OrientDB supports various methods to get the length of a collection or the length of a string, but I'm trying to determine the total size of a record in bytes. I can't find anything in the documentation or elsewhere that addresses this. Is it possible?
Answer from OrientDB's Luigi...
Create a function called "recordSize" (or something) with one input param (in this case record): return record.getSize();
Use it like this: select recordSize(#this) from...
Related
I'm trying to search for the items which's attribute matches the given function below in my large dataset, but I'm facing a problem here.
The row parameter only selects first 300 objects and the function then filters the matching results, but I'm trying to search the whole index, not only just first few, how can I rewrite this to achieve it?
having(
select(search(myIndex,q="*:*", fl="*", rows=300),
id,
dotProduct(ATTRIBUTE, array(4,5,2)) as prod,
l1norm(array(1,2,3)) as a,
l1norm(ATTRIBUTE) as b,
div(prod, add(a, sub(b, prod))) as c
), and(gteq(c, 5), lteq(c, 8)))
The simplest would be to increase the number of rows to cover the number of entries in the index.
However if this number is huge, you should probably use the /export request handler instead of a regular select-like handler.
The /export request handler allows a fully sorted result set to be
streamed out of Solr using a special rank query parser and
response writer. These have been specifically designed to work together to handle scenarios that involve sorting and exporting millions of records.
Depending on your needs, you could also do multiple queries playing with paginated results using both parameter start and rows, or if the number of entries is not known by the client code, use cursorMark.
I have a class that contains a LINKMAP field called links. This class is used recursively to create arbitrary hierarchical groupings (something like the time-series example, but not with the fixed year/month/day structure).
A query like this:
select expand(links['2017'].links['07'].links['15'].links['10'].links) from data where key='AAA'
Returns the actual records contained in the last layer of "links". This works exactly as expected.
But a query like this (note the 10,11 in the second to last layer of "links"):
select expand(links['2017'].links['07'].links['15'].links['10','11'].links) from data where key='AAA'
Returns two rows of the last layer of "links" instead:
{"1000":"#23:0","1001":"#24:0","1002":"#23:1"}
{"1003":"#24:1","1004":"#23:2"}
Using unionAll or intersect (with or without UNWIND) results in this single record:
[{"1000":"#23:0","1001":"#24:0","1002":"#23:1"},{"1003":"#24:1","1004":"#23:2"}]
But nothing I've tried (including various attempts at "compound" SELECTs) will get the expand to work as it does with the original example (i.e. return the actual records represented in the last LINKMAP).
Is there a SQL syntax that will achieve this?
Note: Even this (slightly modified) example from the ODB docs does not result in a list of linked records:
select expand(records) from
(select unionAll(years['2017'].links['07'].links['15'].links['10'].links, years['2017'].links['07'].links['15'].links['11'].links) as records from data where key='AAA')
Ref: https://orientdb.com/docs/2.2/Time-series-use-case.html
I'm not sure of what you want to achieve, but I think it's worth trying with values():
select expand(links['2017'].links['07'].links['15'].links['10','11'].links.values()) from data where key='AAA'
Given this perl DBI query:
$qh = $db_connection->prepare ('SELECT addresses.* from addresses WHERE 1');
The addresses table structure might change in the future, that is, some new columns may get inserted into it. So there's no guarantee which index number a particular column may get assigned to.
When I do a $qh->fetchrow_array, I want to be able to determine what the index number of a particular column is so I can check to see if it's empty. For example, I want to see if the mail_addr column is empty like so:
if (!$$row[$index_number]) {
do_something();
}
How can I determine what the value $index_number should be?
This can be determined via $sth->{NAME}. However, this situation is probably more appropriate for fetchrow_hashref which implements all the gluing of indices to field names you're looking for:
while ( my $row = $qh->fetchrow_hashref ) {
if (!$row->{mail_addr}) {
do_something();
}
}
Also consider the FetchHashKeyName attribute, fetchrow_hashref('NAME_lc'), or the $sth->{NAME_lc} attribute, which will guarantee the case of fieldnames presented by the DBI. Different SQL engines will normalize the identifier case differently, often depending on whether the identifier was quoted when declared.
Firstly, please don't use the $$row[$index_number] syntax. Anyone looking at your code will be expecting to see that written as $row->[$index_number].
You've worked out why SELECT * is a bad idea. So don't do that. List the specific columns that you are interested in - that way you can impose your own order (fetchrow_array returns columns in the order that they appear in the SELECT clause).
Alternatively, switch to one of the hash-based fetch methods like fetchrow_hashref.
But the best alternative would be to look at using DBIx::Class.
I need to know if the results of SQL query has been changed between two queries.
The solution a came up with is to calculate and compare some hash value based on ResultSet content.
What is the preferred way?
There are no such special hashCode method, for ResultSet that is calculated based on all retrieved data. Definetly you can not use default hashCode method.
To be 100% sure that you will take into account all the changes in the data,
you have to retrieve all columns from all the rows from ResultSet one by one and calculate hash code for them with any possible way. (Put everything into single String and get it's hashCode).
But it's very time consumption operation. I would propose you to execute extra query that calculate hash sum by itself. For example it can return count of rows and sum of all columns/rows... or smth like that..
Is there a way to retrieve (using a select statement) the size of a blob field in Firebird??
I've a field called "data" and I'd like to know the total size of all the records in the table.
Thanks.
I think you can use the OCTET_LENGTH() function.
You should also look at this answer it should be helpful.
If the field contains Images or another kind of data or even Text, you can use F_BLOBSIZE(blobfield) from FreeAdHocUDF
Input BLOB TextBLOb
For TextBLOb: returns the size/length (similar F_STRINGLENGTH)
For BinarBLOb: returns the size of file in byte