Be more careful about printing constants in ruleutils.c.

The previous coding in get_const_expr() tried to avoid quoting integer,
float, and numeric literals if at all possible.  While that looks nice,
it means that dumped expressions might re-parse to something that's
semantically equivalent but not the exact same parsetree; for example
a FLOAT8 constant would re-parse as a NUMERIC constant with a cast to
FLOAT8.  Though the result would be the same after constant-folding,
this is problematic in certain contexts.  In particular, Jeff Davis
pointed out that this could cause unexpected failures in ALTER INHERIT
operations because of child tables having not-exactly-equivalent CHECK
expressions.  Therefore, favor correctness over legibility and dump
such constants in quotes except in the limited cases where they'll
be interpreted as the same type even without any casting.

This results in assorted small changes in the regression test outputs,
and will affect display of user-defined views and rules similarly.
The odds of that causing problems in the field seem non-negligible;
given the lack of previous complaints, it seems best not to change
this in the back branches.

Author: tglsfdc

contrib/btree_gist/expected/float4.out

@@ -78,7 +78,7 @@ SELECT a, a <-> '-179.0' FROM float4tmp ORDER BY a <-> '-179.0' LIMIT 3;
 ----------------------------------------------------
  Limit
    ->  Index Only Scan using float4idx on float4tmp
-         Order By: (a <-> (-179)::real)
+         Order By: (a <-> '-179'::real)
 (3 rows)
 
 SELECT a, a <-> '-179.0' FROM float4tmp ORDER BY a <-> '-179.0' LIMIT 3;

contrib/btree_gist/expected/float8.out

@@ -78,7 +78,7 @@ SELECT a, a <-> '-1890.0' FROM float8tmp ORDER BY a <-> '-1890.0' LIMIT 3;
 -----------------------------------------------------
  Limit
    ->  Index Only Scan using float8idx on float8tmp
-         Order By: (a <-> (-1890)::double precision)
+         Order By: (a <-> '-1890'::double precision)
 (3 rows)
 
 SELECT a, a <-> '-1890.0' FROM float8tmp ORDER BY a <-> '-1890.0' LIMIT 3;

contrib/btree_gist/expected/int2.out

@@ -78,7 +78,7 @@ SELECT a, a <-> '237' FROM int2tmp ORDER BY a <-> '237' LIMIT 3;
 ------------------------------------------------
  Limit
    ->  Index Only Scan using int2idx on int2tmp
-         Order By: (a <-> 237::smallint)
+         Order By: (a <-> '237'::smallint)
 (3 rows)
 
 SELECT a, a <-> '237' FROM int2tmp ORDER BY a <-> '237' LIMIT 3;

contrib/btree_gist/expected/int8.out

@@ -74,11 +74,11 @@ SELECT count(*) FROM int8tmp WHERE a >  464571291354841::int8;
 
 EXPLAIN (COSTS OFF)
 SELECT a, a <-> '464571291354841' FROM int8tmp ORDER BY a <-> '464571291354841' LIMIT 3;
-                    QUERY PLAN                     
----------------------------------------------------
+                     QUERY PLAN                      
+-----------------------------------------------------
  Limit
    ->  Index Only Scan using int8idx on int8tmp
-         Order By: (a <-> 464571291354841::bigint)
+         Order By: (a <-> '464571291354841'::bigint)
 (3 rows)
 
 SELECT a, a <-> '464571291354841' FROM int8tmp ORDER BY a <-> '464571291354841' LIMIT 3;

contrib/btree_gist/expected/numeric.out

@@ -190,12 +190,12 @@ SELECT count(*) FROM numerictmp WHERE a >  0 ;
 SET enable_bitmapscan=off;
 EXPLAIN (COSTS OFF)
 SELECT * FROM numerictmp WHERE a BETWEEN 1 AND 300 ORDER BY a;
-                           QUERY PLAN                            
------------------------------------------------------------------
+                             QUERY PLAN                              
+---------------------------------------------------------------------
  Sort
    Sort Key: a
    ->  Index Only Scan using numericidx on numerictmp
-         Index Cond: ((a >= 1::numeric) AND (a <= 300::numeric))
+         Index Cond: ((a >= '1'::numeric) AND (a <= '300'::numeric))
 (4 rows)
 
 SELECT * FROM numerictmp WHERE a BETWEEN 1 AND 300 ORDER BY a;

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -874,7 +874,7 @@ SELECT * FROM ft1 t1 WHERE t1.tableoid = 'pg_class'::regclass LIMIT 1;
    Output: c1, c2, c3, c4, c5, c6, c7, c8
    ->  Foreign Scan on public.ft1 t1
          Output: c1, c2, c3, c4, c5, c6, c7, c8
-         Filter: (t1.tableoid = 1259::oid)
+         Filter: (t1.tableoid = '1259'::oid)
          Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
 (6 rows)
 

src/backend/utils/adt/ruleutils.c

@@ -15,6 +15,7 @@
  */
 #include "postgres.h"
 
+#include <ctype.h>
 #include <unistd.h>
 #include <fcntl.h>
 
@@ -7977,6 +7978,13 @@ get_coercion_expr(Node *arg, deparse_context *context,
 	 * right above it.  Avoid generating redundant output. However, beware of
 	 * suppressing casts when the user actually wrote something like
 	 * 'foo'::text::char(3).
+	 *
+	 * Note: it might seem that we are missing the possibility of needing to
+	 * print a COLLATE clause for such a Const.  However, a Const could only
+	 * have nondefault collation in a post-constant-folding tree, in which the
+	 * length coercion would have been folded too.  See also the special
+	 * handling of CollateExpr in coerce_to_target_type(): any collation
+	 * marking will be above the coercion node, not below it.
 	 */
 	if (arg && IsA(arg, Const) &&
 		((Const *) arg)->consttype == resulttype &&
@@ -8007,8 +8015,9 @@ get_coercion_expr(Node *arg, deparse_context *context,
  * the right type by default.
  *
  * If the Const's collation isn't default for its type, show that too.
- * This can only happen in trees that have been through constant-folding.
- * We assume we don't need to do this when showtype is -1.
+ * We mustn't do this when showtype is -1 (since that means the caller will
+ * print "::typename", and we can't put a COLLATE clause in between).  It's
+ * caller's responsibility that collation isn't missed in such cases.
  * ----------
  */
 static void
@@ -8018,8 +8027,7 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
 	Oid			typoutput;
 	bool		typIsVarlena;
 	char	   *extval;
-	bool		isfloat = false;
-	bool		needlabel;
+	bool		needlabel = false;
 
 	if (constval->constisnull)
 	{
@@ -8045,40 +8053,42 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
 
 	switch (constval->consttype)
 	{
-		case INT2OID:
 		case INT4OID:
-		case INT8OID:
-		case OIDOID:
-		case FLOAT4OID:
-		case FLOAT8OID:
+
+			/*
+			 * INT4 can be printed without any decoration, unless it is
+			 * negative; in that case print it as '-nnn'::integer to ensure
+			 * that the output will re-parse as a constant, not as a constant
+			 * plus operator.  In most cases we could get away with printing
+			 * (-nnn) instead, because of the way that gram.y handles negative
+			 * literals; but that doesn't work for INT_MIN, and it doesn't
+			 * seem that much prettier anyway.
+			 */
+			if (extval[0] != '-')
+				appendStringInfoString(buf, extval);
+			else
+			{
+				appendStringInfo(buf, "'%s'", extval);
+				needlabel = true;		/* we must attach a cast */
+			}
+			break;
+
 		case NUMERICOID:
+
+			/*
+			 * NUMERIC can be printed without quotes if it looks like a float
+			 * constant (not an integer, and not Infinity or NaN) and doesn't
+			 * have a leading sign (for the same reason as for INT4).
+			 */
+			if (isdigit((unsigned char) extval[0]) &&
+				strcspn(extval, "eE.") != strlen(extval))
 			{
-				/*
-				 * These types are printed without quotes unless they contain
-				 * values that aren't accepted by the scanner unquoted (e.g.,
-				 * 'NaN').  Note that strtod() and friends might accept NaN,
-				 * so we can't use that to test.
-				 *
-				 * In reality we only need to defend against infinity and NaN,
-				 * so we need not get too crazy about pattern matching here.
-				 *
-				 * There is a special-case gotcha: if the constant is signed,
-				 * we need to parenthesize it, else the parser might see a
-				 * leading plus/minus as binding less tightly than adjacent
-				 * operators --- particularly, the cast that we might attach
-				 * below.
-				 */
-				if (strspn(extval, "0123456789+-eE.") == strlen(extval))
-				{
-					if (extval[0] == '+' || extval[0] == '-')
-						appendStringInfo(buf, "(%s)", extval);
-					else
-						appendStringInfoString(buf, extval);
-					if (strcspn(extval, "eE.") != strlen(extval))
-						isfloat = true; /* it looks like a float */
-				}
-				else
-					appendStringInfo(buf, "'%s'", extval);
+				appendStringInfoString(buf, extval);
+			}
+			else
+			{
+				appendStringInfo(buf, "'%s'", extval);
+				needlabel = true;		/* we must attach a cast */
 			}
 			break;
 
@@ -8114,18 +8124,21 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
 	switch (constval->consttype)
 	{
 		case BOOLOID:
-		case INT4OID:
 		case UNKNOWNOID:
 			/* These types can be left unlabeled */
 			needlabel = false;
 			break;
+		case INT4OID:
+			/* We determined above whether a label is needed */
+			break;
 		case NUMERICOID:
 
 			/*
-			 * Float-looking constants will be typed as numeric, but if
-			 * there's a specific typmod we need to show it.
+			 * Float-looking constants will be typed as numeric, which we
+			 * checked above; but if there's a nondefault typmod we need to
+			 * show it.
 			 */
-			needlabel = !isfloat || (constval->consttypmod >= 0);
+			needlabel |= (constval->consttypmod >= 0);
 			break;
 		default:
 			needlabel = true;

src/test/regress/expected/equivclass.out

@@ -104,11 +104,11 @@ set enable_mergejoin = off;
 --
 explain (costs off)
   select * from ec0 where ff = f1 and f1 = '42'::int8;
-            QUERY PLAN            
-----------------------------------
+            QUERY PLAN             
+-----------------------------------
  Index Scan using ec0_pkey on ec0
-   Index Cond: (ff = 42::bigint)
-   Filter: (f1 = 42::bigint)
+   Index Cond: (ff = '42'::bigint)
+   Filter: (f1 = '42'::bigint)
 (3 rows)
 
 explain (costs off)
@@ -139,12 +139,12 @@ explain (costs off)
 
 explain (costs off)
   select * from ec1, ec2 where ff = x1 and ff = '42'::int8;
-                          QUERY PLAN                           
----------------------------------------------------------------
+                            QUERY PLAN                             
+-------------------------------------------------------------------
  Nested Loop
    Join Filter: (ec1.ff = ec2.x1)
    ->  Index Scan using ec1_pkey on ec1
-         Index Cond: ((ff = 42::bigint) AND (ff = 42::bigint))
+         Index Cond: ((ff = '42'::bigint) AND (ff = '42'::bigint))
    ->  Seq Scan on ec2
 (5 rows)
 
@@ -161,14 +161,14 @@ explain (costs off)
 
 explain (costs off)
   select * from ec1, ec2 where ff = x1 and '42'::int8 = x1;
-               QUERY PLAN               
-----------------------------------------
+               QUERY PLAN                
+-----------------------------------------
  Nested Loop
    Join Filter: (ec1.ff = ec2.x1)
    ->  Index Scan using ec1_pkey on ec1
-         Index Cond: (ff = 42::bigint)
+         Index Cond: (ff = '42'::bigint)
    ->  Seq Scan on ec2
-         Filter: (42::bigint = x1)
+         Filter: ('42'::bigint = x1)
 (6 rows)
 
 explain (costs off)
@@ -210,7 +210,7 @@ explain (costs off)
 -----------------------------------------------------
  Nested Loop
    ->  Index Scan using ec1_pkey on ec1
-         Index Cond: (ff = 42::bigint)
+         Index Cond: (ff = '42'::bigint)
    ->  Append
          ->  Index Scan using ec1_expr2 on ec1 ec1_1
                Index Cond: (((ff + 2) + 1) = ec1.f1)
@@ -229,20 +229,20 @@ explain (costs off)
      union all
      select ff + 4 as x from ec1) as ss1
   where ss1.x = ec1.f1 and ec1.ff = 42::int8 and ec1.ff = ec1.f1;
-                          QUERY PLAN                           
----------------------------------------------------------------
+                            QUERY PLAN                             
+-------------------------------------------------------------------
  Nested Loop
    Join Filter: ((((ec1_1.ff + 2) + 1)) = ec1.f1)
    ->  Index Scan using ec1_pkey on ec1
-         Index Cond: ((ff = 42::bigint) AND (ff = 42::bigint))
+         Index Cond: ((ff = '42'::bigint) AND (ff = '42'::bigint))
          Filter: (ff = f1)
    ->  Append
          ->  Index Scan using ec1_expr2 on ec1 ec1_1
-               Index Cond: (((ff + 2) + 1) = 42::bigint)
+               Index Cond: (((ff + 2) + 1) = '42'::bigint)
          ->  Index Scan using ec1_expr3 on ec1 ec1_2
-               Index Cond: (((ff + 3) + 1) = 42::bigint)
+               Index Cond: (((ff + 3) + 1) = '42'::bigint)
          ->  Index Scan using ec1_expr4 on ec1 ec1_3
-               Index Cond: ((ff + 4) = 42::bigint)
+               Index Cond: ((ff + 4) = '42'::bigint)
 (12 rows)
 
 explain (costs off)
@@ -265,7 +265,7 @@ explain (costs off)
  Nested Loop
    ->  Nested Loop
          ->  Index Scan using ec1_pkey on ec1
-               Index Cond: (ff = 42::bigint)
+               Index Cond: (ff = '42'::bigint)
          ->  Append
                ->  Index Scan using ec1_expr2 on ec1 ec1_1
                      Index Cond: (((ff + 2) + 1) = ec1.f1)
@@ -321,7 +321,7 @@ explain (costs off)
                      ->  Sort
                            Sort Key: ec1.f1 USING <
                            ->  Index Scan using ec1_pkey on ec1
-                                 Index Cond: (ff = 42::bigint)
+                                 Index Cond: (ff = '42'::bigint)
 (20 rows)
 
 -- check partially indexed scan
@@ -341,7 +341,7 @@ explain (costs off)
 -----------------------------------------------------
  Nested Loop
    ->  Index Scan using ec1_pkey on ec1
-         Index Cond: (ff = 42::bigint)
+         Index Cond: (ff = '42'::bigint)
    ->  Append
          ->  Index Scan using ec1_expr2 on ec1 ec1_1
                Index Cond: (((ff + 2) + 1) = ec1.f1)
@@ -378,6 +378,6 @@ explain (costs off)
          ->  Sort
                Sort Key: ec1.f1 USING <
                ->  Index Scan using ec1_pkey on ec1
-                     Index Cond: (ff = 42::bigint)
+                     Index Cond: (ff = '42'::bigint)
 (14 rows)