Document the always-true-but-previously-undocumented fact that PQfnumber()

will downcase the supplied field name unless it is double-quoted.  Also,
upgrade the routine's handling of double quotes to match the backend,
in particular support doubled double quotes within quoted identifiers.
Per pgsql-interfaces discussion a couple weeks ago.

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 37e1fffb5fe85f3ccdb7418b8ea02e88279c4e4b..3bbad0c45999cfa2dc74ad9940001343a6eda9c2 100644 (file)
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1,5 +1,5 @@
 
 
  
@@ -1553,8 +1553,7 @@ NULL is returned if the column number is out of range.
 PQfnumberPQfnumber
 
 
-            Returns  the  column number
-          associated with the given column name.
+          Returns the column number associated with the given column name.
 
 int PQfnumber(const PGresult *res,
               const char *column_name);
@@ -1564,6 +1563,24 @@ int PQfnumber(const PGresult *res,
 
         -1 is returned if the given name does not match any column.
 
+
+
+        The given name is treated like an identifier in an SQL command,
+   that is, it is downcased unless double-quoted.  For example,
+   given a query result generated from the SQL command
+
+select 1 as FOO, 2 as "BAR";
+
+        we would have the results:
+
+PQfname(res, 0)              foo
+PQfname(res, 1)              BAR
+PQfnumber(res, "FOO")        0
+PQfnumber(res, "foo")        0
+PQfnumber(res, "BAR")        -1
+PQfnumber(res, "\"BAR\"")    1
+
+
 
 
 

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index 6d159a9a35a5569a770525edddf4f312b59d7a86..810a753ed3c7565e1dd7194daf7b60a5922708be 100644 (file)
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.150 2003/10/03 18:26:14 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.151 2003/10/04 21:05:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1803,32 +1803,80 @@ PQfname(const PGresult *res, int field_num)
 }
 
 /*
- * returns -1 on a bad field name
+ * PQfnumber: find column number given column name
+ *
+ * The column name is parsed as if it were in a SQL statement, including
+ * case-folding and double-quote processing.  But note a possible gotcha:
+ * downcasing in the frontend might follow different locale rules than
+ * downcasing in the backend...
+ *
+ * Returns -1 if no match.  In the present backend it is also possible
+ * to have multiple matches, in which case the first one is found.
  */
 int
 PQfnumber(const PGresult *res, const char *field_name)
 {
-   int         i;
    char       *field_case;
+   bool        in_quotes;
+   char       *iptr;
+   char       *optr;
+   int         i;
 
    if (!res)
        return -1;
 
+   /*
+    * Note: it is correct to reject a zero-length input string; the proper
+    * input to match a zero-length field name would be "".
+    */
    if (field_name == NULL ||
        field_name[0] == '\0' ||
        res->attDescs == NULL)
        return -1;
 
+   /*
+    * Note: this code will not reject partially quoted strings, eg
+    * foo"BAR"foo will become fooBARfoo when it probably ought to be
+    * an error condition.
+    */
    field_case = strdup(field_name);
-   if (*field_case == '"')
+   if (field_case == NULL)
+       return -1;              /* grotty */
+
+   in_quotes = false;
+   optr = field_case;
+   for (iptr = field_case; *iptr; iptr++)
    {
-       strcpy(field_case, field_case + 1);
-       *(field_case + strlen(field_case) - 1) = '\0';
+       char    c = *iptr;
+
+       if (in_quotes)
+       {
+           if (c == '"')
+           {
+               if (iptr[1] == '"')
+               {
+                   /* doubled quotes become a single quote */
+                   *optr++ = '"';
+                   iptr++;
+               }
+               else
+                   in_quotes = false;
+           }
+           else
+               *optr++ = c;
+       }
+       else if (c == '"')
+       {
+           in_quotes = true;
+       }
+       else
+       {
+           if (isupper((unsigned char) c))
+               c = tolower((unsigned char) c);
+           *optr++ = c;
+       }
    }
-   else
-       for (i = 0; field_case[i]; i++)
-           if (isupper((unsigned char) field_case[i]))
-               field_case[i] = tolower((unsigned char) field_case[i]);
+   *optr = '\0';
 
    for (i = 0; i < res->numAttributes; i++)
    {