128dd9f9ec
As it stands, flagInhAttrs() can make changes in table properties that change decisions made at other tables during other iterations of its loop. This is a pretty bad idea, since we visit the tables in OID order which is not necessarily related to inheritance relationships. So far as I can tell, the consequences are just cosmetic: we might dump DEFAULT or GENERATED expressions that we don't really need to because they match properties of the parent. Nonetheless, it's buggy, and somebody might someday add functionality here that fails less benignly when the traversal order varies. One issue is that when we decide we needn't dump a particular GENERATED expression, we physically unlink the struct for it, so that it will now look like the table has no such expression, causing the wrong choice to be made at any child visited later. We can improve that by instead clearing the dobj.dump flag, and taking care to check that flag when it comes time to dump the expression or not. The other problem is that if we decide we need to fake up a DEFAULT NULL clause to override a default that would otherwise get inherited, we modify the data structure in the reverse fashion, creating an attrdefs entry where there hadn't been one. It's harder to avoid doing that, but since the backend won't report a plain "DEFAULT NULL" property we can modify the code to recognize ones we just added. Add some commentary to perhaps forestall future mistakes of the same ilk. Since the effects of this seem only cosmetic, no back-patch. Discussion: https://postgr.es/m/1506298.1676323579@sss.pgh.pa.us
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