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Misleading error for incompletely created tables #38

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merged 5 commits into from Jan 9, 2015
Merged

Misleading error for incompletely created tables #38

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07acc17
Misleading error for incompletely created tables
onderkalaci Jan 5, 2015
6e690cb
Add unit test for distributed tables
onderkalaci Jan 5, 2015
6678cee
Update misleading error messages for incompletely created tables
onderkalaci Jan 8, 2015
ed8f95c
Merge remote-tracking branch 'origin/develop' into feature-issue#9
onderkalaci Jan 8, 2015
acef92f
Final style changes
onderkalaci Jan 9, 2015
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5 changes: 5 additions & 0 deletions expected/queries.out
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Expand Up @@ -13,6 +13,11 @@ SELECT master_create_distributed_table('articles', 'author_id');

(1 row)

-- test when a table is distributed but no shards created yet
SELECT count(*) from articles;
ERROR: cannot plan SELECT query
DETAIL: There are no existing shards for the distributed table.
HINT: Run "master_create_worker_shards" to create shards for the distributed table.
\set VERBOSITY terse
SELECT master_create_worker_shards('articles', 2, 1);
WARNING: Connection failed to adeadhost:5432
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12 changes: 11 additions & 1 deletion pg_shard.c
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Expand Up @@ -226,8 +226,18 @@ PgShardPlanner(Query *query, int cursorOptions, ParamListInfo boundParams)

ErrorIfQueryNotSupported(distributedQuery);

/* compute the list of shards this query needs to access */
/*
* Compute the list of shards this query needs to access.
* Error out if there are no existing shards for the table.
*/
queryShardList = DistributedQueryShardList(distributedQuery);
if (queryShardList == NIL)
{
ereport(ERROR, (errmsg("cannot plan SELECT query"),
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This message could be generated by an INSERT, UPDATE, or DELETE as well…

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Also, the style guide says this should be in past tense: could not plan query.

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I think we can use ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE here: we have an object (the distributed table) which hasn't been initialized yet (by creating shards). This code is used in PostgreSQL for other analogous situations, such as not calling nextval for a sequence before asking it what its current value is (grep for it).

errdetail("There are no existing shards for the distributed table."),
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The indentation here is off (should be aligned with parenthesis right before errmsg, not those before ERROR).

errhint("Run \"master_create_worker_shards\" to create shards "
"for the distributed table.")));
}

/*
* If a select query touches multiple shards, we don't push down the
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3 changes: 3 additions & 0 deletions sql/queries.sql
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Expand Up @@ -11,6 +11,9 @@ CREATE TABLE articles (

SELECT master_create_distributed_table('articles', 'author_id');

-- test when a table is distributed but no shards created yet
SELECT count(*) from articles;

\set VERBOSITY terse
SELECT master_create_worker_shards('articles', 2, 1);
\set VERBOSITY default
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