cartodb-postgresql/doc/CDB_SyncTable.md

Synchronize two tables. This function will synchronize a destination table with a source table. The idea is that the destination is a replica of source and source has been subject to modifications that are to be applied to destination.

This will be achieved by deleting the rows in the destination not present in the source, inserting rows of the source not in the destination and updating modified rows. If the destination table does not exist it will be created and all the rows of the source inserted into it.

Both tables must have a consistent cartodb_id primary key column which will be used to match the source and destination rows.

Note that both tables do not necessarily become identical after the synchronization, since additional columns may have been added to the destination; those columns will not be altered by the synchronization.

In addition some source columns may be skipped by listing them in the optional last argument; such columns will not be updated in the destination, so if they are present in it their values won't be altered.

Using the function

Import some data using COPY FROM into a temporary table, then synchronize a table with the data and finally delete the temporary table. This could be used import and update some data periodically while allowing to add columns to the data that will be preserved across updates.

CREATE tmp_pois(cartodb_id int, name text, type text, longitude double precision, latitude double precision, rank int);
COPY tmp_pois FROM '/tmp/pois.csv';
SELECT CDB_SyncTable('tmp_pois', 'public', 'pois');
DROP TABLE tmp_pois;

Now we could perform some changes to the pois to maintain our own ranking:

UPDATE pois SET rank = random()*4 + 1;

Then, if the source were updated at /tmp/pois.csv we could synchronize with it while preserving our rank values with:

CREATE tmp_pois(cartodb_id int, name text, type text, longitude double precision, latitude double precision, rank int);
COPY tmp_pois FROM '/tmp/pois.csv';
SELECT CDB_SyncTable('tmp_pois', 'public', 'pois', '{rank}');
DROP TABLE tmp_pois;

Arguments

CDB_SyncTable(src_table, dst_schema, dst_table, skip_cols)

• src_table REGCLASS the source data for the synchronization
• dst_scgena REGNAMESPACE the destination schema
• dst_table NAME the destination table to be updated
• skip_cols NAME[] an array of column names, empty by default, which will be skipped