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Up to now, to create such a function, one had to make a pg_proc.dat entry and then overwrite it with a CREATE OR REPLACE command in system_functions.sql. That's error-prone (cf. bug #19409) and results in leaving dead rows in the initial contents of pg_proc. Manual maintenance of pg_node_tree strings seems entirely impractical, and parsing expressions during bootstrap would be extremely difficult as well. But Andres Freund observed that all the current use-cases are simple constants, and building a Const node is well within the capabilities of bootstrap mode. So this patch invents a special case: if bootstrap mode is asked to ingest a non-null value for pg_proc.proargdefaults (which would otherwise fail in pg_node_tree_in), it parses the value as an array literal and then feeds the element strings to the input functions for the corresponding parameter types. Then we can build a suitable pg_node_tree string with just a few more lines of code. This allows removing all the system_functions.sql entries that are just there to set up default arguments, replacing them with proargdefaults fields in pg_proc.dat entries. The old technique remains available in case someone needs a non-constant default. The initial contents of pg_proc are demonstrably the same after this patch, except that (1) json_strip_nulls and jsonb_strip_nulls now have the correct provolatile setting, as per bug #19409; (2) pg_terminate_backend, make_interval, and drandom_normal now have defaults that don't include a type coercion, which is how they should have been all along. In passing, remove some unused entries from bootstrap.c's TypInfo[] array. I had to add some new ones because we'll now need an entry for each default-possessing system function parameter, but we shouldn't carry more than we need there; it's just a maintenance gotcha. Bug: #19409 Reported-by: Lucio Chiessi <lucio.chiessi@trustly.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Author: Andrew Dunstan <andrew@dunslane.net> Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/183292bb-4891-4c96-a3ca-e78b5e0e1358@dunslane.net Discussion: https://postgr.es/m/19409-e16cd2605e59a4af@postgresql.org |
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