Insert

The insert method of DataJoint table objects inserts entities into the table.

The insert method inserts any number of entities in the form of a structure array with field names corresponding to the attribute names.

For example

s.username = 'alice';
s.first_name = 'Alice';
s.last_name = 'Cooper';
insert(lab.Person, s)

Quick entry of multiple entities takes advantage of MATLAB’s cell array notation:

insert(lab.Person, {
       'alice'   'Alice'   'Cooper'
       'bob'     'Bob'     'Dylan'
       'carol'   'Carol'   'Douglas'
})

In this case, the values must match the order of the attributes in the table.

The optional parameter command can be either 'IGNORE' or 'REPLACE'. Duplicates, unmatched attributes, or missing required attributes will cause insert errors, unless command is specified.

Batched inserts

Inserting a set of entities in a single insert differs from inserting the same set of entities one-by-one in a for loop in two ways:

  1. Network overhead is reduced. Network overhead can be tens of milliseconds per query. Inserting 1000 entities in a single insert call may save a few seconds over inserting them individually.
  2. The insert is performed as an all-or-nothing transaction. If even one insert fails because it violates any constraint, then none of the entities in the set are inserted.

However, inserting too many entities in a single query may run against buffer size or packet size limits of the database server. Due to these limitations, performing inserts of very large numbers of entities should be broken up into moderately sized batches, such as a few hundred at a time.

Server-side inserts

Data inserted into a table often come from other tables already present on the database server. In such cases, data can be fetched from the first table and then inserted into another table, but this results in transfers back and forth between the database and the local system. Instead, data can be inserted from one table into another without transfers between the database and the local system using queries.

In the example below, a new schema has been created in preparation for phase two of a project. Experimental protocols from the first phase of the project will be reused in the second phase. Since the entities are already present on the database in the Protocol table of the phase_one schema, we can perform a server-side insert into phase_two.Protocol without fetching a local copy.

% Server-side inserts are faster...
phase_two.Protocol.insert(phase_one.Protocol)

% ...than fetching before inserting
protocols = phase_one.Protocol.fetch();
phase_two.Protocol.insert(protocols)