Use wrappers of PG_DETOAST_DATUM_PACKED() more.

This makes almost all core code follow the policy introduced in the
previous commit.  Specific decisions:

- Text search support functions with char* and length arguments, such as
  prsstart and lexize, may receive unaligned strings.  I doubt
  maintainers of non-core text search code will notice.

- Use plain VARDATA() on values detoasted or synthesized earlier in the
  same function.  Use VARDATA_ANY() on varlenas sourced outside the
  function, even if they happen to always have four-byte headers.  As an
  exception, retain the universal practice of using VARDATA() on return
  values of SendFunctionCall().

- Retain PG_GETARG_BYTEA_P() in pageinspect.  (Page images are too large
  for a one-byte header, so this misses no optimization.)  Sites that do
  not call get_page_from_raw() typically need the four-byte alignment.

- For now, do not change btree_gist.  Its use of four-byte headers in
  memory is partly entangled with storage of 4-byte headers inside
  GBT_VARKEY, on disk.

- For now, do not change gtrgm_consistent() or gtrgm_distance().  They
  incorporate the varlena header into a cache, and there are multiple
  credible implementation strategies to consider.

1 files changed, 5 insertions, 19 deletions

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 28b5745ba83..cd036afc004 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -2662,7 +2662,7 @@ bytea_catenate(bytea *t1, bytea *t2)
 }
 
 #define PG_STR_GET_BYTEA(str_) \
-	DatumGetByteaP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))
+	DatumGetByteaPP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))
 
 /*
  * bytea_substr()
@@ -2934,13 +2934,12 @@ byteaGetBit(PG_FUNCTION_ARGS)
 Datum
 byteaSetByte(PG_FUNCTION_ARGS)
 {
-	bytea	   *v = PG_GETARG_BYTEA_P(0);
+	bytea	   *res = PG_GETARG_BYTEA_P_COPY(0);
 	int32		n = PG_GETARG_INT32(1);
 	int32		newByte = PG_GETARG_INT32(2);
 	int			len;
-	bytea	   *res;
 
-	len = VARSIZE(v) - VARHDRSZ;
+	len = VARSIZE(res) - VARHDRSZ;
 
 	if (n < 0 || n >= len)
 		ereport(ERROR,
@@ -2949,12 +2948,6 @@ byteaSetByte(PG_FUNCTION_ARGS)
 						n, len - 1)));
 
 	/*
-	 * Make a copy of the original varlena.
-	 */
-	res = (bytea *) palloc(VARSIZE(v));
-	memcpy((char *) res, (char *) v, VARSIZE(v));
-
-	/*
 	 * Now set the byte.
 	 */
 	((unsigned char *) VARDATA(res))[n] = newByte;
@@ -2973,17 +2966,16 @@ byteaSetByte(PG_FUNCTION_ARGS)
 Datum
 byteaSetBit(PG_FUNCTION_ARGS)
 {
-	bytea	   *v = PG_GETARG_BYTEA_P(0);
+	bytea	   *res = PG_GETARG_BYTEA_P_COPY(0);
 	int32		n = PG_GETARG_INT32(1);
 	int32		newBit = PG_GETARG_INT32(2);
-	bytea	   *res;
 	int			len;
 	int			oldByte,
 				newByte;
 	int			byteNo,
 				bitNo;
 
-	len = VARSIZE(v) - VARHDRSZ;
+	len = VARSIZE(res) - VARHDRSZ;
 
 	if (n < 0 || n >= len * 8)
 		ereport(ERROR,
@@ -3003,12 +2995,6 @@ byteaSetBit(PG_FUNCTION_ARGS)
 				 errmsg("new bit must be 0 or 1")));
 
 	/*
-	 * Make a copy of the original varlena.
-	 */
-	res = (bytea *) palloc(VARSIZE(v));
-	memcpy((char *) res, (char *) v, VARSIZE(v));
-
-	/*
 	 * Update the byte.
 	 */
 	oldByte = ((unsigned char *) VARDATA(res))[byteNo];