Represent BETWEEN as a special node type in raw parse trees.

Previously, gram.y itself converted BETWEEN into AND (or AND/OR) nests of
expression comparisons.  This was always as bogus as could be, but fixing
it hasn't risen to the top of the to-do list.  The present patch invents an
A_Expr representation for BETWEEN expressions, and does the expansion to
comparison trees in parse_expr.c which is at least a slightly saner place
to be doing semantic conversions.  There should be no change in the post-
parse-analysis results.

This does nothing for the semantic issues with BETWEEN (dubious connection
to btree-opclass semantics, and multiple evaluation of possibly volatile
subexpressions) ... but it's a necessary preliminary step before we could
fix any of that.  The main immediate benefit is that preserving BETWEEN as
an identifiable raw-parse-tree construct will enable better error messages.

While at it, fix the code so that multiply-referenced subexpressions are
physically duplicated before being passed through transformExpr().  This
gets rid of one of the principal reasons why transformExpr() has
historically had to allow already-processed input.

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 84864480624129fb4c3a8e05c9c435ace8960e73..d8e2077d6050f76880ca209d994003b091478479 100644 (file)
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2512,6 +2512,22 @@ _outAExpr(StringInfo str, const A_Expr *node)
            appendStringInfoString(str, " IN ");
            WRITE_NODE_FIELD(name);
            break;
+       case AEXPR_BETWEEN:
+           appendStringInfoString(str, " BETWEEN ");
+           WRITE_NODE_FIELD(name);
+           break;
+       case AEXPR_NOT_BETWEEN:
+           appendStringInfoString(str, " NOT_BETWEEN ");
+           WRITE_NODE_FIELD(name);
+           break;
+       case AEXPR_BETWEEN_SYM:
+           appendStringInfoString(str, " BETWEEN_SYM ");
+           WRITE_NODE_FIELD(name);
+           break;
+       case AEXPR_NOT_BETWEEN_SYM:
+           appendStringInfoString(str, " NOT_BETWEEN_SYM ");
+           WRITE_NODE_FIELD(name);
+           break;
        default:
            appendStringInfoString(str, " ??");
            break;

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 36dac299144ba8425d42730bae9076814fb164d7..67c7c84deecb4ab05a4f7facb91df32f1ff39c17 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11178,7 +11178,7 @@ a_expr:     c_expr                                  { $$ = $1; }
         * below; and all those operators will have the same precedence.
         *
         * If you add more explicitly-known operators, be sure to add them
-        * also to b_expr and to the MathOp list above.
+        * also to b_expr and to the MathOp list below.
         */
            | '+' a_expr                    %prec UMINUS
                { $$ = (Node *) makeSimpleA_Expr(AEXPR_OP, "+", NULL, $2, @1); }
@@ -11396,51 +11396,37 @@ a_expr:       c_expr                                  { $$ = $1; }
                {
                    $$ = (Node *) makeSimpleA_Expr(AEXPR_OF, "<>", $1, (Node *) $6, @2);
                }
-           /*
-            *  Ideally we would not use hard-wired operators below but
-            *  instead use opclasses.  However, mixed data types and other
-            *  issues make this difficult:
-            *  http://archives.postgresql.org/pgsql-hackers/2008-08/msg01142.php
-            */
            | a_expr BETWEEN opt_asymmetric b_expr AND b_expr       %prec BETWEEN
                {
-                   $$ = makeAndExpr(
-                       (Node *) makeSimpleA_Expr(AEXPR_OP, ">=", $1, $4, @2),
-                       (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $6, @2),
-                                    @2);
+                   $$ = (Node *) makeSimpleA_Expr(AEXPR_BETWEEN,
+                                                  "BETWEEN",
+                                                  $1,
+                                                  (Node *) list_make2($4, $6),
+                                                  @2);
                }
            | a_expr NOT BETWEEN opt_asymmetric b_expr AND b_expr   %prec BETWEEN
                {
-                   $$ = makeOrExpr(
-                       (Node *) makeSimpleA_Expr(AEXPR_OP, "<", $1, $5, @2),
-                       (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $7, @2),
-                                   @2);
+                   $$ = (Node *) makeSimpleA_Expr(AEXPR_NOT_BETWEEN,
+                                                  "NOT BETWEEN",
+                                                  $1,
+                                                  (Node *) list_make2($5, $7),
+                                                  @2);
                }
            | a_expr BETWEEN SYMMETRIC b_expr AND b_expr            %prec BETWEEN
                {
-                   $$ = makeOrExpr(
-                         makeAndExpr(
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, ">=", $1, $4, @2),
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $6, @2),
-                                     @2),
-                         makeAndExpr(
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, ">=", $1, $6, @2),
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, "<=", $1, $4, @2),
-                                     @2),
-                                   @2);
+                   $$ = (Node *) makeSimpleA_Expr(AEXPR_BETWEEN_SYM,
+                                                  "BETWEEN SYMMETRIC",
+                                                  $1,
+                                                  (Node *) list_make2($4, $6),
+                                                  @2);
                }
            | a_expr NOT BETWEEN SYMMETRIC b_expr AND b_expr        %prec BETWEEN
                {
-                   $$ = makeAndExpr(
-                          makeOrExpr(
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, "<", $1, $5, @2),
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $7, @2),
-                                     @2),
-                          makeOrExpr(
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, "<", $1, $7, @2),
-                           (Node *) makeSimpleA_Expr(AEXPR_OP, ">", $1, $5, @2),
-                                     @2),
-                                    @2);
+                   $$ = (Node *) makeSimpleA_Expr(AEXPR_NOT_BETWEEN_SYM,
+                                                  "NOT BETWEEN SYMMETRIC",
+                                                  $1,
+                                                  (Node *) list_make2($5, $7),
+                                                  @2);
                }
            | a_expr IN_P in_expr
                {

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index f0f0488c57ad52691bb946e7de4c820a08054bb8..67a2310ad0e0e881f94a66cff90f34420700980a 100644 (file)
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -48,6 +48,7 @@ static Node *transformAExprDistinct(ParseState *pstate, A_Expr *a);
 static Node *transformAExprNullIf(ParseState *pstate, A_Expr *a);
 static Node *transformAExprOf(ParseState *pstate, A_Expr *a);
 static Node *transformAExprIn(ParseState *pstate, A_Expr *a);
+static Node *transformAExprBetween(ParseState *pstate, A_Expr *a);
 static Node *transformBoolExpr(ParseState *pstate, BoolExpr *a);
 static Node *transformFuncCall(ParseState *pstate, FuncCall *fn);
 static Node *transformMultiAssignRef(ParseState *pstate, MultiAssignRef *maref);
@@ -241,6 +242,12 @@ transformExprRecurse(ParseState *pstate, Node *expr)
                    case AEXPR_IN:
                        result = transformAExprIn(pstate, a);
                        break;
+                   case AEXPR_BETWEEN:
+                   case AEXPR_NOT_BETWEEN:
+                   case AEXPR_BETWEEN_SYM:
+                   case AEXPR_NOT_BETWEEN_SYM:
+                       result = transformAExprBetween(pstate, a);
+                       break;
                    default:
                        elog(ERROR, "unrecognized A_Expr kind: %d", a->kind);
                        result = NULL;  /* keep compiler quiet */
@@ -1195,6 +1202,101 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
    return result;
 }
 
+static Node *
+transformAExprBetween(ParseState *pstate, A_Expr *a)
+{
+   Node       *aexpr;
+   Node       *bexpr;
+   Node       *cexpr;
+   Node       *result;
+   Node       *sub1;
+   Node       *sub2;
+   List       *args;
+
+   /* Deconstruct A_Expr into three subexprs */
+   aexpr = a->lexpr;
+   Assert(IsA(a->rexpr, List));
+   args = (List *) a->rexpr;
+   Assert(list_length(args) == 2);
+   bexpr = (Node *) linitial(args);
+   cexpr = (Node *) lsecond(args);
+
+   /*
+    * Build the equivalent comparison expression.  Make copies of
+    * multiply-referenced subexpressions for safety.  (XXX this is really
+    * wrong since it results in multiple runtime evaluations of what may be
+    * volatile expressions ...)
+    *
+    * Ideally we would not use hard-wired operators here but instead use
+    * opclasses.  However, mixed data types and other issues make this
+    * difficult:
+    * http://archives.postgresql.org/pgsql-hackers/2008-08/msg01142.php
+    */
+   switch (a->kind)
+   {
+       case AEXPR_BETWEEN:
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, ">=",
+                                              aexpr, bexpr,
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, "<=",
+                                              copyObject(aexpr), cexpr,
+                                              a->location));
+           result = (Node *) makeBoolExpr(AND_EXPR, args, a->location);
+           break;
+       case AEXPR_NOT_BETWEEN:
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, "<",
+                                              aexpr, bexpr,
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, ">",
+                                              copyObject(aexpr), cexpr,
+                                              a->location));
+           result = (Node *) makeBoolExpr(OR_EXPR, args, a->location);
+           break;
+       case AEXPR_BETWEEN_SYM:
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, ">=",
+                                              aexpr, bexpr,
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, "<=",
+                                              copyObject(aexpr), cexpr,
+                                              a->location));
+           sub1 = (Node *) makeBoolExpr(AND_EXPR, args, a->location);
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, ">=",
+                                       copyObject(aexpr), copyObject(cexpr),
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, "<=",
+                                       copyObject(aexpr), copyObject(bexpr),
+                                              a->location));
+           sub2 = (Node *) makeBoolExpr(AND_EXPR, args, a->location);
+           args = list_make2(sub1, sub2);
+           result = (Node *) makeBoolExpr(OR_EXPR, args, a->location);
+           break;
+       case AEXPR_NOT_BETWEEN_SYM:
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, "<",
+                                              aexpr, bexpr,
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, ">",
+                                              copyObject(aexpr), cexpr,
+                                              a->location));
+           sub1 = (Node *) makeBoolExpr(OR_EXPR, args, a->location);
+           args = list_make2(makeSimpleA_Expr(AEXPR_OP, "<",
+                                       copyObject(aexpr), copyObject(cexpr),
+                                              a->location),
+                             makeSimpleA_Expr(AEXPR_OP, ">",
+                                       copyObject(aexpr), copyObject(bexpr),
+                                              a->location));
+           sub2 = (Node *) makeBoolExpr(OR_EXPR, args, a->location);
+           args = list_make2(sub1, sub2);
+           result = (Node *) makeBoolExpr(AND_EXPR, args, a->location);
+           break;
+       default:
+           elog(ERROR, "unrecognized A_Expr kind: %d", a->kind);
+           result = NULL;      /* keep compiler quiet */
+           break;
+   }
+
+   return transformExprRecurse(pstate, result);
+}
+
 static Node *
 transformBoolExpr(ParseState *pstate, BoolExpr *a)
 {

diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85eb0d703bed9fb633270bdfc21d8739182..35b68ec033252e8a76666fae68efd48fdbd9dda5 100644 (file)
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -232,7 +232,11 @@ typedef enum A_Expr_Kind
    AEXPR_DISTINCT,             /* IS DISTINCT FROM - name must be "=" */
    AEXPR_NULLIF,               /* NULLIF - name must be "=" */
    AEXPR_OF,                   /* IS [NOT] OF - name must be "=" or "<>" */
-   AEXPR_IN                    /* [NOT] IN - name must be "=" or "<>" */
+   AEXPR_IN,                   /* [NOT] IN - name must be "=" or "<>" */
+   AEXPR_BETWEEN,              /* name must be "BETWEEN" */
+   AEXPR_NOT_BETWEEN,          /* name must be "NOT BETWEEN" */
+   AEXPR_BETWEEN_SYM,          /* name must be "BETWEEN SYMMETRIC" */
+   AEXPR_NOT_BETWEEN_SYM       /* name must be "NOT BETWEEN SYMMETRIC" */
 } A_Expr_Kind;
 
 typedef struct A_Expr