pageinspect: Add bt_page_items function with bytea argument

Author: Tomas Vondra <[email protected]>
Reviewed-by: Ashutosh Sharma <[email protected]>

contrib/pageinspect/btreefuncs.c

@@ -41,6 +41,7 @@
 
 PG_FUNCTION_INFO_V1(bt_metap);
 PG_FUNCTION_INFO_V1(bt_page_items);
+PG_FUNCTION_INFO_V1(bt_page_items_bytea);
 PG_FUNCTION_INFO_V1(bt_page_stats);
 
 #define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
@@ -235,14 +236,6 @@ bt_page_stats(PG_FUNCTION_ARGS)
  PG_RETURN_DATUM(result);
 }
 
-/*-------------------------------------------------------
- * bt_page_items()
- *
- * Get IndexTupleData set in a btree page
- *
- * Usage: SELECT * FROM bt_page_items('t1_pkey', 1);
- *-------------------------------------------------------
- */
 
 /*
  * cross-call data structure for SRF
@@ -253,14 +246,72 @@ struct user_args
  OffsetNumber offset;
 };
 
+/*-------------------------------------------------------
+ * bt_page_print_tuples()
+ *
+ * Form a tuple describing index tuple at a given offset
+ * ------------------------------------------------------
+ */
+static Datum
+bt_page_print_tuples(FuncCallContext *fctx, Page page, OffsetNumber offset)
+{
+ char *values[6];
+ HeapTuple tuple;
+ ItemId id;
+ IndexTuple itup;
+ int j;
+ int off;
+ int dlen;
+ char *dump;
+ char *ptr;
+
+ id = PageGetItemId(page, offset);
+
+ if (!ItemIdIsValid(id))
+ elog(ERROR, "invalid ItemId");
+
+ itup = (IndexTuple) PageGetItem(page, id);
+
+ j = 0;
+ values[j++] = psprintf("%d", offset);
+ values[j++] = psprintf("(%u,%u)",
+ ItemPointerGetBlockNumberNoCheck(&itup->t_tid),
+ ItemPointerGetOffsetNumberNoCheck(&itup->t_tid));
+ values[j++] = psprintf("%d", (int) IndexTupleSize(itup));
+ values[j++] = psprintf("%c", IndexTupleHasNulls(itup) ? 't' : 'f');
+ values[j++] = psprintf("%c", IndexTupleHasVarwidths(itup) ? 't' : 'f');
+
+ ptr = (char *) itup + IndexInfoFindDataOffset(itup->t_info);
+ dlen = IndexTupleSize(itup) - IndexInfoFindDataOffset(itup->t_info);
+ dump = palloc0(dlen * 3 + 1);
+ values[j] = dump;
+ for (off = 0; off < dlen; off++)
+ {
+ if (off > 0)
+ *dump++ = ' ';
+ sprintf(dump, "%02x", *(ptr + off) & 0xff);
+ dump += 2;
+ }
+
+ tuple = BuildTupleFromCStrings(fctx->attinmeta, values);
+
+ return HeapTupleGetDatum(tuple);
+}
+
+/*-------------------------------------------------------
+ * bt_page_items()
+ *
+ * Get IndexTupleData set in a btree page
+ *
+ * Usage: SELECT * FROM bt_page_items('t1_pkey', 1);
+ *-------------------------------------------------------
+ */
 Datum
 bt_page_items(PG_FUNCTION_ARGS)
 {
  text *relname = PG_GETARG_TEXT_PP(0);
  uint32 blkno = PG_GETARG_UINT32(1);
  Datum result;
- char *values[6];
- HeapTuple tuple;
  FuncCallContext *fctx;
  MemoryContext mctx;
  struct user_args *uargs;
@@ -345,47 +396,8 @@ bt_page_items(PG_FUNCTION_ARGS)
 
  if (fctx->call_cntr < fctx->max_calls)
  {
- ItemId id;
- IndexTuple itup;
- int j;
- int off;
- int dlen;
- char *dump;
- char *ptr;
-
- id = PageGetItemId(uargs->page, uargs->offset);
-
- if (!ItemIdIsValid(id))
- elog(ERROR, "invalid ItemId");
-
- itup = (IndexTuple) PageGetItem(uargs->page, id);
-
- j = 0;
- values[j++] = psprintf("%d", uargs->offset);
- values[j++] = psprintf("(%u,%u)",
- ItemPointerGetBlockNumberNoCheck(&itup->t_tid),
- ItemPointerGetOffsetNumberNoCheck(&itup->t_tid));
- values[j++] = psprintf("%d", (int) IndexTupleSize(itup));
- values[j++] = psprintf("%c", IndexTupleHasNulls(itup) ? 't' : 'f');
- values[j++] = psprintf("%c", IndexTupleHasVarwidths(itup) ? 't' : 'f');
-
- ptr = (char *) itup + IndexInfoFindDataOffset(itup->t_info);
- dlen = IndexTupleSize(itup) - IndexInfoFindDataOffset(itup->t_info);
- dump = palloc0(dlen * 3 + 1);
- values[j] = dump;
- for (off = 0; off < dlen; off++)
- {
- if (off > 0)
- *dump++ = ' ';
- sprintf(dump, "%02x", *(ptr + off) & 0xff);
- dump += 2;
- }
-
- tuple = BuildTupleFromCStrings(fctx->attinmeta, values);
- result = HeapTupleGetDatum(tuple);
-
- uargs->offset = uargs->offset + 1;
-
+ result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
+ uargs->offset++;
  SRF_RETURN_NEXT(fctx, result);
  }
  else
@@ -396,6 +408,90 @@ bt_page_items(PG_FUNCTION_ARGS)
  }
 }
 
+/*-------------------------------------------------------
+ * bt_page_items_bytea()
+ *
+ * Get IndexTupleData set in a btree page
+ *
+ * Usage: SELECT * FROM bt_page_items(get_raw_page('t1_pkey', 1));
+ *-------------------------------------------------------
+ */
+
+Datum
+bt_page_items_bytea(PG_FUNCTION_ARGS)
+{
+ bytea *raw_page = PG_GETARG_BYTEA_P(0);
+ Datum result;
+ FuncCallContext *fctx;
+ struct user_args *uargs;
+ int raw_page_size;
+
+ if (!superuser())
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ (errmsg("must be superuser to use pageinspect functions"))));
+
+ if (SRF_IS_FIRSTCALL())
+ {
+ BTPageOpaque opaque;
+ MemoryContext mctx;
+ TupleDesc tupleDesc;
+
+ raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
+
+ if (raw_page_size < SizeOfPageHeaderData)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("input page too small (%d bytes)", raw_page_size)));
+
+ fctx = SRF_FIRSTCALL_INIT();
+ mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
+
+ uargs = palloc(sizeof(struct user_args));
+
+ uargs->page = VARDATA(raw_page);
+
+ uargs->offset = FirstOffsetNumber;
+
+ opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);
+
+ if (P_ISMETA(opaque))
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("block is a meta page")));
+
+ if (P_ISDELETED(opaque))
+ elog(NOTICE, "page is deleted");
+
+ fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);
+
+ /* Build a tuple descriptor for our result type */
+ if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
+ elog(ERROR, "return type must be a row type");
+
+ fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);
+
+ fctx->user_fctx = uargs;
+
+ MemoryContextSwitchTo(mctx);
+ }
+
+ fctx = SRF_PERCALL_SETUP();
+ uargs = fctx->user_fctx;
+
+ if (fctx->call_cntr < fctx->max_calls)
+ {
+ result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
+ uargs->offset++;
+ SRF_RETURN_NEXT(fctx, result);
+ }
+ else
+ {
+ pfree(uargs);
+ SRF_RETURN_DONE(fctx);
+ }
+}
+
 
 /* ------------------------------------------------
  * bt_metap()

contrib/pageinspect/expected/btree.out

@@ -42,4 +42,17 @@ data | 01 00 00 00 00 00 00 01
 
 SELECT * FROM bt_page_items('test1_a_idx', 2);
 ERROR: block number out of range
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 0));
+ERROR: block is a meta page
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 1));
+-[ RECORD 1 ]-----------------------
+itemoffset | 1
+ctid | (0,1)
+itemlen | 16
+nulls | f
+vars | f
+data | 01 00 00 00 00 00 00 01
+
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 2));
+ERROR: block number 2 is out of range for relation "test1_a_idx"
 DROP TABLE test1;

contrib/pageinspect/pageinspect--1.5--1.6.sql

@@ -83,3 +83,17 @@ CREATE FUNCTION page_checksum(IN page bytea, IN blkno int4)
 RETURNS smallint
 AS 'MODULE_PATHNAME', 'page_checksum'
 LANGUAGE C STRICT PARALLEL SAFE;
+
+--
+-- bt_page_items_bytea()
+--
+CREATE FUNCTION bt_page_items(IN page bytea,
+ OUT itemoffset smallint,
+ OUT ctid tid,
+ OUT itemlen smallint,
+ OUT nulls bool,
+ OUT vars bool,
+ OUT data text)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'bt_page_items_bytea'
+LANGUAGE C STRICT PARALLEL SAFE;

contrib/pageinspect/sql/btree.sql

@@ -14,4 +14,8 @@ SELECT * FROM bt_page_items('test1_a_idx', 0);
 SELECT * FROM bt_page_items('test1_a_idx', 1);
 SELECT * FROM bt_page_items('test1_a_idx', 2);
 
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 0));
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 1));
+SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 2));
+
 DROP TABLE test1;

doc/src/sgml/pageinspect.sgml

@@ -333,6 +333,38 @@ test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1);
  </para>
  </listitem>
  </varlistentry>
+
+ <varlistentry>
+ <term>
+ <function>bt_page_items(page bytea) returns setof record</function>
+ <indexterm>
+ <primary>bt_page_items</primary>
+ </indexterm>
+ </term>
+
+ <listitem>
+ <para>
+ It is also possible to pass a page to <function>bt_page_items</function>
+ as a <type>bytea</> value. A page image obtained
+ with <function>get_raw_page</function> should be passed as argument. So
+ the last example could also be rewritten like this:
+<screen>
+test=# SELECT * FROM bt_page_items(get_raw_page('pg_cast_oid_index', 1));
+ itemoffset | ctid | itemlen | nulls | vars | data
+------------+---------+---------+-------+------+-------------
+ 1 | (0,1) | 12 | f | f | 23 27 00 00
+ 2 | (0,2) | 12 | f | f | 24 27 00 00
+ 3 | (0,3) | 12 | f | f | 25 27 00 00
+ 4 | (0,4) | 12 | f | f | 26 27 00 00
+ 5 | (0,5) | 12 | f | f | 27 27 00 00
+ 6 | (0,6) | 12 | f | f | 28 27 00 00
+ 7 | (0,7) | 12 | f | f | 29 27 00 00
+ 8 | (0,8) | 12 | f | f | 2a 27 00 00
+</screen>
+ All the other details are the same as explained in the previous item.
+ </para>
+ </listitem>
+ </varlistentry>
  </variablelist>
  </sect2>
 

src/include/access/nbtree.h

@@ -176,6 +176,7 @@ typedef struct BTMetaPageData
 #define P_ISLEAF(opaque) ((opaque)->btpo_flags & BTP_LEAF)
 #define P_ISROOT(opaque) ((opaque)->btpo_flags & BTP_ROOT)
 #define P_ISDELETED(opaque) ((opaque)->btpo_flags & BTP_DELETED)
+#define P_ISMETA(opaque) ((opaque)->btpo_flags & BTP_META)
 #define P_ISHALFDEAD(opaque) ((opaque)->btpo_flags & BTP_HALF_DEAD)
 #define P_IGNORE(opaque) ((opaque)->btpo_flags & (BTP_DELETED|BTP_HALF_DEAD))
 #define P_HAS_GARBAGE(opaque) ((opaque)->btpo_flags & BTP_HAS_GARBAGE)