Thread: index row size 2720 exceeds btree version 4

Am 10.08.22 06:57 schrieb(en) Daulat:
> We are facing an error while uploading data in a table that has two B-tree
> indexes. As per the Postgres documentation there is a limitation of b-tree
> index size but I need to know if there is any alternative to overcome this
> issue.
[snip]
> UNIQUE INDEX uk_gvoa_gi_ad ON test.groupedvuln_asset USING btree (group_id,
> hostip, macaddress, fqdn, scanid)"

I had a similar issue, which I solved by creating an index on the hash of the concatenation of the items, i.e.
somethinglike 

CREATE UNIQUE INDEX uk_gvoa_gi_ad ON test.groupedvuln_asset
     USING btree (sha256(group_id::bytea || hostip::bytea || macaddress::bytea || fqdn::bytea || scanid::bytea));

Not guaranteed to be 100% collision free, though, but should be sufficient for most real-world use cases.

Hth,
Albrecht.

On 2022-08-10 10:27:46 +0530, Daulat wrote:
> Error:
>
> " index row size 2720 exceeds btree version 4 maximum 2704 for index
> ""uk_gvoa_gi_ad"" 54000"
> uk_gvoa_gi_ad
>
> Index:
>
> UNIQUE INDEX pk_gvoa_id ON test.groupedvuln_asset USING btree
> (groupedvuln_orphanasset_id)"
>
> UNIQUE INDEX uk_gvoa_gi_ad ON test.groupedvuln_asset USING btree (group_id,
> hostip, macaddress, fqdn, scanid)"

How are those fields defined? I would expect a group id to be 4 or 8
bytes, a host ip 16 bytes, a mac address 6 bytes and an fqdn at most 255
bytes. So without the scan id we are at 285 bytes. maybe a bit more due
to overhead. That leaves about 2400 bytes for the scan id. I don't know
what a scanid is, but 2000+ bytes for an id seems excessive.

        hp

--
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp@hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"