Remove the hack in the grammar that "optimized away" DEFAULT NULL clauses.

Instead put in a test to drop a NULL default at the last moment before
storing the catalog entry.  This changes the behavior in a couple of ways:
* Specifying DEFAULT NULL when creating an inheritance child table will
  successfully suppress inheritance of any default expression from the
  parent's column, where formerly it failed to do so.
* Specifying DEFAULT NULL for a column of a domain type will correctly
  override any default belonging to the domain; likewise for a sub-domain.
The latter change happens because by the time the clause is checked,
it won't be a simple null Const but a CoerceToDomain expression.

Personally I think this should be back-patched, but there doesn't seem to
be consensus for that on pgsql-hackers, so refraining.

diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index a744afc51f436ed573ac32ac30866db659c5e99a..210442012a7c0f34116cdd36e7956a83bb8133fa 100644 (file)
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -1722,6 +1722,21 @@ AddRelationRawConstraints(Relation rel,
                                                   atp->atttypid, atp->atttypmod,
                                                   NameStr(atp->attname));
 
+               /*
+                * If the expression is just a NULL constant, we do not bother
+                * to make an explicit pg_attrdef entry, since the default behavior
+                * is equivalent.
+                *
+                * Note a nonobvious property of this test: if the column is of a
+                * domain type, what we'll get is not a bare null Const but a
+                * CoerceToDomain expr, so we will not discard the default.  This is
+                * critical because the column default needs to be retained to
+                * override any default that the domain might have.
+                */
+               if (expr == NULL ||
+                       (IsA(expr, Const) && ((Const *) expr)->constisnull))
+                       continue;
+
                StoreAttrDefault(rel, colDef->attnum, nodeToString(expr));
 
                cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));

diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index ab24a39cf234321a98ff4d3f78d24bc5925b6e07..11ae6f4b8b31efd159c5fe4e8914c1ad586b1c0d 100644 (file)
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -765,20 +765,40 @@ DefineDomain(CreateDomainStmt *stmt)
                                                                                          domainName);
 
                                        /*
-                                        * Expression must be stored as a nodeToString result, but
-                                        * we also require a valid textual representation (mainly
-                                        * to make life easier for pg_dump).
+                                        * If the expression is just a NULL constant, we treat
+                                        * it like not having a default.
+                                        *
+                                        * Note that if the basetype is another domain, we'll see
+                                        * a CoerceToDomain expr here and not discard the default.
+                                        * This is critical because the domain default needs to be
+                                        * retained to override any default that the base domain
+                                        * might have.
                                         */
-                                       defaultValue =
-                                               deparse_expression(defaultExpr,
-                                                                                  deparse_context_for(domainName,
-                                                                                                                          InvalidOid),
-                                                                                  false, false);
-                                       defaultValueBin = nodeToString(defaultExpr);
+                                       if (defaultExpr == NULL ||
+                                               (IsA(defaultExpr, Const) &&
+                                                ((Const *) defaultExpr)->constisnull))
+                                       {
+                                               defaultValue = NULL;
+                                               defaultValueBin = NULL;
+                                       }
+                                       else
+                                       {
+                                               /*
+                                                * Expression must be stored as a nodeToString result,
+                                                * but we also require a valid textual representation
+                                                * (mainly to make life easier for pg_dump).
+                                                */
+                                               defaultValue =
+                                                       deparse_expression(defaultExpr,
+                                                                                          deparse_context_for(domainName,
+                                                                                                                                  InvalidOid),
+                                                                                          false, false);
+                                               defaultValueBin = nodeToString(defaultExpr);
+                                       }
                                }
                                else
                                {
-                                       /* DEFAULT NULL is same as not having a default */
+                                       /* No default (can this still happen?) */
                                        defaultValue = NULL;
                                        defaultValueBin = NULL;
                                }
@@ -1443,7 +1463,7 @@ AlterDomainDefault(List *names, Node *defaultRaw)
        MemSet(new_record_nulls, ' ', sizeof(new_record_nulls));
        MemSet(new_record_repl, ' ', sizeof(new_record_repl));
 
-       /* Store the new default, if null then skip this step */
+       /* Store the new default into the tuple */
        if (defaultRaw)
        {
                /* Create a dummy ParseState for transformExpr */
@@ -1459,30 +1479,46 @@ AlterDomainDefault(List *names, Node *defaultRaw)
                                                                  NameStr(typTup->typname));
 
                /*
-                * Expression must be stored as a nodeToString result, but we also
-                * require a valid textual representation (mainly to make life easier
-                * for pg_dump).
+                * If the expression is just a NULL constant, we treat the command
+                * like ALTER ... DROP DEFAULT.  (But see note for same test in
+                * DefineDomain.)
                 */
-               defaultValue = deparse_expression(defaultExpr,
+               if (defaultExpr == NULL ||
+                       (IsA(defaultExpr, Const) && ((Const *) defaultExpr)->constisnull))
+               {
+                       /* Default is NULL, drop it */
+                       new_record_nulls[Anum_pg_type_typdefaultbin - 1] = 'n';
+                       new_record_repl[Anum_pg_type_typdefaultbin - 1] = 'r';
+                       new_record_nulls[Anum_pg_type_typdefault - 1] = 'n';
+                       new_record_repl[Anum_pg_type_typdefault - 1] = 'r';
+               }
+               else
+               {
+                       /*
+                        * Expression must be stored as a nodeToString result, but we also
+                        * require a valid textual representation (mainly to make life
+                        * easier for pg_dump).
+                        */
+                       defaultValue = deparse_expression(defaultExpr,
                                                                deparse_context_for(NameStr(typTup->typname),
                                                                                                        InvalidOid),
                                                                                  false, false);
 
-               /*
-                * Form an updated tuple with the new default and write it back.
-                */
-               new_record[Anum_pg_type_typdefaultbin - 1] = DirectFunctionCall1(textin,
-                                                                                                                        CStringGetDatum(
-                                                                                                nodeToString(defaultExpr)));
+                       /*
+                        * Form an updated tuple with the new default and write it back.
+                        */
+                       new_record[Anum_pg_type_typdefaultbin - 1] = DirectFunctionCall1(textin,
+                                                               CStringGetDatum(nodeToString(defaultExpr)));
 
-               new_record_repl[Anum_pg_type_typdefaultbin - 1] = 'r';
-               new_record[Anum_pg_type_typdefault - 1] = DirectFunctionCall1(textin,
+                       new_record_repl[Anum_pg_type_typdefaultbin - 1] = 'r';
+                       new_record[Anum_pg_type_typdefault - 1] = DirectFunctionCall1(textin,
                                                                                          CStringGetDatum(defaultValue));
-               new_record_repl[Anum_pg_type_typdefault - 1] = 'r';
+                       new_record_repl[Anum_pg_type_typdefault - 1] = 'r';
+               }
        }
        else
-               /* Default is NULL, drop it */
        {
+               /* ALTER ... DROP DEFAULT */
                new_record_nulls[Anum_pg_type_typdefaultbin - 1] = 'n';
                new_record_repl[Anum_pg_type_typdefaultbin - 1] = 'r';
                new_record_nulls[Anum_pg_type_typdefault - 1] = 'n';

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 6ded56db4c96a9cef03b6023aafd03829760086d..4028e05af781568588e303d511babe5b818994d4 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -1685,14 +1685,7 @@ alter_rel_cmd:
                ;
 
 alter_column_default:
-                       SET DEFAULT a_expr
-                               {
-                                       /* Treat SET DEFAULT NULL the same as DROP DEFAULT */
-                                       if (exprIsNullConstant($3))
-                                               $$ = NULL;
-                                       else
-                                               $$ = $3;
-                               }
+                       SET DEFAULT a_expr                      { $$ = $3; }
                        | DROP DEFAULT                          { $$ = NULL; }
                ;
 
@@ -2080,15 +2073,7 @@ ColConstraintElem:
                                        Constraint *n = makeNode(Constraint);
                                        n->contype = CONSTR_DEFAULT;
                                        n->name = NULL;
-                                       if (exprIsNullConstant($2))
-                                       {
-                                               /* DEFAULT NULL should be reported as empty expr */
-                                               n->raw_expr = NULL;
-                                       }
-                                       else
-                                       {
-                                               n->raw_expr = $2;
-                                       }
+                                       n->raw_expr = $2;
                                        n->cooked_expr = NULL;
                                        n->keys = NULL;
                                        n->indexspace = NULL;
@@ -9763,23 +9748,6 @@ parser_init(void)
        QueryIsRule = FALSE;
 }
 
-/* exprIsNullConstant()
- * Test whether an a_expr is a plain NULL constant or not.
- */
-bool
-exprIsNullConstant(Node *arg)
-{
-       if (arg && IsA(arg, A_Const))
-       {
-               A_Const *con = (A_Const *) arg;
-
-               if (con->val.type == T_Null &&
-                       con->typename == NULL)
-                       return TRUE;
-       }
-       return FALSE;
-}
-
 /* doNegate()
  * Handle negation of a numeric constant.
  *

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 76691103d992b75c83d2617ee1c9cac5c553f20f..7818456b5158a048ae11a016c7a7a47790e1742b 100644 (file)
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -606,6 +606,21 @@ transformParamRef(ParseState *pstate, ParamRef *pref)
        return (Node *) param;
 }
 
+/* Test whether an a_expr is a plain NULL constant or not */
+static bool
+exprIsNullConstant(Node *arg)
+{
+       if (arg && IsA(arg, A_Const))
+       {
+               A_Const *con = (A_Const *) arg;
+
+               if (con->val.type == T_Null &&
+                       con->typename == NULL)
+                       return true;
+       }
+       return false;
+}
+
 static Node *
 transformAExprOp(ParseState *pstate, A_Expr *a)
 {

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 45583d97dc3c1c6eb75f70bc90aa8fa5c62bb203..af6451b4f38427b1e523aa485964f1188617a0e8 100644 (file)
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -440,7 +440,6 @@ transformColumnDefinition(ParseState *pstate, CreateStmtContext *cxt,
                                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                                         errmsg("multiple default values specified for column \"%s\" of table \"%s\"",
                                                                  column->colname, cxt->relation->relname)));
-                               /* Note: DEFAULT NULL maps to constraint->raw_expr == NULL */
                                column->raw_default = constraint->raw_expr;
                                Assert(constraint->cooked_expr == NULL);
                                saw_default = true;

diff --git a/src/include/parser/gramparse.h b/src/include/parser/gramparse.h
index 621f0b7cabcfd5bdf5586ff46db01da378ba9388..46ac116d1f8273d14e7a9f2ca19a0eedb7c7384f 100644 (file)
--- a/src/include/parser/gramparse.h
+++ b/src/include/parser/gramparse.h
@@ -54,6 +54,5 @@ extern void parser_init(void);
 extern int     base_yyparse(void);
 extern List *SystemFuncName(char *name);
 extern TypeName *SystemTypeName(char *name);
-extern bool exprIsNullConstant(Node *arg);
 
 #endif   /* GRAMPARSE_H */

diff --git a/src/test/regress/expected/domain.out b/src/test/regress/expected/domain.out
index c7d5b50334537ccd1db499bb75b4d3b0eb1a1e6d..b951ce8caa8752e36a0e52a38437ad590267aaa1 100644 (file)
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -205,7 +205,15 @@ create table defaulttest
             , col8 ddef5
             );
 NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "defaulttest_pkey" for table "defaulttest"
-insert into defaulttest default values;
+insert into defaulttest(col4) values(0); -- fails, col5 defaults to null
+ERROR:  null value in column "col5" violates not-null constraint
+alter table defaulttest alter column col5 drop default;
+insert into defaulttest default values; -- succeeds, inserts domain default
+-- We used to treat SET DEFAULT NULL as equivalent to DROP DEFAULT; wrong
+alter table defaulttest alter column col5 set default null;
+insert into defaulttest(col4) values(0); -- fails
+ERROR:  null value in column "col5" violates not-null constraint
+alter table defaulttest alter column col5 drop default;
 insert into defaulttest default values;
 insert into defaulttest default values;
 -- Test defaults with copy

diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index 7da99719911348c134f4fe58c73e711d0f896da6..7a4ec383d20cac750f67d0dc54c3eb22cb7ae782 100644 (file)
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -168,7 +168,13 @@ create table defaulttest
             , col7 ddef4 DEFAULT 8000
             , col8 ddef5
             );
-insert into defaulttest default values;
+insert into defaulttest(col4) values(0); -- fails, col5 defaults to null
+alter table defaulttest alter column col5 drop default;
+insert into defaulttest default values; -- succeeds, inserts domain default
+-- We used to treat SET DEFAULT NULL as equivalent to DROP DEFAULT; wrong
+alter table defaulttest alter column col5 set default null;
+insert into defaulttest(col4) values(0); -- fails
+alter table defaulttest alter column col5 drop default;
 insert into defaulttest default values;
 insert into defaulttest default values;