Make pg_dump emit ATTACH PARTITION instead of PARTITION OF

Using PARTITION OF can result in column ordering being changed from the
database being dumped, if the partition uses a column layout different
from the parent's.  It's not pg_dump's job to editorialize on table
definitions, so this is not acceptable; back-patch all the way back to
pg10, where partitioned tables where introduced.

This change also ensures that partitions end up in the correct
tablespace, if different from the parent's; this is an oversight in
ca41030 (in pg12 only).  Partitioned indexes (in pg11) don't have
this problem, because they're already created as independent indexes and
attached to their parents afterwards.

This change also has the advantage that the partition is restorable from
the dump (as a standalone table) even if its parent table isn't
restored.

Author: David Rowley
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/CAKJS1f_1c260nOt_vBJ067AZ3JXptXVRohDVMLEBmudX1YEx-A@mail.gmail.com
Discussion: https://postgr.es/m/20190423185007.GA27954@alvherre.pgsql

Author: alvherre

src/bin/pg_dump/pg_dump.c

@@ -8618,9 +8618,12 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
  * Normally this is always true, but it's false for dropped columns, as well
  * as those that were inherited without any local definition.  (If we print
  * such a column it will mistakenly get pg_attribute.attislocal set to true.)
- * However, in binary_upgrade mode, we must print all such columns anyway and
- * fix the attislocal/attisdropped state later, so as to keep control of the
- * physical column order.
+ * For partitions, it's always true, because we want the partitions to be
+ * created independently and ATTACH PARTITION used afterwards.
+ *
+ * In binary_upgrade mode, we must print all columns and fix the attislocal/
+ * attisdropped state later, so as to keep control of the physical column
+ * order.
  *
  * This function exists because there are scattered nonobvious places that
  * must be kept in sync with this decision.
@@ -8630,7 +8633,9 @@ shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno)
 {
 	if (dopt->binary_upgrade)
 		return true;
-	return (tbinfo->attislocal[colno] && !tbinfo->attisdropped[colno]);
+	if (tbinfo->attisdropped[colno])
+		return false;
+	return (tbinfo->attislocal[colno] || tbinfo->ispartition);
 }
 
 
@@ -15599,27 +15604,6 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 		if (tbinfo->reloftype && !dopt->binary_upgrade)
 			appendPQExpBuffer(q, " OF %s", tbinfo->reloftype);
 
-		/*
-		 * If the table is a partition, dump it as such; except in the case of
-		 * a binary upgrade, we dump the table normally and attach it to the
-		 * parent afterward.
-		 */
-		if (tbinfo->ispartition && !dopt->binary_upgrade)
-		{
-			TableInfo  *parentRel = tbinfo->parents[0];
-
-			/*
-			 * With partitions, unlike inheritance, there can only be one
-			 * parent.
-			 */
-			if (tbinfo->numParents != 1)
-				fatal("invalid number of parents %d for table \"%s\"",
-							  tbinfo->numParents, tbinfo->dobj.name);
-
-			appendPQExpBuffer(q, " PARTITION OF %s",
-							  fmtQualifiedDumpable(parentRel));
-		}
-
 		if (tbinfo->relkind != RELKIND_MATVIEW)
 		{
 			/* Dump the attributes */
@@ -15648,12 +15632,9 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 											   (!tbinfo->inhNotNull[j] ||
 												dopt->binary_upgrade));
 
-					/*
-					 * Skip column if fully defined by reloftype or the
-					 * partition parent.
-					 */
-					if ((tbinfo->reloftype || tbinfo->ispartition) &&
-						!has_default && !has_notnull && !dopt->binary_upgrade)
+					/* Skip column if fully defined by reloftype */
+					if (tbinfo->reloftype && !has_default && !has_notnull &&
+						!dopt->binary_upgrade)
 						continue;
 
 					/* Format properly if not first attr */
@@ -15676,20 +15657,16 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 						 * clean things up later.
 						 */
 						appendPQExpBufferStr(q, " INTEGER /* dummy */");
-						/* Skip all the rest, too */
+						/* and skip to the next column */
 						continue;
 					}
 
 					/*
-					 * Attribute type
-					 *
-					 * In binary-upgrade mode, we always include the type. If
-					 * we aren't in binary-upgrade mode, then we skip the type
-					 * when creating a typed table ('OF type_name') or a
-					 * partition ('PARTITION OF'), since the type comes from
-					 * the parent/partitioned table.
+					 * Attribute type; print it except when creating a typed
+					 * table ('OF type_name'), but in binary-upgrade mode,
+					 * print it in that case too.
 					 */
-					if (dopt->binary_upgrade || (!tbinfo->reloftype && !tbinfo->ispartition))
+					if (dopt->binary_upgrade || !tbinfo->reloftype)
 					{
 						appendPQExpBuffer(q, " %s",
 										  tbinfo->atttypnames[j]);
@@ -15746,25 +15723,20 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 
 			if (actual_atts)
 				appendPQExpBufferStr(q, "\n)");
-			else if (!((tbinfo->reloftype || tbinfo->ispartition) &&
-					   !dopt->binary_upgrade))
+			else if (!(tbinfo->reloftype && !dopt->binary_upgrade))
 			{
 				/*
-				 * We must have a parenthesized attribute list, even though
-				 * empty, when not using the OF TYPE or PARTITION OF syntax.
+				 * No attributes? we must have a parenthesized attribute list,
+				 * even though empty, when not using the OF TYPE syntax.
 				 */
 				appendPQExpBufferStr(q, " (\n)");
 			}
 
-			if (tbinfo->ispartition && !dopt->binary_upgrade)
-			{
-				appendPQExpBufferChar(q, '\n');
-				appendPQExpBufferStr(q, tbinfo->partbound);
-			}
-
-			/* Emit the INHERITS clause, except if this is a partition. */
-			if (numParents > 0 &&
-				!tbinfo->ispartition &&
+			/*
+			 * Emit the INHERITS clause (not for partitions), except in
+			 * binary-upgrade mode.
+			 */
+			if (numParents > 0 && !tbinfo->ispartition &&
 				!dopt->binary_upgrade)
 			{
 				appendPQExpBufferStr(q, "\nINHERITS (");
@@ -15937,30 +15909,16 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 				appendPQExpBufferStr(q, "::pg_catalog.regclass;\n");
 			}
 
-			if (numParents > 0)
+			if (numParents > 0 && !tbinfo->ispartition)
 			{
-				appendPQExpBufferStr(q, "\n-- For binary upgrade, set up inheritance and partitioning this way.\n");
+				appendPQExpBufferStr(q, "\n-- For binary upgrade, set up inheritance this way.\n");
 				for (k = 0; k < numParents; k++)
 				{
 					TableInfo  *parentRel = parents[k];
 
-					/* In the partitioning case, we alter the parent */
-					if (tbinfo->ispartition)
-						appendPQExpBuffer(q,
-										  "ALTER TABLE ONLY %s ATTACH PARTITION ",
-										  fmtQualifiedDumpable(parentRel));
-					else
-						appendPQExpBuffer(q, "ALTER TABLE ONLY %s INHERIT ",
-										  qualrelname);
-
-					/* Partition needs specifying the bounds */
-					if (tbinfo->ispartition)
-						appendPQExpBuffer(q, "%s %s;\n",
-										  qualrelname,
-										  tbinfo->partbound);
-					else
-						appendPQExpBuffer(q, "%s;\n",
-										  fmtQualifiedDumpable(parentRel));
+					appendPQExpBuffer(q, "ALTER TABLE ONLY %s INHERIT %s;\n",
+									  qualrelname,
+									  fmtQualifiedDumpable(parentRel));
 				}
 			}
 
@@ -15973,6 +15931,27 @@ dumpTableSchema(Archive *fout, TableInfo *tbinfo)
 			}
 		}
 
+		/*
+		 * For partitioned tables, emit the ATTACH PARTITION clause.  Note
+		 * that we always want to create partitions this way instead of using
+		 * CREATE TABLE .. PARTITION OF, mainly to preserve a possible column
+		 * layout discrepancy with the parent, but also to ensure it gets the
+		 * correct tablespace setting if it differs from the parent's.
+		 */
+		if (tbinfo->ispartition)
+		{
+			/* With partitions there can only be one parent */
+			if (tbinfo->numParents != 1)
+				fatal("invalid number of parents %d for table \"%s\"",
+					  tbinfo->numParents, tbinfo->dobj.name);
+
+			/* Perform ALTER TABLE on the parent */
+			appendPQExpBuffer(q,
+							  "ALTER TABLE ONLY %s ATTACH PARTITION %s %s;\n",
+							  fmtQualifiedDumpable(parents[0]),
+							  qualrelname, tbinfo->partbound);
+		}
+
 		/*
 		 * In binary_upgrade mode, arrange to restore the old relfrozenxid and
 		 * relminmxid of all vacuumable relations.  (While vacuum.c processes

src/bin/pg_dump/t/002_pg_dump.pl

@@ -733,7 +733,12 @@
 			\QALTER TABLE ONLY dump_test.measurement ATTACH PARTITION dump_test_second_schema.measurement_y2006m2 \E
 			\QFOR VALUES FROM ('2006-02-01') TO ('2006-03-01');\E\n
 			/xm,
-		like => { binary_upgrade => 1, },
+		like => {
+			%full_runs,
+			role             => 1,
+			section_pre_data => 1,
+			binary_upgrade   => 1,
+		},
 	  },
 
 	'ALTER TABLE test_table CLUSTER ON test_table_pkey' => {
@@ -2322,12 +2327,13 @@
 			\)\n
 			\QFOR VALUES FROM ('2006-02-01') TO ('2006-03-01');\E\n
 			/xm,
-		like => {
+		like   => {},
+		unlike => {
 			%full_runs,
 			role             => 1,
 			section_pre_data => 1,
+			binary_upgrade   => 1,
 		},
-		unlike => { binary_upgrade => 1, },
 	},
 
 	'CREATE TABLE test_fourth_table_zero_col' => {