The new LZ compression and an lztext data type based on it.

Jan

src/backend/utils/adt/lztext.c

@@ -0,0 +1,266 @@
+/* ----------
+ * lztext.c -
+ *
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/Attic/lztext.c,v 1.1 1999/11/17 21:21:50 wieck Exp $
+ *
+ *	Text type with internal LZ compressed representation. Uses the
+ *	standard PostgreSQL compression method.
+ * ----------
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <errno.h>
+
+#include "postgres.h"
+#include "utils/builtins.h"
+#include "utils/palloc.h"
+#include "utils/pg_lzcompress.h"
+
+
+/* ----------
+ * lztextin -
+ *
+ *		Input function for datatype lztext
+ * ----------
+ */
+lztext *
+lztextin(char *str)
+{
+	lztext		   *result;
+	int32			rawsize;
+	lztext		   *tmp;
+	int				tmp_size;
+
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (str == NULL)
+		return NULL;
+
+	/* ----------
+	 * Determine input size and eventually tuple size
+	 * ----------
+	 */
+	rawsize = strlen(str);
+	tmp_size = PGLZ_MAX_OUTPUT(rawsize);
+
+	/* ----------
+	 * Allocate a temporary result and compress into it
+	 * ----------
+	 */
+	tmp = (lztext *) palloc(tmp_size);
+	pglz_compress(str, rawsize, tmp, NULL);
+
+	/* ----------
+	 * If we miss less than x% bytes at the end of the temp value,
+	 * so be it. Therefore we save a memcpy().
+	 * ----------
+	 */
+	if (tmp_size - tmp->varsize < 256 || 
+					tmp_size - tmp->varsize < tmp_size / 4)
+	{
+		result = tmp;
+	} else {
+		result = (lztext *) palloc(tmp->varsize);
+		memcpy(result, tmp, tmp->varsize);
+		pfree(tmp);
+	}
+
+	return result;
+}
+
+
+/* ----------
+ * lztextout -
+ *
+ *		Output function for data type lztext
+ * ----------
+ */
+char *
+lztextout(lztext *lz)
+{
+	char			*result;
+
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (lz == NULL)
+	{
+		result = (char *) palloc(2);
+		result[0] = '-';
+		result[1] = '\0';
+		return result;
+	}
+
+	/* ----------
+	 * Allocate the result string - the required size is remembered
+	 * in the lztext header so we don't need a temporary buffer or
+	 * have to diddle with realloc's.
+	 * ----------
+	 */
+	result = (char *) palloc(PGLZ_RAW_SIZE(lz) + 1);
+
+	/* ----------
+	 * Decompress and add terminating ZERO
+	 * ----------
+	 */
+	pglz_decompress(lz, result);
+	result[lz->rawsize] = '\0';
+
+	/* ----------
+	 * Return the result
+	 * ----------
+	 */
+	return result;
+}
+
+
+/* ----------
+ * lztextlen -
+ *
+ *	Logical length of lztext field (it's the uncompressed size
+ *	of the original data).
+ * ----------
+ */
+int32
+lztextlen(lztext *lz)
+{
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (lz == NULL)
+		return 0;
+
+	/* ----------
+	 * without multibyte support, it's the remembered rawsize
+	 * ----------
+	 */
+	return lz->rawsize;
+}
+
+
+/* ----------
+ * lztextoctetlen -
+ *
+ *	Physical length of lztext field (it's the compressed size
+ *	plus the rawsize field).
+ * ----------
+ */
+int32
+lztextoctetlen(lztext *lz)
+{
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (lz == NULL)
+		return 0;
+
+	/* ----------
+	 * Return the varsize minus the VARSIZE field itself.
+	 * ----------
+	 */
+	return lz->varsize - sizeof(int32);
+}
+
+
+/* ----------
+ * text_lztext -
+ *
+ *	Convert text to lztext
+ * ----------
+ */
+lztext *
+text_lztext(text *txt)
+{
+	lztext		   *result;
+	int32			rawsize;
+	lztext		   *tmp;
+	int				tmp_size;
+	char		   *str;
+
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (txt == NULL)
+		return NULL;
+
+	/* ----------
+	 * Determine input size and eventually tuple size
+	 * ----------
+	 */
+	rawsize  = VARSIZE(txt) - VARHDRSZ;
+	str      = VARDATA(txt);
+	tmp_size = PGLZ_MAX_OUTPUT(rawsize);
+
+	/* ----------
+	 * Allocate a temporary result and compress into it
+	 * ----------
+	 */
+	tmp = (lztext *) palloc(tmp_size);
+	pglz_compress(str, rawsize, tmp, NULL);
+
+	/* ----------
+	 * If we miss less than x% bytes at the end of the temp value,
+	 * so be it. Therefore we save a memcpy().
+	 * ----------
+	 */
+	if (tmp_size - tmp->varsize < 256 || 
+					tmp_size - tmp->varsize < tmp_size / 4)
+	{
+		result = tmp;
+	} else {
+		result = (lztext *) palloc(tmp->varsize);
+		memcpy(result, tmp, tmp->varsize);
+		pfree(tmp);
+	}
+
+	return result;
+
+	
+}
+
+
+/* ----------
+ * lztext_text -
+ *
+ *	Convert lztext to text
+ * ----------
+ */
+text *
+lztext_text(lztext *lz)
+{
+	text	   *result;
+
+	/* ----------
+	 * Handle NULL
+	 * ----------
+	 */
+	if (lz == NULL)
+		return NULL;
+
+	/* ----------
+	 * Allocate and initialize the text result
+	 * ----------
+	 */
+	result = (text *) palloc(lz->rawsize + VARHDRSZ + 1);
+	VARSIZE(result) = lz->rawsize + VARHDRSZ;
+
+	/* ----------
+	 * Decompress directly into the text data area.
+	 * ----------
+	 */
+	pglz_decompress(lz, VARDATA(result));
+	VARDATA(result)[lz->rawsize] = 0;
+
+	return result;
+}
+
+