kv(k INT PRIMARY KEY, v INT); > CREATE VIEW vx AS SELECT v AS x FROM t.kv; > SHOW CREATE VIEW t.vx; +------+-----------------------------------------------+ | View | CreateView | +------+-----------------------------------------------+ | vx | -- t.kv(k,v) = [71(1,2)] | | | CREATE VIEW vx (x) AS SELECT v AS x FROM t.kv | +------+-----------------------------------------------+ (1 row) ``` i.e. the view query is unchanged but the view descriptor tracks the mapping of names into the query to the actual IDs of the dependencies. This information is reported in SHOW CREATE VIEW as a SQL comment and in more details in `crdb_internal.backward_dependencies`. When the view query is loaded, this information in the view descriptor overrides the regular name resolution path.
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This change is |
This was referenced Aug 8, 2017
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Reminder: checks that this fixes #12611 |
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Is this abandoned / should we close it? |
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It's not abandoned and the idea in here is still sound. |
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<3 we should still do this |
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It's not being entirely superseded. The truncate PR (#52235) would allow us to do this without having to worry about remapping IDs on truncate. |
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I'm assigning this PR to the relevant SQL projects so that folk who intend to work on this can pluck utility out of it when the work is restarted. |
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@mgartner @postamar @chengxiong-ruan do you want to take a last look at this to see if there's anything worth salvaging, even if just ideas? Then I can close this and let it sleep in history forever. |
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Supersedes #15388.
Contains prefix commits from #17475; will rebase when that merges.
This patch makes one more step towards addressing #10028/#10083.
For example:
i.e. the view query is unchanged but the view descriptor tracks the
mapping of names into the query to the actual IDs of the
dependencies. This information is reported in SHOW CREATE VIEW as a
SQL comment and in more details in
crdb_internal.backward_dependencies.When the view query is loaded, this information in the view descriptor
overrides the regular name resolution path. For this we introduce a new
"lookupEnvironment" which allows view descriptors to override the name
to ID mapping for relation names, column names and index names.