John Gage <jsmgage@xxxxxxxxxxxxxx> writes:
> This is a two-part question:
> 1) I have a source_text that I want to divide into smaller subunits
> that will be contained in rows in a column in a new table. Is it
> absolutely certain that the initial order of the rows in the resultant
> table after this operation:
> CREATE TABLE new_table AS SELECT regexp_split_to_table(source_text,
> E'regexp') as subunits FROM source_table;
> will be the same as the order of these subunits in the original text?
If you have a version new enough to have synchronize_seqscans, you'd
need to turn that off. Otherwise should be OK.
> 2) I would like to be able to create a serial-type column during
> CREATE TABLE AS in the new table that "memorizes" this order so that I
> can reconstruct the original text using ORDER BY on that serial
> column. However, I am stumped how to do that.
I think the trick is to get the SRF to be expanded before the serial
values are assigned. There's more than one way to do it, but I think
(too tired to experiment) this would work:
CREATE TABLE new_table (id serial, subunits text);
INSERT INTO new_table(subunits) SELECT regexp_split_to_table(source_text,
E'regexp') FROM source_table;
regards, tom lane
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