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commit    d5a905ed5e7b277392db6c07efd40ec2ba9e6341
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Tue Mar 23 18:27:50 2021 +0000
First released in: 14.0, 9.6.22, 10.17, 11.12, 12.7, 13.3

    Fix psql's \connect command some more.
    
    Jasen Betts reported yet another unintended side effect of commit
    85c54287a: reconnecting with "\c service=whatever" did not have the
    expected results.  The reason is that starting from the output of
    PQconndefaults() effectively allows environment variables (such
    as PGPORT) to override entries in the service file, whereas the
    normal priority is the other way around.
    
    Not using PQconndefaults at all would require yet a third main code
    path in do_connect's parameter setup, so I don't really want to fix
    it that way.  But we can have the logic effectively ignore all the
    default values for just a couple more lines of code.
    
    This patch doesn't change the behavior for "\c -reuse-previous=on
    service=whatever".  That remains significantly different from before
    85c54287a, because many more parameters will be re-used, and thus
    not be possible for service entries to replace.  But I think this
    is (mostly?) intentional.  In any case, since libpq does not report
    where it got parameter values from, it's hard to do differently.
    
    Per bug #16936 from Jasen Betts.  As with the previous patches,
    back-patch to all supported branches.  (9.5 is unfortunately now
    out of support, so this won't get fixed there.)
    
    Discussion: https://postgr.es/m/16936-3f524322a53a29f0@postgresql.org


 src/bin/psql/command.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a840ac18721..2ea5ba8fc49 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -3096,6 +3096,25 @@ do_connect(enum trivalue reuse_previous_specification,
 						if (strcmp(replci->keyword, "password") == 0)
 							have_password = true;
 					}
+					else if (!reuse_previous)
+					{
+						/*
+						 * When we have a connstring and are not re-using
+						 * parameters, swap *all* entries, even those not set
+						 * by the connstring.  This avoids absorbing
+						 * environment-dependent defaults from the result of
+						 * PQconndefaults().  We don't want to do that because
+						 * they'd override service-file entries if the
+						 * connstring specifies a service parameter, whereas
+						 * the priority should be the other way around.  libpq
+						 * can certainly recompute any defaults we don't pass
+						 * here.  (In this situation, it's a bit wasteful to
+						 * have called PQconndefaults() at all, but not doing
+						 * so would require yet another major code path here.)
+						 */
+						replci->val = ci->val;
+						ci->val = NULL;
+					}
 				}
 				Assert(ci->keyword == NULL && replci->keyword == NULL);
 


[parent: fb742ce2687a]