pg_dump: Fix dumping of inherited generated columns

Generation expressions of generated columns are always inherited, so
there is no need to set them separately in child tables, and there is
no syntax to do so either.  The code previously used the code paths
for the handling of default values, for which different rules apply;
in particular it might want to set a default value explicitly for an
inherited column.  This resulted in unrestorable dumps.  For generated
columns, just skip them in inherited tables.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/15830.1575468847%40sss.pgh.pa.us

1 files changed, 24 insertions, 7 deletions

diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index b0f02bc1f6e..1a261a55456 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -467,12 +467,22 @@ flagInhIndexes(Archive *fout, TableInfo tblinfo[], int numTables)
 /* flagInhAttrs -
  *	 for each dumpable table in tblinfo, flag its inherited attributes
  *
- * What we need to do here is detect child columns that inherit NOT NULL
- * bits from their parents (so that we needn't specify that again for the
- * child) and child columns that have DEFAULT NULL when their parents had
- * some non-null default.  In the latter case, we make up a dummy AttrDefInfo
- * object so that we'll correctly emit the necessary DEFAULT NULL clause;
- * otherwise the backend will apply an inherited default to the column.
+ * What we need to do here is:
+ *
+ * - Detect child columns that inherit NOT NULL bits from their parents, so
+ *   that we needn't specify that again for the child.
+ *
+ * - Detect child columns that have DEFAULT NULL when their parents had some
+ *   non-null default.  In this case, we make up a dummy AttrDefInfo object so
+ *   that we'll correctly emit the necessary DEFAULT NULL clause; otherwise
+ *   the backend will apply an inherited default to the column.
+ *
+ * - Detect child columns that have a generation expression when their parents
+ *   also have one.  Generation expressions are always inherited, so there is
+ *   no need to set them again in child tables, and there is no syntax for it
+ *   either.  (Exception: In binary upgrade mode we dump them because
+ *   inherited tables are recreated standalone first and then reattached to
+ *   the parent.)
  *
  * modifies tblinfo
  */
@@ -510,6 +520,7 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 		{
 			bool		foundNotNull;	/* Attr was NOT NULL in a parent */
 			bool		foundDefault;	/* Found a default in a parent */
+			bool		foundGenerated;	/* Found a generated in a parent */
 
 			/* no point in examining dropped columns */
 			if (tbinfo->attisdropped[j])
@@ -517,6 +528,7 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 
 			foundNotNull = false;
 			foundDefault = false;
+			foundGenerated = false;
 			for (k = 0; k < numParents; k++)
 			{
 				TableInfo  *parent = parents[k];
@@ -528,7 +540,8 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 				if (inhAttrInd >= 0)
 				{
 					foundNotNull |= parent->notnull[inhAttrInd];
-					foundDefault |= (parent->attrdefs[inhAttrInd] != NULL);
+					foundDefault |= (parent->attrdefs[inhAttrInd] != NULL && !parent->attgenerated[inhAttrInd]);
+					foundGenerated |= parent->attgenerated[inhAttrInd];
 				}
 			}
 
@@ -570,6 +583,10 @@ flagInhAttrs(DumpOptions *dopt, TableInfo *tblinfo, int numTables)
 
 				tbinfo->attrdefs[j] = attrDef;
 			}
+
+			/* Remove generation expression from child */
+			if (foundGenerated && !dopt->binary_upgrade)
+				tbinfo->attrdefs[j] = NULL;
 		}
 	}
 }