Skip the 'default row' pseudo-record where needed

The 'default row' record (which stores the default values of
instantly added columns when they were added) must be ignored
during normal operation.

Because btr_pcur_store_position() can theoretically be invoked
on the pseudo-record, we must check every caller of
btr_pcur_restore_position(). Similarly, when positioning the
cursor to the start of an index with btr_pcur_open_at_index_side(),
or when moving to the previous record, we must be careful to
skip the 'default row' record.

rec_is_default_row(): Check whether a leaf page record is the
'default row' pseudo-record.

row_import_set_sys_max_row_id(): Check for a table that is empty but
contains the 'default row' record.

IndexPurge::open(), row_merge_read_clustered_index(),
dict_stats_analyze_index_level(), row_sel_try_search_shortcut(),
row_sel(), sel_restore_position_for_mysql(), row_search_mvcc():
Skip the 'default row' pseudo-record.

fts_get_max_doc_id(): Assert that the 'default row' cannot exist
in the secondary index FTS_DOC_ID_INDEX(FTS_DOC_ID).

page_find_rec_max_not_deleted(): Assert that we are operating
on a leaf page. Also skip the 'default row' pseudo-record, not
only delete-marked records.

row_search_get_max_rec(): Assert that page_find_rec_max_not_deleted()
did not return any delete-marked or 'default row' record.

storage/innobase/dict/dict0stats.cc

@@ -1109,11 +1109,19 @@ dict_stats_analyze_index_level(
 	/* there should not be any pages on the left */
 	ut_a(btr_page_get_prev(page, mtr) == FIL_NULL);
 
-	/* check whether the first record on the leftmost page is marked
-	as such, if we are on a non-leaf level */
-	ut_a((level == 0)
-	     == !(REC_INFO_MIN_REC_FLAG & rec_get_info_bits(
-			  btr_pcur_get_rec(&pcur), page_is_comp(page))));
+	if (REC_INFO_MIN_REC_FLAG & rec_get_info_bits(
+		    btr_pcur_get_rec(&pcur), page_is_comp(page))) {
+		ut_ad(btr_pcur_is_on_user_rec(&pcur));
+		if (level == 0) {
+			/* Skip the 'default row' pseudo-record */
+			ut_ad(index->is_instant());
+			btr_pcur_move_to_next_user_rec(&pcur, mtr);
+		}
+	} else {
+		/* The first record on the leftmost page must be
+		marked as such on each level except the leaf level. */
+		ut_a(level == 0);
+	}
 
 	prev_rec = NULL;
 	prev_rec_is_copied = false;

storage/innobase/fts/fts0fts.cc

@@ -3599,6 +3599,8 @@ fts_get_max_doc_id(
 		return(0);
 	}
 
+	ut_ad(!index->is_instant());
+
 	dfield = dict_index_get_nth_field(index, 0);
 
 #if 0 /* This can fail when renaming a column to FTS_DOC_ID_COL_NAME. */
@@ -3633,6 +3635,7 @@ fts_get_max_doc_id(
 			goto func_exit;
 		}
 
+		ut_ad(!rec_is_default_row(rec, index));
 		offsets = rec_get_offsets(
 			rec, index, offsets, true, ULINT_UNDEFINED, &heap);
 

storage/innobase/include/rem0rec.h

@@ -33,6 +33,7 @@ Created 5/30/1994 Heikki Tuuri
 #include "rem0types.h"
 #include "mtr0types.h"
 #include "page0types.h"
+#include "dict0dict.h"
 #include "trx0types.h"
 #endif /*! UNIV_INNOCHECKSUM */
 #include <ostream>
@@ -768,6 +769,21 @@ rec_offs_comp(const ulint* offsets)
 	return(*rec_offs_base(offsets) & REC_OFFS_COMPACT);
 }
 
+/** Determine if the record is the 'default row' pseudo-record
+in the clustered index.
+@param[in]	rec	leaf page record
+@param[in]	index	index of the record
+@return	whether the record is the 'default row' pseudo-record */
+inline
+bool
+rec_is_default_row(const rec_t* rec, const dict_index_t* index)
+{
+	bool is = rec_get_info_bits(rec, dict_table_is_comp(index->table))
+		& REC_INFO_MIN_REC_FLAG;
+	ut_ad(!is || index->is_instant());
+	return is;
+}
+
 /******************************************************//**
 Gets the physical size of a field.
 @return length of field */

storage/innobase/include/rem0rec.ic

@@ -26,7 +26,6 @@ Created 5/30/1994 Heikki Tuuri
 
 #include "mach0data.h"
 #include "ut0byte.h"
-#include "dict0dict.h"
 #include "dict0boot.h"
 #include "btr0types.h"
 

storage/innobase/page/page0page.cc

@@ -2807,19 +2807,26 @@ page_find_rec_max_not_deleted(
 	const rec_t*	rec = page_get_infimum_rec(page);
 	const rec_t*	prev_rec = NULL; // remove warning
 
-	/* Because the page infimum is never delete-marked,
+	/* Because the page infimum is never delete-marked
+	and never the 'default row' pseudo-record (MIN_REC_FLAG)),
 	prev_rec will always be assigned to it first. */
-	ut_ad(!rec_get_deleted_flag(rec, page_rec_is_comp(rec)));
+	ut_ad(!rec_get_info_bits(rec, page_rec_is_comp(rec)));
+	ut_ad(page_is_leaf(page));
+
 	if (page_is_comp(page)) {
 		do {
-			if (!rec_get_deleted_flag(rec, true)) {
+			if (!(rec[-REC_NEW_INFO_BITS]
+			      & (REC_INFO_DELETED_FLAG
+				 | REC_INFO_MIN_REC_FLAG))) {
 				prev_rec = rec;
 			}
 			rec = page_rec_get_next_low(rec, true);
 		} while (rec != page + PAGE_NEW_SUPREMUM);
 	} else {
 		do {
-			if (!rec_get_deleted_flag(rec, false)) {
+			if (!(rec[-REC_OLD_INFO_BITS]
+			      & (REC_INFO_DELETED_FLAG
+				 | REC_INFO_MIN_REC_FLAG))) {
 				prev_rec = rec;
 			}
 			rec = page_rec_get_next_low(rec, false);

storage/innobase/row/row0import.cc

@@ -1439,6 +1439,11 @@ IndexPurge::open() UNIV_NOTHROW
 
 	btr_pcur_open_at_index_side(
 		true, m_index, BTR_MODIFY_LEAF, &m_pcur, true, 0, &m_mtr);
+	if (rec_is_default_row(btr_pcur_get_rec(&m_pcur), m_index)) {
+		ut_ad(btr_pcur_is_on_user_rec(&m_pcur));
+		/* Skip the 'default row' pseudo-record. */
+		btr_pcur_move_to_next_user_rec(&m_pcur, &m_mtr);
+	}
 }
 
 /**
@@ -2319,7 +2324,14 @@ row_import_set_sys_max_row_id(
 	rec = btr_pcur_get_rec(&pcur);
 
 	/* Check for empty table. */
-	if (!page_rec_is_infimum(rec)) {
+	if (page_rec_is_infimum(rec)) {
+		/* The table is empty. */
+		err = DB_SUCCESS;
+	} else if (rec_is_default_row(rec, index)) {
+		/* The clustered index contains the 'default row',
+		that is, the table is empty. */
+		err = DB_SUCCESS;
+	} else {
 		ulint		len;
 		const byte*	field;
 		mem_heap_t*	heap = NULL;
@@ -2346,9 +2358,6 @@ row_import_set_sys_max_row_id(
 		if (heap != NULL) {
 			mem_heap_free(heap);
 		}
-	} else {
-		/* The table is empty. */
-		err = DB_SUCCESS;
 	}
 
 	btr_pcur_close(&pcur);

storage/innobase/row/row0merge.cc

@@ -1856,6 +1856,13 @@ row_merge_read_clustered_index(
 
 	btr_pcur_open_at_index_side(
 		true, clust_index, BTR_SEARCH_LEAF, &pcur, true, 0, &mtr);
+	if (rec_is_default_row(btr_pcur_get_rec(&pcur), clust_index)) {
+		ut_ad(btr_pcur_is_on_user_rec(&pcur));
+		/* Skip the 'default row' pseudo-record. */
+		btr_pcur_move_to_next_user_rec(&pcur, &mtr);
+	} else {
+		ut_ad(!clust_index->is_instant());
+	}
 
 	if (old_table != new_table) {
 		/* The table is being rebuilt.  Identify the columns

storage/innobase/row/row0sel.cc

@@ -1492,6 +1492,15 @@ row_sel_try_search_shortcut(
 		return(SEL_RETRY);
 	}
 
+	if (rec_is_default_row(rec, index)) {
+		/* Skip the 'default row' pseudo-record. */
+		if (!btr_pcur_move_to_next_user_rec(&plan->pcur, mtr)) {
+			return(SEL_RETRY);
+		}
+
+		rec = btr_pcur_get_rec(&plan->pcur);
+	}
+
 	ut_ad(plan->mode == PAGE_CUR_GE);
 
 	/* As the cursor is now placed on a user record after a search with
@@ -1819,6 +1828,12 @@ row_sel(
 		goto next_rec;
 	}
 
+	if (rec_is_default_row(rec, index)) {
+		/* Skip the 'default row' pseudo-record. */
+		cost_counter++;
+		goto next_rec;
+	}
+
 	if (!consistent_read) {
 		/* Try to place a lock on the index record */
 		ulint	lock_type;
@@ -3597,7 +3612,13 @@ sel_restore_position_for_mysql(
 	case BTR_PCUR_ON:
 		if (!success && moves_up) {
 next:
-			btr_pcur_move_to_next(pcur, mtr);
+			if (btr_pcur_move_to_next(pcur, mtr)
+			    && rec_is_default_row(
+				    btr_pcur_get_rec(pcur),
+				    pcur->btr_cur.page_cur.index)) {
+				btr_pcur_move_to_next(pcur, mtr);
+			}
+
 			return(TRUE);
 		}
 		return(!success);
@@ -3608,7 +3629,9 @@ sel_restore_position_for_mysql(
 		/* positioned to record after pcur->old_rec. */
 		pcur->pos_state = BTR_PCUR_IS_POSITIONED;
 prev:
-		if (btr_pcur_is_on_user_rec(pcur) && !moves_up) {
+		if (btr_pcur_is_on_user_rec(pcur) && !moves_up
+		    && !rec_is_default_row(btr_pcur_get_rec(pcur),
+					   pcur->btr_cur.page_cur.index)) {
 			btr_pcur_move_to_prev(pcur, mtr);
 		}
 		return(TRUE);
@@ -4716,12 +4739,24 @@ row_search_mvcc(
 	corruption */
 
 	if (comp) {
+		if (rec_get_info_bits(rec, true) & REC_INFO_MIN_REC_FLAG) {
+			/* Skip the 'default row' pseudo-record. */
+			ut_ad(index->is_instant());
+			goto next_rec;
+		}
+
 		next_offs = rec_get_next_offs(rec, TRUE);
 		if (UNIV_UNLIKELY(next_offs < PAGE_NEW_SUPREMUM)) {
 
 			goto wrong_offs;
 		}
 	} else {
+		if (rec_get_info_bits(rec, false) & REC_INFO_MIN_REC_FLAG) {
+			/* Skip the 'default row' pseudo-record. */
+			ut_ad(index->is_instant());
+			goto next_rec;
+		}
+
 		next_offs = rec_get_next_offs(rec, FALSE);
 		if (UNIV_UNLIKELY(next_offs < PAGE_OLD_SUPREMUM)) {
 
@@ -5993,6 +6028,9 @@ row_search_get_max_rec(
 
 	btr_pcur_close(&pcur);
 
+	ut_ad(!rec
+	      || !(rec_get_info_bits(rec, dict_table_is_comp(index->table))
+		   & (REC_INFO_MIN_REC_FLAG | REC_INFO_DELETED_FLAG)));
 	return(rec);
 }