Fix RLS with COPY (col1, col2) FROM tab

Attempting to COPY a subset of columns from a table with RLS enabled
would fail due to an invalid query being constructed (using a single
ColumnRef with the list of fields to exact in 'fields', but that's for
the different levels of an indirection for a single column, not for
specifying multiple columns).

Correct by building a ColumnRef and then RestTarget for each column
being requested and then adding those to the targetList for the select
query.  Include regression tests to hopefully catch if this is broken
again in the future.

Patch-By: Adam Brightwell
Reviewed-By: Michael Paquier

1 files changed, 51 insertions, 12 deletions

diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 432b0ca67ba..457c9bbd74b 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -871,6 +871,7 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt, uint64 *processed)
 			ColumnRef  *cr;
 			ResTarget  *target;
 			RangeVar   *from;
+			List	   *targetList = NIL;
 
 			if (is_from)
 				ereport(ERROR,
@@ -878,21 +879,59 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt, uint64 *processed)
 				   errmsg("COPY FROM not supported with row-level security"),
 						 errhint("Use INSERT statements instead.")));
 
-			/* Build target list */
-			cr = makeNode(ColumnRef);
-
+			/*
+			 * Build target list
+			 *
+			 * If no columns are specified in the attribute list of the COPY
+			 * command, then the target list is 'all' columns. Therefore, '*'
+			 * should be used as the target list for the resulting SELECT
+			 * statement.
+			 *
+			 * In the case that columns are specified in the attribute list,
+			 * create a ColumnRef and ResTarget for each column and add them to
+			 * the target list for the resulting SELECT statement.
+			 */
 			if (!stmt->attlist)
+			{
+				cr = makeNode(ColumnRef);
 				cr->fields = list_make1(makeNode(A_Star));
-			else
-				cr->fields = stmt->attlist;
+				cr->location = -1;
+
+				target = makeNode(ResTarget);
+				target->name = NULL;
+				target->indirection = NIL;
+				target->val = (Node *) cr;
+				target->location = -1;
 
-			cr->location = 1;
+				targetList = list_make1(target);
+			}
+			else
+			{
+				ListCell   *lc;
 
-			target = makeNode(ResTarget);
-			target->name = NULL;
-			target->indirection = NIL;
-			target->val = (Node *) cr;
-			target->location = 1;
+				foreach(lc, stmt->attlist)
+				{
+					/*
+					 * Build the ColumnRef for each column.  The ColumnRef
+					 * 'fields' property is a String 'Value' node (see
+					 * nodes/value.h) that corresponds to the column name
+					 * respectively.
+					 */
+					cr = makeNode(ColumnRef);
+					cr->fields = list_make1(lfirst(lc));
+					cr->location = -1;
+
+					/* Build the ResTarget and add the ColumnRef to it. */
+					target = makeNode(ResTarget);
+					target->name = NULL;
+					target->indirection = NIL;
+					target->val = (Node *) cr;
+					target->location = -1;
+
+					/* Add each column to the SELECT statement's target list */
+					targetList = lappend(targetList, target);
+				}
+			}
 
 			/*
 			 * Build RangeVar for from clause, fully qualified based on the
@@ -903,7 +942,7 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt, uint64 *processed)
 
 			/* Build query */
 			select = makeNode(SelectStmt);
-			select->targetList = list_make1(target);
+			select->targetList = targetList;
 			select->fromClause = list_make1(from);
 
 			query = (Node *) select;