StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
primarykey
Id
17602580
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
2
CommunityOwnedDate
CreationDate
2013-07-11T20:12:20.407
FavoriteCount
0
LastActivityDate
2013-07-12T12:30:57.557
LastEditDate
2013-07-12T12:30:57.557
LastEditorUserId
131874
OwnerUserId
131874
ParentId
17601719
PostTypeId
2
Score
4
ViewCount
0
LastEditorDisplayName
text
Body
If you change the function you will have to rebuild the index. <pre><code>create table t (i integer); insert into t (i) select generate_series(1, 100000); analyze t; </code></pre> A simple function to return the opposite integer: <pre><code>create or replace function f(i integer) returns integer as $$ select i * -1; $$ immutable language sql; </code></pre> And the index on it: <pre><code>create index t_i_index on t(f(i)); </code></pre> The index is used: <pre><code>explain select * from t order by f(i); QUERY PLAN --------------------------------------------------------------------------- Index Scan using t_i_index on t (cost=0.00..3300.26 rows=100000 width=4) </code></pre> Now the function is changed to return the integer itself: <pre><code>create or replace function f(i integer) returns integer as $$ select i; $$ immutable language sql; </code></pre> And the index is not used anymore: <pre><code>explain select * from t order by f(i); QUERY PLAN --------------------------------------------------------------- Sort (cost=11116.32..11366.32 rows=100000 width=4) Sort Key: i -> Seq Scan on t (cost=0.00..1443.00 rows=100000 width=4) </code></pre> If the index is rebuilt <pre><code>reindex index t_i_index; </code></pre> It is used again: <pre><code>explain select * from t order by f(i); QUERY PLAN --------------------------------------------------------------------------- Index Scan using t_i_index on t (cost=0.00..4376.26 rows=100000 width=4) </code></pre>
Tags
Title
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. POReplace function used in index
 singulars
 PostTypePostTypeId
 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USClodoaldo Neto
UserOwnerUserId
1. USClodoaldo Neto
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. This table or related slice is empty.
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 PO
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId
1. COOkay, not unexpected. I expect a 'REINDEX' would also convince the planner to again use the index, no?
 singulars
 PostPostId
 PO
 UserUserId
 USDylan Hettinger
2. CO@Dylan Yes reindex works and is simpler. I have updated the answer.
 singulars
 PostPostId
 PO
 UserUserId
 USClodoaldo Neto

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.