Change lpad() and rpad() to behave more Oracle-compatibly when target

length is less than original string length.

diff --git a/src/backend/utils/adt/oracle_compat.c b/src/backend/utils/adt/oracle_compat.c
index 19c37edd9719c13f75c82df4d184bd684c00fd5f..3fb3e5b093c26e2a4c3add9a06abe811d002deb5 100644 (file)
--- a/src/backend/utils/adt/oracle_compat.c
+++ b/src/backend/utils/adt/oracle_compat.c
@@ -5,10 +5,10 @@
  *
  */
 
-#include <ctype.h>
-
 #include "postgres.h"
 
+#include <ctype.h>
+
 #include "utils/builtins.h"
 
 
@@ -140,7 +140,8 @@ initcap(PG_FUNCTION_ARGS)
  * Purpose:
  *
  *      Returns string1, left-padded to length len with the sequence of
- *      characters in string2.
+ *      characters in string2.  If len is less than the length of string1,
+ *      instead truncate (on the right) to len.
  *
  ********************************************************************/
 
@@ -153,31 +154,49 @@ lpad(PG_FUNCTION_ARGS)
        text       *ret;
        char       *ptr1,
                           *ptr2,
+                          *ptr2end,
                           *ptr_ret;
        int                     m,
-                               n;
+                               s1len,
+                               s2len;
+
+       /* Negative len is silently taken as zero */
+       if (len < 0)
+               len = 0;
+
+       s1len = VARSIZE(string1) - VARHDRSZ;
+       if (s1len < 0)
+               s1len = 0;                              /* shouldn't happen */
+
+       s2len = VARSIZE(string2) - VARHDRSZ;
+       if (s2len < 0)
+               s2len = 0;                              /* shouldn't happen */
 
-       if (((VARSIZE(string1) - VARHDRSZ) < 0) ||
-               ((m = len - (VARSIZE(string1) - VARHDRSZ)) <= 0) ||
-               ((VARSIZE(string2) - VARHDRSZ) <= 0))
-               PG_RETURN_TEXT_P(string1);
+       if (s1len > len)
+               s1len = len;                    /* truncate string1 to len chars */
+
+       if (s2len <= 0)
+               len = s1len;                    /* nothing to pad with, so don't pad */
 
        ret = (text *) palloc(VARHDRSZ + len);
        VARATT_SIZEP(ret) = VARHDRSZ + len;
 
+       m = len - s1len;
+
        ptr2 = VARDATA(string2);
+       ptr2end = ptr2 + s2len;
        ptr_ret = VARDATA(ret);
 
        while (m--)
        {
-               *ptr_ret++ = *ptr2;
-               ptr2 = (ptr2 == VARDATA(string2) + VARSIZE(string2) - VARHDRSZ - 1) ? VARDATA(string2) : ++ptr2;
+               *ptr_ret++ = *ptr2++;
+               if (ptr2 == ptr2end)    /* wrap around at end of s2 */
+                       ptr2 = VARDATA(string2);
        }
 
-       n = VARSIZE(string1) - VARHDRSZ;
        ptr1 = VARDATA(string1);
 
-       while (n--)
+       while (s1len--)
                *ptr_ret++ = *ptr1++;
 
        PG_RETURN_TEXT_P(ret);
@@ -195,7 +214,8 @@ lpad(PG_FUNCTION_ARGS)
  * Purpose:
  *
  *      Returns string1, right-padded to length len with the sequence of
- *      characters in string2.
+ *      characters in string2.  If len is less than the length of string1,
+ *      instead truncate (on the right) to len.
  *
  ********************************************************************/
 
@@ -208,31 +228,49 @@ rpad(PG_FUNCTION_ARGS)
        text       *ret;
        char       *ptr1,
                           *ptr2,
+                          *ptr2end,
                           *ptr_ret;
        int                     m,
-                               n;
+                               s1len,
+                               s2len;
+
+       /* Negative len is silently taken as zero */
+       if (len < 0)
+               len = 0;
+
+       s1len = VARSIZE(string1) - VARHDRSZ;
+       if (s1len < 0)
+               s1len = 0;                              /* shouldn't happen */
 
-       if (((VARSIZE(string1) - VARHDRSZ) < 0) ||
-               ((m = len - (VARSIZE(string1) - VARHDRSZ)) <= 0) ||
-               ((VARSIZE(string2) - VARHDRSZ) <= 0))
-               PG_RETURN_TEXT_P(string1);
+       s2len = VARSIZE(string2) - VARHDRSZ;
+       if (s2len < 0)
+               s2len = 0;                              /* shouldn't happen */
+
+       if (s1len > len)
+               s1len = len;                    /* truncate string1 to len chars */
+
+       if (s2len <= 0)
+               len = s1len;                    /* nothing to pad with, so don't pad */
 
        ret = (text *) palloc(VARHDRSZ + len);
        VARATT_SIZEP(ret) = VARHDRSZ + len;
 
-       n = VARSIZE(string1) - VARHDRSZ;
+       m = len - s1len;
+
        ptr1 = VARDATA(string1);
        ptr_ret = VARDATA(ret);
 
-       while (n--)
+       while (s1len--)
                *ptr_ret++ = *ptr1++;
 
        ptr2 = VARDATA(string2);
+       ptr2end = ptr2 + s2len;
 
        while (m--)
        {
-               *ptr_ret++ = *ptr2;
-               ptr2 = (ptr2 == VARDATA(string2) + VARSIZE(string2) - VARHDRSZ - 1) ? VARDATA(string2) : ++ptr2;
+               *ptr_ret++ = *ptr2++;
+               if (ptr2 == ptr2end)    /* wrap around at end of s2 */
+                       ptr2 = VARDATA(string2);
        }
 
        PG_RETURN_TEXT_P(ret);