Make the world at least somewhat safe for zero-column tables, and

remove the special case in ALTER DROP COLUMN to prohibit dropping a
table's last column.

diff --git a/src/backend/access/common/tupdesc.c b/src/backend/access/common/tupdesc.c
index 5a1b912b3796b5ca96343ea4061a712fe725705e..f1f92af4725398677d6d8a90586ef86a43e21114 100644 (file)
--- a/src/backend/access/common/tupdesc.c
+++ b/src/backend/access/common/tupdesc.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/access/common/tupdesc.c,v 1.90 2002/09/22 19:42:50 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/access/common/tupdesc.c,v 1.91 2002/09/28 20:00:18 tgl Exp $
  *
  * NOTES
  *   some of the executor utility code such as "ExecTypeFromTL" should be
@@ -39,28 +39,34 @@
 TupleDesc
 CreateTemplateTupleDesc(int natts, bool hasoid)
 {
-   uint32      size;
    TupleDesc   desc;
 
    /*
     * sanity checks
     */
-   AssertArg(natts >= 1);
+   AssertArg(natts >= 0);
 
    /*
     * allocate enough memory for the tuple descriptor and zero it as
     * TupleDescInitEntry assumes that the descriptor is filled with NULL
     * pointers.
     */
-   size = natts * sizeof(Form_pg_attribute);
    desc = (TupleDesc) palloc(sizeof(struct tupleDesc));
-   desc->attrs = (Form_pg_attribute *) palloc(size);
-   desc->constr = NULL;
-   MemSet(desc->attrs, 0, size);
 
    desc->natts = natts;
    desc->tdhasoid = hasoid;
 
+   if (natts > 0)
+   {
+       uint32      size = natts * sizeof(Form_pg_attribute);
+
+       desc->attrs = (Form_pg_attribute *) palloc(size);
+       MemSet(desc->attrs, 0, size);
+   }
+   else
+       desc->attrs = NULL;
+   desc->constr = NULL;
+
    return desc;
 }
 
@@ -79,7 +85,7 @@ CreateTupleDesc(int natts, bool hasoid, Form_pg_attribute *attrs)
    /*
     * sanity checks
     */
-   AssertArg(natts >= 1);
+   AssertArg(natts >= 0);
 
    desc = (TupleDesc) palloc(sizeof(struct tupleDesc));
    desc->attrs = attrs;
@@ -108,17 +114,20 @@ CreateTupleDescCopy(TupleDesc tupdesc)
 
    desc = (TupleDesc) palloc(sizeof(struct tupleDesc));
    desc->natts = tupdesc->natts;
-   size = desc->natts * sizeof(Form_pg_attribute);
-   desc->attrs = (Form_pg_attribute *) palloc(size);
-   for (i = 0; i < desc->natts; i++)
+   if (desc->natts > 0)
    {
-       desc->attrs[i] = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
-       memcpy(desc->attrs[i],
-              tupdesc->attrs[i],
-              ATTRIBUTE_TUPLE_SIZE);
-       desc->attrs[i]->attnotnull = false;
-       desc->attrs[i]->atthasdef = false;
+       size = desc->natts * sizeof(Form_pg_attribute);
+       desc->attrs = (Form_pg_attribute *) palloc(size);
+       for (i = 0; i < desc->natts; i++)
+       {
+           desc->attrs[i] = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
+           memcpy(desc->attrs[i], tupdesc->attrs[i], ATTRIBUTE_TUPLE_SIZE);
+           desc->attrs[i]->attnotnull = false;
+           desc->attrs[i]->atthasdef = false;
+       }
    }
+   else
+       desc->attrs = NULL;
    desc->constr = NULL;
    desc->tdhasoid = tupdesc->tdhasoid;
 
@@ -142,15 +151,18 @@ CreateTupleDescCopyConstr(TupleDesc tupdesc)
 
    desc = (TupleDesc) palloc(sizeof(struct tupleDesc));
    desc->natts = tupdesc->natts;
-   size = desc->natts * sizeof(Form_pg_attribute);
-   desc->attrs = (Form_pg_attribute *) palloc(size);
-   for (i = 0; i < desc->natts; i++)
+   if (desc->natts > 0)
    {
-       desc->attrs[i] = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
-       memcpy(desc->attrs[i],
-              tupdesc->attrs[i],
-              ATTRIBUTE_TUPLE_SIZE);
+       size = desc->natts * sizeof(Form_pg_attribute);
+       desc->attrs = (Form_pg_attribute *) palloc(size);
+       for (i = 0; i < desc->natts; i++)
+       {
+           desc->attrs[i] = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
+           memcpy(desc->attrs[i], tupdesc->attrs[i], ATTRIBUTE_TUPLE_SIZE);
+       }
    }
+   else
+       desc->attrs = NULL;
    if (constr)
    {
        TupleConstr *cpy = (TupleConstr *) palloc(sizeof(TupleConstr));
@@ -197,7 +209,8 @@ FreeTupleDesc(TupleDesc tupdesc)
 
    for (i = 0; i < tupdesc->natts; i++)
        pfree(tupdesc->attrs[i]);
-   pfree(tupdesc->attrs);
+   if (tupdesc->attrs)
+       pfree(tupdesc->attrs);
    if (tupdesc->constr)
    {
        if (tupdesc->constr->num_defval > 0)
@@ -228,7 +241,6 @@ FreeTupleDesc(TupleDesc tupdesc)
    }
 
    pfree(tupdesc);
-
 }
 
 /*
@@ -361,6 +373,7 @@ TupleDescInitEntry(TupleDesc desc,
     */
    AssertArg(PointerIsValid(desc));
    AssertArg(attributeNumber >= 1);
+   AssertArg(attributeNumber <= desc->natts);
 
    /*
     * attributeName's are sometimes NULL, from resdom's.  I don't know

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 0934a274c7ad3d76d8707ac48af1b0fea0a84111..14d82630c8adeed544e216fa829995a318d1d1ca 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.44 2002/09/23 20:43:40 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.45 2002/09/28 20:00:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2331,9 +2331,7 @@ AlterTableDropColumn(Oid myrelid, bool recurse, bool recursing,
 {
    Relation    rel;
    AttrNumber  attnum;
-   AttrNumber  n;
    TupleDesc   tupleDesc;
-   bool        success;
    ObjectAddress object;
 
    rel = heap_open(myrelid, AccessExclusiveLock);
@@ -2359,34 +2357,13 @@ AlterTableDropColumn(Oid myrelid, bool recurse, bool recursing,
             RelationGetRelationName(rel), colName);
 
    /* Can't drop a system attribute */
+   /* XXX perhaps someday allow dropping OID? */
    if (attnum < 0)
        elog(ERROR, "ALTER TABLE: Cannot drop system attribute \"%s\"",
             colName);
 
-   /*
-    * Make sure there will be at least one user column left in the
-    * relation after we drop this one.  Zero-length tuples tend to
-    * confuse us.
-    */
-   tupleDesc = RelationGetDescr(rel);
-
-   success = false;
-   for (n = 1; n <= tupleDesc->natts; n++)
-   {
-       Form_pg_attribute attribute = tupleDesc->attrs[n - 1];
-
-       if (!attribute->attisdropped && n != attnum)
-       {
-           success = true;
-           break;
-       }
-   }
-
-   if (!success)
-       elog(ERROR, "ALTER TABLE: Cannot drop last column from table \"%s\"",
-            RelationGetRelationName(rel));
-
    /* Don't drop inherited columns */
+   tupleDesc = RelationGetDescr(rel);
    if (tupleDesc->attrs[attnum - 1]->attinhcount > 0 && !recursing)
        elog(ERROR, "ALTER TABLE: Cannot drop inherited column \"%s\"",
             colName);

diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
index 1a5f835be1dd3d8a0b3a231c6a6fca6d0f1c0493..7b0df664c7468ed6b9f32f5535baddf443d82231 100644 (file)
--- a/src/backend/executor/execTuples.c
+++ b/src/backend/executor/execTuples.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/executor/execTuples.c,v 1.59 2002/09/04 20:31:17 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/executor/execTuples.c,v 1.60 2002/09/28 20:00:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -560,23 +560,14 @@ ExecInitNullTupleSlot(EState *estate, TupleDesc tupType)
 TupleDesc
 ExecTypeFromTL(List *targetList, bool hasoid)
 {
-   List       *tlitem;
    TupleDesc   typeInfo;
-   Resdom     *resdom;
-   Oid         restype;
+   List       *tlitem;
    int         len;
 
-   /*
-    * examine targetlist - if empty then return NULL
-    */
-   len = ExecTargetListLength(targetList);
-
-   if (len == 0)
-       return NULL;
-
    /*
     * allocate a new typeInfo
     */
+   len = ExecTargetListLength(targetList);
    typeInfo = CreateTemplateTupleDesc(len, hasoid);
 
    /*
@@ -585,6 +576,8 @@ ExecTypeFromTL(List *targetList, bool hasoid)
    foreach(tlitem, targetList)
    {
        TargetEntry *tle = lfirst(tlitem);
+       Resdom     *resdom;
+       Oid         restype;
 
        if (tle->resdom != NULL)
        {

diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index 898ca62a6005495b8c0e438e5f2332fa667762ab..0ebf2f7151e5050a4e49c164df14fa7e8151f3c6 100644 (file)
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -46,7 +46,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.87 2002/09/18 21:35:20 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/executor/nodeAgg.c,v 1.88 2002/09/28 20:00:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -658,20 +658,20 @@ ExecAgg(Agg *node)
            if (inputTuple == NULL)
            {
                TupleDesc   tupType;
-               Datum      *tupValue;
-               char       *null_array;
-               AttrNumber  attnum;
+               Datum      *dvalues;
+               char       *dnulls;
 
                tupType = aggstate->csstate.css_ScanTupleSlot->ttc_tupleDescriptor;
-               tupValue = projInfo->pi_tupValue;
                /* watch out for null input tuples, though... */
-               if (tupType && tupValue)
+               if (tupType && tupType->natts > 0)
                {
-                   null_array = (char *) palloc(sizeof(char) * tupType->natts);
-                   for (attnum = 0; attnum < tupType->natts; attnum++)
-                       null_array[attnum] = 'n';
-                   inputTuple = heap_formtuple(tupType, tupValue, null_array);
-                   pfree(null_array);
+                   dvalues = (Datum *) palloc(sizeof(Datum) * tupType->natts);
+                   dnulls = (char *) palloc(sizeof(char) * tupType->natts);
+                   MemSet(dvalues, 0, sizeof(Datum) * tupType->natts);
+                   MemSet(dnulls, 'n', sizeof(char) * tupType->natts);
+                   inputTuple = heap_formtuple(tupType, dvalues, dnulls);
+                   pfree(dvalues);
+                   pfree(dnulls);
                }
            }
        }

diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 18d11cc7f5ac55c5f0ba87eab9a63f66389b66ce..c03db4f8b4b36fbf65e84a1c2190be0a3a1bb74c 100644 (file)
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.90 2002/09/18 21:35:22 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.91 2002/09/28 20:00:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -386,6 +386,7 @@ static List *
 ExpandAllTables(ParseState *pstate)
 {
    List       *target = NIL;
+   bool        found_table = false;
    List       *ns;
 
    foreach(ns, pstate->p_namespace)
@@ -413,11 +414,12 @@ ExpandAllTables(ParseState *pstate)
        if (!rte->inFromCl)
            continue;
 
+       found_table = true;
        target = nconc(target, expandRelAttrs(pstate, rte));
    }
 
    /* Check for SELECT *; */
-   if (target == NIL)
+   if (!found_table)
        elog(ERROR, "Wildcard with no tables specified not allowed");
 
    return target;

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index de2e4a29757b7b5a4658bc548f9663094d963b49..f604c1c0dd0ddac5dc29f882e7911d1763c81a46 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -939,11 +939,9 @@ drop table test2;
 alter table atacc1 drop c;
 alter table atacc1 drop d;
 alter table atacc1 drop b;
-ERROR:  ALTER TABLE: Cannot drop last column from table "atacc1"
 select * from atacc1;
- b  
-----
- 21
+  
+--
 (1 row)
 
 drop table atacc1;