Unique – Guarantees unique values for the column(or set of columns) included in the index Covering – Includes all of the columns that are used in a particular query (or set of queries), allowing the database to use only the index and not actually have to look at the table data to retrieve the results … Read more
Example of selecting from a DataFrame with the use of index: from numpy.random import randn from pandas import DataFrame from datetime import timedelta as td import dateutil.parser d = dateutil.parser.parse(“2014-01-01”) df = DataFrame(randn(6,2), columns=list(‘AB’), index=[d + td(days=x) for x in range(1,7)]) In [1]: df Out[1]: A B 2014-01-02 -1.172285 1.706200 2014-01-03 0.039511 -0.320798 2014-01-04 -0.192179 … Read more
It is difficult to imagine real-world scenarios where indexing every column would be useful, for the reasons mentioned above. The type of scenario would require a bunch of different queries, all accessing exactly one column of the table. Each query could be accessing a different column. The other answers don’t address the issues during the … Read more
To locate broken index use: select index_name,index_type,status,domidx_status,domidx_opstatus from user_indexes where index_type like ‘%DOMAIN%’ and (domidx_status <> ‘VALID’ or domidx_opstatus <> ‘VALID’); To rebuild the index use: alter index INDEX_NAME rebuild;
There are a few alternatives. The below assumes you are iterating over a 1d NumPy array. Iterate with range for j in range(theta.shape[0]): # or range(len(theta)) some_function(j, theta[j], theta) Note this is the only of the 3 solutions which will work with numba. This is noteworthy since iterating over a NumPy array explicitly is usually … Read more
Basically, NULL values occupy 1 bit in the NULL bitmap. But it’s not that simple. The null bitmap (per row) is only allocated if at least one column in that row holds a NULL value. This can lead to a seemingly paradoxic effect in tables with 9 or more columns: assigning the first NULL value … Read more
For a query like this, a partial index covering only unsynced rows would serve best. CREATE INDEX ON tbl (id) WHERE sync_done = FALSE; However, for a use case like this, other synchronization methods may be preferable to begin with: Have a look at LISTEN / NOTIFY. Or use a trigger in combination with dblink … Read more
Welcome to a world with Java 8! It only took me all night with no sleep to learn what was needed to write this one freaking line of code. I’m sure it is already out there somewhere but I couldn’t find it. So I’m sharing my hours and hours of research, enjoy. Woot! Assuming: ArrayList<ArrayList<String>> … Read more