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table stats: automatic statistics on empty tables in some cases but not others #37362

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RaduBerinde opened this issue May 7, 2019 · 0 comments · Fixed by #37611
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table stats: automatic statistics on empty tables in some cases but not others #37362

RaduBerinde opened this issue May 7, 2019 · 0 comments · Fixed by #37611
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@rytaft

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@RaduBerinde
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I noticed the following behavior: if I create two empty tables, I don't get any statistics for them. But then if I create an index for one of them, that table does get statistics. At this point we have one table with statistics (which show 0 rows) and one without statistics (for which we assume 1000 rows). This leads to unexpected plans (e.g. lookup joins).

I am not sure if this is only a problem with empty tables, or also with tables that are small enough to not trigger the collection.

CC @awoods187
@rytaft rytaft mentioned this issue May 20, 2019
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rytaft added a commit to rytaft/cockroach that referenced this issue May 21, 2019
@rytaft
sql: always collect stats after a table is created
3aae09b 
Prior to this commit, we only collected automatic statistics on a
CREATE TABLE statement if it was of the form CREATE TABLE AS <query>.
To avoid inconsistencies, this commit changes the logic so we always
create statistics on every successful CREATE TABLE statement.

Fixes cockroachdb#37362

Release note (sql change): CREATE TABLE statements now always trigger automatic
statistics collection on the newly created table.
craig bot pushed a commit that referenced this issue May 21, 2019
@rytaft
Merge #37611
b4fabf9 
37611: sql: always collect stats after a table is created r=rytaft a=rytaft

Prior to this commit, we only collected automatic statistics on a
`CREATE TABLE` statement if it was of the form `CREATE TABLE AS <query>`.
To avoid inconsistencies, this commit changes the logic so we always
create statistics on every successful `CREATE TABLE` statement.

Fixes #37362

Release note (sql change): CREATE TABLE statements now always trigger automatic
statistics collection on the newly created table.

Co-authored-by: Rebecca Taft <[email protected]>
@craig craig bot closed this as completed in #37611 May 21, 2019
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sql: always collect stats after a table is created rytaft/cockroach
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@rytaft @RaduBerinde