On Sun, 31 Jul 2022 at 18:00, Hamid Akhtar <hamid.akh...@gmail.com> wrote:
>
>
> On Thu, 28 Jul 2022 at 00:36, Tom Lane <t...@sss.pgh.pa.us> wrote:
>
>> Hamid Akhtar <hamid.akh...@gmail.com> writes:
>> > That attached patch is based on the master branch. It makes the
>> following
>> > changes to the pageinspect contrib module:
>> > - Updates bt_page_stats_internal function to accept 3 arguments instead
>> of
>> > 2.
>> > - The function now uses SRF macros to return a set rather than a single
>> > row. The function call now requires specifying column names.
>>
>> FWIW, I think you'd be way better off changing the function name, say
>> to bt_multi_page_stats(). Overloading the name this way is going to
>> lead to great confusion, e.g. somebody who fat-fingers the number of
>> output arguments in a JDBC call could see confusing results due to
>> invoking the wrong one of the two functions. Also, I'm not quite sure
>> what you mean by "The function call now requires specifying column
>> names", but it doesn't sound like an acceptable restriction from a
>> compatibility standpoint. If a different name dodges that issue then
>> it's clearly a better way.
>>
>> regards, tom lane
>>
>
> Attached please find the latest version of the patch;
> pageinspect_btree_multipagestats_02.patch.
>
> It no longer modifies the existing bt_page_stats function. Instead, it
> introduces a new function bt_multi_page_stats as you had suggested. The
> function expects three arguments where the first argument is the index name
> followed by block number and number of blocks to be returned.
>
> Please ignore this statement. It was a typo.
> "The function call now requires specifying column names"
>
Attached is the rebased version of the patch
(pageinspect_btree_multipagestats_03.patch) for the master branch.
>
>
diff --git a/contrib/pageinspect/Makefile b/contrib/pageinspect/Makefile
index 5c07365..31d7b1c 100644
--- a/contrib/pageinspect/Makefile
+++ b/contrib/pageinspect/Makefile
@@ -13,12 +13,12 @@ OBJS = \
rawpage.o
EXTENSION = pageinspect
-DATA = pageinspect--1.9--1.10.sql pageinspect--1.8--1.9.sql \
- pageinspect--1.7--1.8.sql pageinspect--1.6--1.7.sql \
- pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
- pageinspect--1.4--1.5.sql pageinspect--1.3--1.4.sql \
- pageinspect--1.2--1.3.sql pageinspect--1.1--1.2.sql \
- pageinspect--1.0--1.1.sql
+DATA = pageinspect--1.10--1.11.sql pageinspect--1.9--1.10.sql \
+ pageinspect--1.8--1.9.sql pageinspect--1.7--1.8.sql \
+ pageinspect--1.6--1.7.sql pageinspect--1.5.sql \
+ pageinspect--1.5--1.6.sql pageinspect--1.4--1.5.sql \
+ pageinspect--1.3--1.4.sql pageinspect--1.2--1.3.sql \
+ pageinspect--1.1--1.2.sql pageinspect--1.0--1.1.sql
PGFILEDESC = "pageinspect - functions to inspect contents of database pages"
REGRESS = page btree brin gin gist hash checksum oldextversions
diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index 9375d55..f7ec95c 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -46,6 +46,7 @@ PG_FUNCTION_INFO_V1(bt_page_items);
PG_FUNCTION_INFO_V1(bt_page_items_bytea);
PG_FUNCTION_INFO_V1(bt_page_stats_1_9);
PG_FUNCTION_INFO_V1(bt_page_stats);
+PG_FUNCTION_INFO_V1(bt_multi_page_stats);
#define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
#define IS_BTREE(r) ((r)->rd_rel->relam == BTREE_AM_OID)
@@ -80,6 +81,26 @@ typedef struct BTPageStat
BTCycleId btpo_cycleid;
} BTPageStat;
+/*
+ * cross-call data structure for SRF for page stats
+ */
+typedef struct ua_page_stats
+{
+ uint64 blkno;
+ uint64 blk_count;
+} ua_page_stats;
+
+/*
+ * cross-call data structure for SRF for page items
+ */
+typedef struct ua_page_items
+{
+ Page page;
+ OffsetNumber offset;
+ bool leafpage;
+ bool rightmost;
+ TupleDesc tupd;
+} ua_page_items;
/* -------------------------------------------------
* GetBTPageStatistics()
@@ -177,34 +198,15 @@ GetBTPageStatistics(BlockNumber blkno, Buffer buffer, BTPageStat *stat)
}
/* -----------------------------------------------
- * bt_page_stats()
+ * bt_index_block_validate()
*
- * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
+ * Validate index type is btree and block number
+ * is within a valid block number range.
* -----------------------------------------------
*/
-static Datum
-bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+static void
+bt_index_block_validate(Relation rel, int64 blkno)
{
- text *relname = PG_GETARG_TEXT_PP(0);
- int64 blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
- Buffer buffer;
- Relation rel;
- RangeVar *relrv;
- Datum result;
- HeapTuple tuple;
- TupleDesc tupleDesc;
- int j;
- char *values[11];
- BTPageStat stat;
-
- if (!superuser())
- ereport(ERROR,
- (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
- errmsg("must be superuser to use pageinspect functions")));
-
- relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
- rel = relation_openrv(relrv, AccessShareLock);
-
if (!IS_INDEX(rel) || !IS_BTREE(rel))
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -232,6 +234,38 @@ bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
errmsg("block 0 is a meta page")));
CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+}
+
+/* -----------------------------------------------
+ * bt_page_stats()
+ *
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
+ * -----------------------------------------------
+ */
+static Datum
+bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+{
+ text *relname = PG_GETARG_TEXT_PP(0);
+ int64 blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
+ Buffer buffer;
+ Relation rel;
+ RangeVar *relrv;
+ Datum result;
+ HeapTuple tuple;
+ TupleDesc tupleDesc;
+ int j;
+ char *values[11];
+ BTPageStat stat;
+
+ if (!superuser())
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ errmsg("must be superuser to use pageinspect functions")));
+
+ relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+ rel = relation_openrv(relrv, AccessShareLock);
+
+ bt_index_block_validate(rel, blkno);
buffer = ReadBuffer(rel, blkno);
LockBuffer(buffer, BUFFER_LOCK_SHARE);
@@ -270,6 +304,134 @@ bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
PG_RETURN_DATUM(result);
}
+/* -----------------------------------------------
+ * bt_multi_page_stats()
+ *
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1, 1);
+ * Where the first argument is the name followed
+ * by block number and number of blocks to be
+ * returned.
+ * -----------------------------------------------
+ */
+Datum
+bt_multi_page_stats(PG_FUNCTION_ARGS)
+{
+ text *relname = PG_GETARG_TEXT_PP(0);
+ int64 blkno = PG_GETARG_INT64(1);
+ int64 blk_count = PG_GETARG_INT64(2);
+ RangeVar *relrv;
+ Relation rel;
+ ua_page_stats *uargs;
+ FuncCallContext *fctx;
+ MemoryContext mctx;
+
+ if (!superuser())
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ errmsg("must be superuser to use pageinspect functions")));
+
+ if (SRF_IS_FIRSTCALL())
+ {
+ fctx = SRF_FIRSTCALL_INIT();
+
+ relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+ rel = relation_openrv(relrv, AccessShareLock);
+
+ /*
+ * Check if relaion is a valid btree index and block number is within
+ * the valid range.
+ */
+ bt_index_block_validate(rel, blkno);
+
+ relation_close(rel, AccessShareLock);
+
+ mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
+
+ uargs = palloc(sizeof(struct ua_page_stats));
+
+ /*
+ * Set the start block number and the total number of blocks to ne
+ * retrieved.
+ */
+ uargs->blkno = blkno;
+ uargs->blk_count = blk_count;
+
+ fctx->user_fctx = uargs;
+
+ MemoryContextSwitchTo(mctx);
+ }
+
+ fctx = SRF_PERCALL_SETUP();
+ uargs = fctx->user_fctx;
+
+ /* We need to fetch next block statistics */
+ if (uargs->blk_count > 0)
+ {
+ Buffer buffer;
+ Datum result;
+ HeapTuple tuple;
+ int j;
+ char *values[11];
+ BTPageStat stat;
+ TupleDesc tupleDesc;
+
+ relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+ rel = relation_openrv(relrv, AccessShareLock);
+
+ /*
+ * Since index may have changed between function calls, double check
+ * that we are still within the vaild range.
+ */
+ CHECK_RELATION_BLOCK_RANGE(rel, uargs->blkno);
+
+ buffer = ReadBuffer(rel, uargs->blkno);
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+ /* keep compiler quiet */
+ stat.btpo_prev = stat.btpo_next = InvalidBlockNumber;
+ stat.btpo_flags = stat.free_size = stat.avg_item_size = 0;
+
+ GetBTPageStatistics(uargs->blkno, buffer, &stat);
+
+ UnlockReleaseBuffer(buffer);
+ relation_close(rel, AccessShareLock);
+
+ /* 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");
+
+ j = 0;
+ values[j++] = psprintf("%u", stat.blkno);
+ values[j++] = psprintf("%c", stat.type);
+ values[j++] = psprintf("%u", stat.live_items);
+ values[j++] = psprintf("%u", stat.dead_items);
+ values[j++] = psprintf("%u", stat.avg_item_size);
+ values[j++] = psprintf("%u", stat.page_size);
+ values[j++] = psprintf("%u", stat.free_size);
+ values[j++] = psprintf("%u", stat.btpo_prev);
+ values[j++] = psprintf("%u", stat.btpo_next);
+ values[j++] = psprintf("%u", stat.btpo_level);
+ values[j++] = psprintf("%d", stat.btpo_flags);
+
+ /* Constructu tuple to be returned */
+ tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
+ values);
+
+ result = HeapTupleGetDatum(tuple);
+
+ /*
+ * Move to the next block number and decrement the number of blocks
+ * still to be fetched
+ */
+ uargs->blkno++;
+ uargs->blk_count--;
+
+ SRF_RETURN_NEXT(fctx, result);
+ }
+
+ SRF_RETURN_DONE(fctx);
+}
+
Datum
bt_page_stats_1_9(PG_FUNCTION_ARGS)
{
@@ -283,19 +445,6 @@ bt_page_stats(PG_FUNCTION_ARGS)
return bt_page_stats_internal(fcinfo, PAGEINSPECT_V1_8);
}
-
-/*
- * cross-call data structure for SRF
- */
-struct user_args
-{
- Page page;
- OffsetNumber offset;
- bool leafpage;
- bool rightmost;
- TupleDesc tupd;
-};
-
/*-------------------------------------------------------
* bt_page_print_tuples()
*
@@ -303,7 +452,7 @@ struct user_args
* ------------------------------------------------------
*/
static Datum
-bt_page_print_tuples(struct user_args *uargs)
+bt_page_print_tuples(struct ua_page_items *uargs)
{
Page page = uargs->page;
OffsetNumber offset = uargs->offset;
@@ -453,7 +602,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
Datum result;
FuncCallContext *fctx;
MemoryContext mctx;
- struct user_args *uargs;
+ struct ua_page_items *uargs;
if (!superuser())
ereport(ERROR,
@@ -473,33 +622,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
rel = relation_openrv(relrv, AccessShareLock);
- if (!IS_INDEX(rel) || !IS_BTREE(rel))
- ereport(ERROR,
- (errcode(ERRCODE_WRONG_OBJECT_TYPE),
- errmsg("\"%s\" is not a %s index",
- RelationGetRelationName(rel), "btree")));
-
- /*
- * Reject attempts to read non-local temporary relations; we would be
- * likely to get wrong data since we have no visibility into the
- * owning session's local buffers.
- */
- if (RELATION_IS_OTHER_TEMP(rel))
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot access temporary tables of other sessions")));
-
- if (blkno < 0 || blkno > MaxBlockNumber)
- ereport(ERROR,
- (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
- errmsg("invalid block number")));
-
- if (blkno == 0)
- ereport(ERROR,
- (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
- errmsg("block 0 is a meta page")));
-
- CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+ bt_index_block_validate(rel, blkno);
buffer = ReadBuffer(rel, blkno);
LockBuffer(buffer, BUFFER_LOCK_SHARE);
@@ -511,7 +634,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
*/
mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
- uargs = palloc(sizeof(struct user_args));
+ uargs = palloc(sizeof(struct ua_page_items));
uargs->page = palloc(BLCKSZ);
memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);
@@ -587,7 +710,7 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
bytea *raw_page = PG_GETARG_BYTEA_P(0);
Datum result;
FuncCallContext *fctx;
- struct user_args *uargs;
+ struct ua_page_items *uargs;
if (!superuser())
ereport(ERROR,
@@ -603,7 +726,7 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
fctx = SRF_FIRSTCALL_INIT();
mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
- uargs = palloc(sizeof(struct user_args));
+ uargs = palloc(sizeof(struct ua_page_items));
uargs->page = get_page_from_raw(raw_page);
diff --git a/contrib/pageinspect/expected/btree.out b/contrib/pageinspect/expected/btree.out
index 035a81a..383b9be 100644
--- a/contrib/pageinspect/expected/btree.out
+++ b/contrib/pageinspect/expected/btree.out
@@ -34,6 +34,117 @@ btpo_flags | 3
SELECT * FROM bt_page_stats('test1_a_idx', 2);
ERROR: block number out of range
+-- bt_multi_page_stats() function returns a set of records of page statistics.
+CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
+CREATE INDEX test2_col1_idx ON test2(col1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 0, 1);
+ERROR: block 0 is a meta page
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, -1);
+ERROR: block number out of range
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 0);
+(0 rows)
+
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 2);
+-[ RECORD 1 ]-+-----
+blkno | 1
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 0
+btpo_next | 2
+btpo_level | 0
+btpo_flags | 1
+-[ RECORD 2 ]-+-----
+blkno | 2
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 1
+btpo_next | 4
+btpo_level | 0
+btpo_flags | 1
+
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 2, 6);
+-[ RECORD 1 ]-+-----
+blkno | 2
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 1
+btpo_next | 4
+btpo_level | 0
+btpo_flags | 1
+-[ RECORD 2 ]-+-----
+blkno | 3
+type | r
+live_items | 14
+dead_items | 0
+avg_item_size | 15
+page_size | 8192
+free_size | 7876
+btpo_prev | 0
+btpo_next | 0
+btpo_level | 1
+btpo_flags | 2
+-[ RECORD 3 ]-+-----
+blkno | 4
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 2
+btpo_next | 5
+btpo_level | 0
+btpo_flags | 1
+-[ RECORD 4 ]-+-----
+blkno | 5
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 4
+btpo_next | 6
+btpo_level | 0
+btpo_flags | 1
+-[ RECORD 5 ]-+-----
+blkno | 6
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 5
+btpo_next | 7
+btpo_level | 0
+btpo_flags | 1
+-[ RECORD 6 ]-+-----
+blkno | 7
+type | l
+live_items | 367
+dead_items | 0
+avg_item_size | 16
+page_size | 8192
+free_size | 808
+btpo_prev | 6
+btpo_next | 8
+btpo_level | 0
+btpo_flags | 1
+
+DROP TABLE test2;
SELECT * FROM bt_page_items('test1_a_idx', -1);
ERROR: invalid block number
SELECT * FROM bt_page_items('test1_a_idx', 0);
diff --git a/contrib/pageinspect/pageinspect--1.10--1.11.sql b/contrib/pageinspect/pageinspect--1.10--1.11.sql
index e69de29..976d029 100644
--- a/contrib/pageinspect/pageinspect--1.10--1.11.sql
+++ b/contrib/pageinspect/pageinspect--1.10--1.11.sql
@@ -0,0 +1,23 @@
+/* contrib/pageinspect/pageinspect--1.10--1.11.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pageinspect UPDATE TO '1.11'" to load this file. \quit
+
+--
+-- bt_multi_page_stats()
+--
+CREATE FUNCTION bt_multi_page_stats(IN relname text, IN blkno int8, IN blk_count int8,
+ OUT blkno int8,
+ OUT type "char",
+ OUT live_items int4,
+ OUT dead_items int4,
+ OUT avg_item_size int4,
+ OUT page_size int4,
+ OUT free_size int4,
+ OUT btpo_prev int8,
+ OUT btpo_next int8,
+ OUT btpo_level int8,
+ OUT btpo_flags int4)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'bt_multi_page_stats'
+LANGUAGE C STRICT PARALLEL SAFE;
diff --git a/contrib/pageinspect/pageinspect.control b/contrib/pageinspect/pageinspect.control
index 7cdf379..f277413 100644
--- a/contrib/pageinspect/pageinspect.control
+++ b/contrib/pageinspect/pageinspect.control
@@ -1,5 +1,5 @@
# pageinspect extension
comment = 'inspect the contents of database pages at a low level'
-default_version = '1.10'
+default_version = '1.11'
module_pathname = '$libdir/pageinspect'
relocatable = true
diff --git a/contrib/pageinspect/sql/btree.sql b/contrib/pageinspect/sql/btree.sql
index 1f554f0..9a95914 100644
--- a/contrib/pageinspect/sql/btree.sql
+++ b/contrib/pageinspect/sql/btree.sql
@@ -11,6 +11,16 @@ SELECT * FROM bt_page_stats('test1_a_idx', 0);
SELECT * FROM bt_page_stats('test1_a_idx', 1);
SELECT * FROM bt_page_stats('test1_a_idx', 2);
+-- bt_multi_page_stats() function returns a set of records of page statistics.
+CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
+CREATE INDEX test2_col1_idx ON test2(col1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 0, 1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, -1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 0);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 2);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 2, 6);
+DROP TABLE test2;
+
SELECT * FROM bt_page_items('test1_a_idx', -1);
SELECT * FROM bt_page_items('test1_a_idx', 0);
SELECT * FROM bt_page_items('test1_a_idx', 1);
