Oracle command hangs when using view for "WHERE x IN..." subquery
- by Calvin Fisher
I'm working on a web service that fetches data from an oracle data source in chunks and passes it back to an indexing/search tool in XML format. I'm the C#/.NET guy, and am kind of fuzzy on parts of Oracle.
Our Oracle team gave us the following script to run, and it works well:
SELECT ROWID, [columns]
FROM [table]
WHERE ROWID IN (
SELECT ROWID
FROM (
SELECT ROWID
FROM [table]
WHERE ROWID > '[previous_batch_last_rowid]'
ORDER BY ROWID
)
WHERE ROWNUM <= 10000
)
ORDER BY ROWID
10,000 rows is an arbitrary but reasonable chunk size and ROWID is sufficiently unique for our purposes to use as a UID since each indexing run hits only one table at a time. Bracketed values are filled in programmatically by the web service.
Now we're going to start adding views to the indexing, each of which will union a few separate tables. Since ROWID would no longer function as a unique identifier, they added a column to the views (VIEW_UNIQUE_ID) that concatenates the ROWIDs from the component tables to construct a UID for each union.
But this script does not work, even though it follows the same form as the previous one:
SELECT VIEW_UNIQUE_ID, [columns]
FROM [view]
WHERE VIEW_UNIQUE_ID IN (
SELECT VIEW_UNIQUE_ID
FROM (
SELECT VIEW_UNIQUE_ID
FROM [view]
WHERE ROWID > '[previous_batch_last_view_unique_id]'
ORDER BY VIEW_UNIQUE_ID
)
WHERE ROWNUM <= 10000
)
ORDER BY VIEW_UNIQUE_ID
It hangs indefinitely with no response from the Oracle server. I've waited 20+ minutes and the SQLTools dialog box indicating a running query remains the same, with no progress or updates.
I've tested each subquery independently and each works fine and takes a very short amount of time (<= 1 second), so the view itself is sound. But as soon as the inner two SELECT queries are added with "WHERE VIEW_UNIQUE_ID IN...", it hangs.
Why doesn't this query work for views? In what important way are they not interchangeable here?
