> Sure send it in, we can put it in contrib. > > > > > I wrote a

real small function to revoke update on a column. The function >
> doesn't do anything > > fancy like checking user ids.  > > > >
I copied most of it from the refint.c in the contrib directory.
> > > > Should I post this somewhere? It really isn't very big.
> >

Here it is...

--
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Rick Poleshuck  | Voice - (908) 653-1070      Fax - (908) 653-0265
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diff --git a/contrib/noupdate/noup.c b/contrib/noupdate/noup.c
new file mode 100644 (file)
index 0000000..efbe031
--- /dev/null
+++ b/contrib/noupdate/noup.c
@@ -0,0 +1,111 @@
+/*
+ * noup.c --   functions to remove update permission from a column
+ */
+
+#include "executor/spi.h"              /* this is what you need to work with SPI */
+#include "commands/trigger.h"  /* -"- and triggers */
+#include <ctype.h>                             /* tolower () */
+
+HeapTuple      noup(void);
+
+/*
+ * noup () -- revoke permission on column
+ *
+ * Though it's called without args You have to specify referenced
+ * table/column while creating trigger:  
+ * EXECUTE PROCEDURE noup ('col').
+ */
+
+HeapTuple                                              /* have to return HeapTuple to Executor */
+noup()
+{
+       Trigger    *trigger;            /* to get trigger name */
+       int                     nargs;                  /* # of args specified in CREATE TRIGGER */
+       char      **args;                       /* arguments: column names and table name */
+       int                     nkeys;                  /* # of key columns (= nargs / 2) */
+       Datum      *kvals;                      /* key values */
+       Relation        rel;                    /* triggered relation */
+       HeapTuple       tuple = NULL;   /* tuple to return */
+       TupleDesc       tupdesc;                /* tuple description */
+       bool            isnull;                 /* to know is some column NULL or not */
+       int                     ret;
+       int                     i;
+
+       /*
+        * Some checks first...
+        */
+
+       /* Called by trigger manager ? */
+       if (!CurrentTriggerData)
+               elog(WARN, "noup: triggers are not initialized");
+
+       /* Should be called for ROW trigger */
+       if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+               elog(WARN, "noup: can't process STATEMENT events");
+
+       /* Not should be called for INSERT */
+       if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
+               elog(WARN, "noup: can't process INSERT events");
+
+       /* Not should be called for DELETE */
+       else if (TRIGGER_FIRED_BY_DELETE(CurrentTriggerData->tg_event))
+               elog(WARN, "noup: can't process DELETE events");
+
+       /* check new Tuple */
+       tuple = CurrentTriggerData->tg_newtuple;
+
+       trigger = CurrentTriggerData->tg_trigger;
+       nargs = trigger->tgnargs;
+       args = trigger->tgargs;
+
+       nkeys = nargs;
+       rel = CurrentTriggerData->tg_relation;
+       tupdesc = rel->rd_att;
+
+       /*
+        * Setting CurrentTriggerData to NULL prevents direct calls to trigger
+        * functions in queries. Normally, trigger functions have to be called
+        * by trigger manager code only.
+        */
+       CurrentTriggerData = NULL;
+
+       /* Connect to SPI manager */
+       if ((ret = SPI_connect()) < 0)
+               elog(WARN, "noup: SPI_connect returned %d", ret);
+
+       /*
+        * We use SPI plan preparation feature, so allocate space to place key
+        * values.
+        */
+       kvals = (Datum *) palloc(nkeys * sizeof(Datum));
+
+       /* For each column in key ... */
+       for (i = 0; i < nkeys; i++)
+       {
+               /* get index of column in tuple */
+               int                     fnumber = SPI_fnumber(tupdesc, args[i]);
+
+               /* Bad guys may give us un-existing column in CREATE TRIGGER */
+               if (fnumber < 0)
+                       elog(WARN, "noup: there is no attribute %s in relation %s",
+                                args[i], SPI_getrelname(rel));
+
+               /* Well, get binary (in internal format) value of column */
+               kvals[i] = SPI_getbinval(tuple, tupdesc, fnumber, &isnull);
+
+               /*
+                * If it's NOT NULL then cancel update
+                */
+               if (!isnull)
+               {
+       
+                       elog(WARN, "%s: update not allowed", args[i] );
+                       SPI_finish();
+                       return NULL;
+               }
+
+       }
+
+       SPI_finish();
+       return (tuple);
+}

diff --git a/contrib/noupdate/noup.example b/contrib/noupdate/noup.example
new file mode 100644 (file)
index 0000000..62db1ee
--- /dev/null
+++ b/contrib/noupdate/noup.example
@@ -0,0 +1,9 @@
+CREATE TABLE TEST ( COL1 INT, COL2 INT, COL3 INT );
+
+CREATE TRIGGER BT BEFORE UPDATE ON TEST FOR EACH ROW
+       EXECUTE PROCEDURE 
+       noup ('COL1');
+
+-- Now Try
+INSERT INTO TEST VALUES (10,20,30);
+UPDATE TEST SET COL1 = 5;

diff --git a/contrib/noupdate/noup.source b/contrib/noupdate/noup.source
new file mode 100644 (file)
index 0000000..0aa875d
--- /dev/null
+++ b/contrib/noupdate/noup.source
@@ -0,0 +1,7 @@
+DROP FUNCTION noup ();
+
+CREATE FUNCTION noup ()
+       RETURNS opaque
+       AS '_OBJWD_/noup_DLSUFFIX_'
+       LANGUAGE 'c'
+;