Thread: BUG #18340: BitString may break nodetoString() conversion for a raw parse tree

The following bug has been logged on the website:

Bug reference:      18340
Logged by:          Alexander Lakhin
Email address:      exclusion@gmail.com
PostgreSQL version: 16.2
Operating system:   Ubuntu 22.04
Description:

When a server compiled with -DWRITE_READ_PARSE_PLAN_TREES, the following
query:
SELECT x' 0';
produces:
ERROR:  did not find '}' at end of input node

Observed starting from commit 40ad8f9de, which implemented
WRITE_READ_PARSE_PLAN_TREES for raw parse trees.

More interesting results may be obtained (e.g.,
WARNING:  outfuncs/readfuncs failed to produce an equal raw parse tree
), but with raw trees only, not with node trees stored in the database,
considering core code.

Still codesearch.debian.net shows that nodeToString() used by several
extensions: pg_qual_stats, pgpool2, hypopg, pglogical; perhaps some of
them use that conversion unsafely (without processing a node with
transformExpr() or so).

PG Bug reporting form <noreply@postgresql.org> writes:
> When a server compiled with -DWRITE_READ_PARSE_PLAN_TREES, the following
> query:
> SELECT x' 0';
> produces:
> ERROR:  did not find '}' at end of input node

> Observed starting from commit 40ad8f9de, which implemented
> WRITE_READ_PARSE_PLAN_TREES for raw parse trees.

Bleah.  That's presumably my fault, will take a look.

> More interesting results may be obtained (e.g.,
> WARNING:  outfuncs/readfuncs failed to produce an equal raw parse tree
> ), but with raw trees only, not with node trees stored in the database,
> considering core code.
> Still codesearch.debian.net shows that nodeToString() used by several
> extensions: pg_qual_stats, pgpool2, hypopg, pglogical; perhaps some of
> them use that conversion unsafely (without processing a node with
> transformExpr() or so).

I doubt there's any reason to consider this a critical problem
right now.  We should fix it of course, in the expectation that
we might need it to work someday.

            regards, tom lane