Make compression use the defaults functions

.unreleased/pr_6696

@@ -0,0 +1 @@
+Implements: #6696 Improve defaults for compression segment_by and order_by

sql/compression_defaults.sql

@@ -45,10 +45,10 @@ BEGIN
     INNER JOIN
       pg_attribute a on (a.attnum = i.attnum AND a.attrelid = relation)
     --right now stats are from the hypertable itself. Use chunks in the future.
-    INNER JOIN pg_statistic s ON (s.staattnum = a.attnum and s.starelid = relation)
+    INNER JOIN pg_stats s ON (s.attname = a.attname and s.schemaname = _schema_name and s.tablename = _table_name)
     WHERE
       a.attname NOT IN (SELECT column_name FROM _timescaledb_catalog.dimension d WHERE d.hypertable_id = _hypertable_row.id)
-      AND s.stadistinct > 1
+      AND s.n_distinct > 1
     ORDER BY i.pos
     LIMIT 1;
 
@@ -75,10 +75,10 @@ BEGIN
     INNER JOIN
       pg_attribute a on (a.attnum = i.attnum AND a.attrelid = relation)
     --right now stats are from the hypertable itself. Use chunks in the future.
-    INNER JOIN pg_statistic s ON (s.staattnum = a.attnum and s.starelid = relation)
+    INNER JOIN pg_stats s ON (s.attname = a.attname and s.schemaname = _schema_name and s.tablename = _table_name)
     WHERE
       a.attname NOT IN (SELECT column_name FROM _timescaledb_catalog.dimension d WHERE d.hypertable_id = _hypertable_row.id)
-      AND s.stadistinct > 1
+      AND s.n_distinct > 1
     ORDER BY i.pos
     LIMIT 1;
 
@@ -106,10 +106,10 @@ BEGIN
     LEFT JOIN
       pg_catalog.pg_attrdef ad ON (ad.adrelid = relation AND ad.adnum = a.attnum)
     LEFT JOIN
-      pg_statistic s ON (s.staattnum = a.attnum and s.starelid = relation)
+      pg_stats s ON (s.attname = a.attname and s.schemaname = _schema_name and s.tablename = _table_name)
     WHERE
       a.attname NOT IN (SELECT column_name FROM _timescaledb_catalog.dimension d WHERE d.hypertable_id = _hypertable_row.id)
-      AND s.stadistinct is null
+      AND s.n_distinct is null
       AND a.attidentity = '' AND (ad.adbin IS NULL OR pg_get_expr(adbin, adrelid) not like 'nextval%')
     ORDER BY i.pos
     LIMIT 1;
@@ -141,10 +141,10 @@ BEGIN
     LEFT JOIN
       pg_catalog.pg_attrdef ad ON (ad.adrelid = relation AND ad.adnum = a.attnum)
     LEFT JOIN
-      pg_statistic s ON (s.staattnum = a.attnum and s.starelid = relation)
+      pg_stats s ON (s.attname = a.attname and s.schemaname = _schema_name and s.tablename = _table_name)
     WHERE
       a.attname NOT IN (SELECT column_name FROM _timescaledb_catalog.dimension d WHERE d.hypertable_id = _hypertable_row.id)
-      AND s.stadistinct is null
+      AND s.n_distinct is null
       AND a.attidentity = '' AND (ad.adbin IS NULL OR pg_get_expr(adbin, adrelid) not like 'nextval%')
     ORDER BY i.pos
     LIMIT 1;
@@ -285,12 +285,12 @@ BEGIN
 
     --add DESC to any dimensions
     SELECT
-      array_agg(
+      coalesce(array_agg(
       CASE WHEN d.column_name IS NULL THEN
-        a.colname
+        format('%I', a.colname)
       ELSE
-        a.colname || ' DESC'
-      END ORDER BY pos) INTO STRICT _orderby_clauses
+        format('%I DESC', a.colname)
+      END ORDER BY pos), array[]::text[]) INTO STRICT _orderby_clauses
     FROM unnest(_orderby_names) WITH ORDINALITY as a(colname, pos)
     LEFT JOIN _timescaledb_catalog.dimension d ON (d.column_name = a.colname AND d.hypertable_id = _hypertable_row.id);
 

src/compression_with_clause.c

@@ -176,8 +176,8 @@ throw_order_by_error(char *order_by)
 }
 
 /* compress_orderby is parsed same as order by in select queries */
-static OrderBySettings
-parse_order_collist(char *inpstr, Hypertable *hypertable)
+OrderBySettings
+ts_compress_parse_order_collist(char *inpstr, Hypertable *hypertable)
 {
 	StringInfoData buf;
 	List *parsed;
@@ -322,13 +322,9 @@ ts_compress_hypertable_parse_segment_by(WithClauseResult *parsed_options, Hypert
 OrderBySettings
 ts_compress_hypertable_parse_order_by(WithClauseResult *parsed_options, Hypertable *hypertable)
 {
-	if (parsed_options[CompressOrderBy].is_default == false)
-	{
-		Datum textarg = parsed_options[CompressOrderBy].parsed;
-		return parse_order_collist(TextDatumGetCString(textarg), hypertable);
-	}
-	else
-		return (OrderBySettings){ 0 };
+	Ensure(parsed_options[CompressOrderBy].is_default == false, "with clause is not default");
+	Datum textarg = parsed_options[CompressOrderBy].parsed;
+	return ts_compress_parse_order_collist(TextDatumGetCString(textarg), hypertable);
 }
 
 /* returns List of CompressedParsedCol

src/compression_with_clause.h

@@ -44,3 +44,5 @@ ts_compress_hypertable_parse_order_by(WithClauseResult *parsed_options, Hypertab
 extern TSDLLEXPORT Interval *
 ts_compress_hypertable_parse_chunk_time_interval(WithClauseResult *parsed_options,
 												 Hypertable *hypertable);
+extern TSDLLEXPORT OrderBySettings ts_compress_parse_order_collist(char *inpstr,
+																   Hypertable *hypertable);

src/guc.c

@@ -5,9 +5,13 @@
  */
 #include <postgres.h>
 #include <utils/guc.h>
+#include <utils/varlena.h>
+#include <utils/regproc.h>
+#include <parser/parse_func.h>
 #include <miscadmin.h>
 
 #include "guc.h"
+#include "extension.h"
 #include "license_guc.h"
 #include "config.h"
 #include "hypertable_cache.h"
@@ -76,6 +80,8 @@ TSDLLEXPORT bool ts_guc_enable_bulk_decompression = true;
 TSDLLEXPORT bool ts_guc_auto_sparse_indexes = true;
 TSDLLEXPORT int ts_guc_bgw_log_level = WARNING;
 TSDLLEXPORT bool ts_guc_enable_skip_scan = true;
+static char *ts_guc_default_segmentby_fn = NULL;
+static char *ts_guc_default_orderby_fn = NULL;
 /* default value of ts_guc_max_open_chunks_per_insert and ts_guc_max_cached_chunks_per_hypertable
  * will be set as their respective boot-value when the GUC mechanism starts up */
 int ts_guc_max_open_chunks_per_insert;
@@ -218,6 +224,90 @@ assign_max_open_chunks_per_insert_hook(int newval, void *extra)
 	validate_chunk_cache_sizes(ts_guc_max_cached_chunks_per_hypertable, newval);
 }
 
+static Oid
+get_segmentby_func(char *input_name)
+{
+	List *namelist = NIL;
+
+	if (strlen(input_name) == 0)
+	{
+		return InvalidOid;
+	}
+
+#if PG16_LT
+	namelist = stringToQualifiedNameList(input_name);
+#else
+	namelist = stringToQualifiedNameList(input_name, NULL);
+#endif
+	Oid argtyp[] = { REGCLASSOID };
+	return LookupFuncName(namelist, lengthof(argtyp), argtyp, true);
+}
+
+static bool
+check_segmentby_func(char **newval, void **extra, GucSource source)
+{
+	/* if the extension doesn't exist you can't check for the function, have to take it on faith */
+	if (ts_extension_is_loaded())
+	{
+		Oid segment_func_oid = get_segmentby_func(*newval);
+
+		if (strlen(*newval) > 0 && !OidIsValid(segment_func_oid))
+		{
+			GUC_check_errdetail("Function \"%s\" does not exist.", *newval);
+			return false;
+		}
+	}
+	return true;
+}
+
+Oid
+ts_guc_default_segmentby_fn_oid()
+{
+	return get_segmentby_func(ts_guc_default_segmentby_fn);
+}
+
+static Oid
+get_orderby_func(char *input_name)
+{
+	List *namelist = NIL;
+
+	if (strlen(input_name) == 0)
+	{
+		return InvalidOid;
+	}
+
+#if PG16_LT
+	namelist = stringToQualifiedNameList(input_name);
+#else
+	namelist = stringToQualifiedNameList(input_name, NULL);
+#endif
+	Oid argtyp[] = { REGCLASSOID, TEXTARRAYOID };
+	return LookupFuncName(namelist, lengthof(argtyp), argtyp, true);
+}
+
+static bool
+check_orderby_func(char **newval, void **extra, GucSource source)
+{
+	/* if the extension doesn't exist you can't check for the function, have to take it on faith */
+	if (ts_extension_is_loaded())
+	{
+		Oid func_oid = get_orderby_func(*newval);
+
+		if (strlen(*newval) > 0 && !OidIsValid(func_oid))
+		{
+			GUC_check_errdetail("Function \"%s\" does not exist.", *newval);
+			return false;
+		}
+	}
+	return true;
+}
+
+Oid
+ts_guc_default_orderby_fn_oid()
+{
+	return get_orderby_func(ts_guc_default_orderby_fn);
+}
+
 void
 _guc_init(void)
 {
@@ -570,6 +660,32 @@ _guc_init(void)
 							 NULL);
 #endif
 
+	DefineCustomStringVariable(/* name= */ MAKE_EXTOPTION("compression_segmentby_default_function"),
+							   /* short_desc= */ "Function that sets default segment_by",
+							   /* long_desc= */
+							   "Function to use for calculating default segment_by setting for "
+							   "compression",
+							   /* valueAddr= */ &ts_guc_default_segmentby_fn,
+							   /* Value= */ "_timescaledb_functions.get_segmentby_defaults",
+							   /* context= */ PGC_USERSET,
+							   /* flags= */ 0,
+							   /* check_hook= */ check_segmentby_func,
+							   /* assign_hook= */ NULL,
+							   /* show_hook= */ NULL);
+
+	DefineCustomStringVariable(/* name= */ MAKE_EXTOPTION("compression_orderby_default_function"),
+							   /* short_desc= */ "Function that sets default order_by",
+							   /* long_desc= */
+							   "Function to use for calculating default order_by setting for "
+							   "compression",
+							   /* valueAddr= */ &ts_guc_default_orderby_fn,
+							   /* Value= */ "_timescaledb_functions.get_orderby_defaults",
+							   /* context= */ PGC_USERSET,
+							   /* flags= */ 0,
+							   /* check_hook= */ check_orderby_func,
+							   /* assign_hook= */ NULL,
+							   /* show_hook= */ NULL);
+
 	DefineCustomStringVariable(/* name= */ MAKE_EXTOPTION("license"),
 							   /* short_desc= */ "TimescaleDB license type",
 							   /* long_desc= */ "Determines which features are enabled",

src/guc.h

@@ -94,3 +94,5 @@ typedef enum
 } FeatureFlagType;
 
 extern TSDLLEXPORT void ts_feature_flag_check(FeatureFlagType);
+extern TSDLLEXPORT Oid ts_guc_default_segmentby_fn_oid(void);
+extern TSDLLEXPORT Oid ts_guc_default_orderby_fn_oid(void);

src/ts_catalog/array_utils.c

@@ -89,6 +89,42 @@ ts_array_is_member(ArrayType *arr, const char *name)
 	return ret;
 }
 
+extern TSDLLEXPORT void
+ts_array_append_stringinfo(ArrayType *arr, StringInfo info)
+{
+	bool first = true;
+	Datum datum;
+	bool null;
+
+	if (!arr)
+		return;
+
+	Assert(ARR_NDIM(arr) <= 1);
+	Assert(arr->elemtype == TEXTOID);
+
+	ArrayIterator it = array_create_iterator(arr, 0, NULL);
+	while (array_iterate(it, &datum, &null))
+	{
+		Assert(!null);
+		/*
+		 * Our internal catalog arrays should either be NULL or
+		 * have non-NULL members. During normal operation it should
+		 * never have NULL members. If we have NULL members either
+		 * the catalog is corrupted or some catalog tampering has
+		 * happened.
+		 */
+		Ensure(!null, "array element was NULL");
+		if (!first)
+			appendStringInfoString(info, ", ");
+		else
+			first = false;
+
+		appendStringInfo(info, "%s", TextDatumGetCString(datum));
+	}
+
+	array_free_iterator(it);
+}
+
 extern TSDLLEXPORT int
 ts_array_position(ArrayType *arr, const char *name)
 {

src/ts_catalog/array_utils.h

@@ -20,6 +20,7 @@
 extern TSDLLEXPORT int ts_array_length(ArrayType *arr);
 extern TSDLLEXPORT bool ts_array_equal(ArrayType *left, ArrayType *right);
 extern TSDLLEXPORT bool ts_array_is_member(ArrayType *arr, const char *name);
+extern TSDLLEXPORT void ts_array_append_stringinfo(ArrayType *arr, StringInfo info);
 extern TSDLLEXPORT int ts_array_position(ArrayType *arr, const char *name);
 
 extern TSDLLEXPORT bool ts_array_get_element_bool(ArrayType *arr, int position);