Make FLOAT(p) measure the precision p in bits, not decimal digits, to

match the SQL standard.  Document FLOAT and FLOAT(p) notations in
datatype.sgml.  Per recent pghackers discussion.

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index d96c14e060e26756f895330c025bce864f5b9f29..05faaa422f37905586c1ed210485535febd181b7 100644 (file)
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1,5 +1,5 @@
 
 
  
@@ -607,16 +607,47 @@ NUMERIC
     
 
     
-     Normally, the real type has a range of at least
-     -1E+37 to +1E+37 with a precision of at least 6 decimal digits.  The
-     double precision type normally has a range of around
-     -1E+308 to +1E+308 with a precision of at least 15 digits.  Values that
+     On most platforms, the real type has a range of at least
+     1E-37 to 1E+37 with a precision of at least 6 decimal digits.  The
+     double precision type typically has a range of around
+     1E-307 to 1E+308 with a precision of at least 15 digits.  Values that
      are too large or too small will cause an error.  Rounding may
      take place if the precision of an input number is too high.
      Numbers too close to zero that are not representable as distinct
      from zero will cause an underflow error.
     
 
+    
+     PostgreSQL also supports the SQL-standard
+     notations float and
+     float(p) for specifying
+     inexact numeric types.  Here, p specifies
+     the minimum acceptable precision in binary digits.
+     PostgreSQL accepts 
+     float(1) to float(24) as selecting the
+     real type, while 
+     float(25) to float(53) select
+     double precision.  Values of p
+     outside the allowed range draw an error.
+     float with no precision specified is taken to mean
+     double precision.
+    
+
+    
+     
+      Prior to PostgreSQL 7.4, the precision in
+      float(p) was taken to mean
+      so many decimal digits.  This has been corrected to match the SQL
+      standard, which specifies that the precision is measured in binary
+      digits.  The assumption that real and
+      double precision have exactly 24 and 53 bits in the
+      mantissa respectively is correct for IEEE-standard floating point
+      implementations.  On non-IEEE platforms it may be off a little, but
+      for simplicity the same ranges of p are used
+      on all platforms.
+     
+    
+
    
 
    

diff --git a/doc/src/sgml/release.sgml b/doc/src/sgml/release.sgml
index db59de76f6475a4726afcffe2258051ac4aa5226..382029b81ffc31a73c52a32bf83dd1e9e18c03e7 100644 (file)
--- a/doc/src/sgml/release.sgml
+++ b/doc/src/sgml/release.sgml
@@ -1,5 +1,5 @@
 
 
 
@@ -24,6 +24,7 @@ CDATA means the content is "SGML-free", so you can write without
 worries about funny characters.
 -->
 
+Precision in FLOAT(p) is now interpreted as bits, not decimal digits
 Functional indexes have been generalized into expressional indexes
 CHAR(n) to TEXT conversion automatically strips trailing blanks
 Pattern matching operations can use indexes regardless of locale


diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y

index ec2f331609147a9e726f367b14ed33be1f59d65a..f8958d5878329309b019d60135c744951f79f97d 100644 (file)

--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.416 2003/05/29 20:40:36 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.417 2003/06/17 23:12:36 tgl Exp $
  *
  * HISTORY
  *   AUTHOR            DATE            MAJOR EVENT
@@ -5051,8 +5051,8 @@ GenericType:
 
 /* SQL92 numeric data types
  * Check FLOAT() precision limits assuming IEEE floating types.
- * Provide real DECIMAL() and NUMERIC() implementations now - Jan 1998-12-30
  * - thomas 1997-09-18
+ * Provide real DECIMAL() and NUMERIC() implementations now - Jan 1998-12-30
  */
 Numeric:   INT_P
                {
@@ -5107,14 +5107,14 @@ opt_float:  '(' Iconst ')'
                {
                    if ($2 < 1)
                        elog(ERROR,
-                           "precision for FLOAT must be at least 1");
-                   else if ($2 < 7)
+                           "precision for FLOAT must be at least 1 bit");
+                   else if ($2 <= 24)
                        $$ = SystemTypeName("float4");
-                   else if ($2 < 16)
+                   else if ($2 <= 53)
                        $$ = SystemTypeName("float8");
                    else
                        elog(ERROR,
-                           "precision for FLOAT must be less than 16");
+                           "precision for FLOAT must be less than 54 bits");
                }
            | /*EMPTY*/
                {

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ec2f331609147a9e726f367b14ed33be1f59d65a..f8958d5878329309b019d60135c744951f79f97d 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.416 2003/05/29 20:40:36 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.417 2003/06/17 23:12:36 tgl Exp $
  *
  * HISTORY
  *   AUTHOR            DATE            MAJOR EVENT
@@ -5051,8 +5051,8 @@ GenericType:
 
 /* SQL92 numeric data types
  * Check FLOAT() precision limits assuming IEEE floating types.
- * Provide real DECIMAL() and NUMERIC() implementations now - Jan 1998-12-30
  * - thomas 1997-09-18
+ * Provide real DECIMAL() and NUMERIC() implementations now - Jan 1998-12-30
  */
 Numeric:   INT_P
                {
@@ -5107,14 +5107,14 @@ opt_float:  '(' Iconst ')'
                {
                    if ($2 < 1)
                        elog(ERROR,
-                           "precision for FLOAT must be at least 1");
-                   else if ($2 < 7)
+                           "precision for FLOAT must be at least 1 bit");
+                   else if ($2 <= 24)
                        $$ = SystemTypeName("float4");
-                   else if ($2 < 16)
+                   else if ($2 <= 53)
                        $$ = SystemTypeName("float8");
                    else
                        elog(ERROR,
-                           "precision for FLOAT must be less than 16");
+                           "precision for FLOAT must be less than 54 bits");
                }
            | /*EMPTY*/
                {