From 92e3657d85b13355563ba4c447ddf89fcb4c4b3e Mon Sep 17 00:00:00 2001 From: Ayush Tiwari Date: Sat, 7 Mar 2026 18:27:36 +0000 Subject: [PATCH v2] Add tid_block() and tid_offset() accessor functions Add two new built-in SQL functions to extract the components of a tid (tuple identifier) value: tid_block(tid) -> bigint -- extract block number tid_offset(tid) -> integer -- extract offset number These provide a clean, efficient alternative to the common workaround of ctid::text::point for decomposing TID values. The text-based hack is fragile, inefficient, and unavailable outside of SQL contexts. tid_block() returns int8 (bigint) because BlockNumber is uint32, which exceeds the range of int4. tid_offset() returns int4 (integer) because OffsetNumber is uint16, which fits safely in int4. Both functions use the NoCheck accessor variants from itemptr.h, are marked leakproof, and include regression tests covering typical values, boundary conditions, NULL handling, and round-trip identity. --- doc/src/sgml/func/allfiles.sgml | 1 + doc/src/sgml/func/func-tid.sgml | 73 ++++++++++++++++++++++++ doc/src/sgml/func/func.sgml | 1 + src/backend/utils/adt/tid.c | 31 ++++++++++ src/include/catalog/pg_proc.dat | 6 ++ src/test/regress/expected/opr_sanity.out | 2 + src/test/regress/expected/tid.out | 66 +++++++++++++++++++++ src/test/regress/sql/tid.sql | 21 +++++++ 8 files changed, 201 insertions(+) create mode 100644 doc/src/sgml/func/func-tid.sgml diff --git a/doc/src/sgml/func/allfiles.sgml b/doc/src/sgml/func/allfiles.sgml index ce11ef1d5d8..f5e3f008537 100644 --- a/doc/src/sgml/func/allfiles.sgml +++ b/doc/src/sgml/func/allfiles.sgml @@ -17,6 +17,7 @@ Complete list of usable sgml source files in this directory. + diff --git a/doc/src/sgml/func/func-tid.sgml b/doc/src/sgml/func/func-tid.sgml new file mode 100644 index 00000000000..6b3de14d093 --- /dev/null +++ b/doc/src/sgml/func/func-tid.sgml @@ -0,0 +1,73 @@ + + TID Functions + + + TID + functions + + + + tid_block + + + + tid_offset + + + + For the tid data type (described in ), + shows the functions available for extracting the block number and + tuple offset. These functions are commonly used with the + ctid system column. + + + + <type>TID</type> Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + tid_block ( tid ) + bigint + + + Extracts the block number from a tuple identifier. + + + tid_block('(42,7)'::tid) + 42 + + + + + + tid_offset ( tid ) + integer + + + Extracts the tuple offset within the block from a tuple identifier. + + + tid_offset('(42,7)'::tid) + 7 + + + + +
+ \ No newline at end of file diff --git a/doc/src/sgml/func/func.sgml b/doc/src/sgml/func/func.sgml index f351ef53f63..3fd21568b2e 100644 --- a/doc/src/sgml/func/func.sgml +++ b/doc/src/sgml/func/func.sgml @@ -59,6 +59,7 @@ repeat('Pg', 4) PgPgPgPg &func-formatting; &func-datetime; &func-enum; +&func-tid; &func-geometry; &func-net; &func-textsearch; diff --git a/src/backend/utils/adt/tid.c b/src/backend/utils/adt/tid.c index 07248b69e57..d13c7cbe418 100644 --- a/src/backend/utils/adt/tid.c +++ b/src/backend/utils/adt/tid.c @@ -280,6 +280,37 @@ hashtidextended(PG_FUNCTION_ARGS) } +/* + * TID accessor functions + */ + +/* + * tid_block - extract the block number from a TID + * + * Returns int8 because BlockNumber is uint32, which exceeds the range of int4. + */ +Datum +tid_block(PG_FUNCTION_ARGS) +{ + ItemPointer tid = PG_GETARG_ITEMPOINTER(0); + + PG_RETURN_INT64((int64) ItemPointerGetBlockNumberNoCheck(tid)); +} + +/* + * tid_offset - extract the offset number from a TID + * + * Returns int4 because OffsetNumber is uint16, which fits in int4. + */ +Datum +tid_offset(PG_FUNCTION_ARGS) +{ + ItemPointer tid = PG_GETARG_ITEMPOINTER(0); + + PG_RETURN_INT32((int32) ItemPointerGetOffsetNumberNoCheck(tid)); +} + + /* * Functions to get latest tid of a specified tuple. * diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index 361e2cfffeb..08267dd4f81 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -2750,6 +2750,12 @@ { oid => '2796', descr => 'smaller of two', proname => 'tidsmaller', prorettype => 'tid', proargtypes => 'tid tid', prosrc => 'tidsmaller' }, +{ oid => '9951', descr => 'extract block number from tid', + proname => 'tid_block', proleakproof => 't', prorettype => 'int8', + proargtypes => 'tid', prosrc => 'tid_block' }, +{ oid => '9952', descr => 'extract offset number from tid', + proname => 'tid_offset', proleakproof => 't', prorettype => 'int4', + proargtypes => 'tid', prosrc => 'tid_offset' }, { oid => '2233', descr => 'hash', proname => 'hashtid', prorettype => 'int4', proargtypes => 'tid', prosrc => 'hashtid' }, diff --git a/src/test/regress/expected/opr_sanity.out b/src/test/regress/expected/opr_sanity.out index 6ff4d7ee901..cfdc6b1a17a 100644 --- a/src/test/regress/expected/opr_sanity.out +++ b/src/test/regress/expected/opr_sanity.out @@ -887,6 +887,8 @@ oid8le(oid8,oid8) oid8gt(oid8,oid8) oid8ge(oid8,oid8) btoid8cmp(oid8,oid8) +tid_block(tid) +tid_offset(tid) -- Check that functions without argument are not marked as leakproof. SELECT p1.oid::regprocedure FROM pg_proc p1 JOIN pg_namespace pn diff --git a/src/test/regress/expected/tid.out b/src/test/regress/expected/tid.out index 083c83a1e1b..3497a77688b 100644 --- a/src/test/regress/expected/tid.out +++ b/src/test/regress/expected/tid.out @@ -42,6 +42,57 @@ SELECT * FROM pg_input_error_info('(0,-1)', 'tid'); invalid input syntax for type tid: "(0,-1)" | | | 22P02 (1 row) +-- tests for tid_block() and tid_offset() +SELECT tid_block('(0,0)'::tid), tid_offset('(0,0)'::tid); + tid_block | tid_offset +-----------+------------ + 0 | 0 +(1 row) + +SELECT tid_block('(0,1)'::tid), tid_offset('(0,1)'::tid); + tid_block | tid_offset +-----------+------------ + 0 | 1 +(1 row) + +SELECT tid_block('(42,7)'::tid), tid_offset('(42,7)'::tid); + tid_block | tid_offset +-----------+------------ + 42 | 7 +(1 row) + +-- max values: blockno uint32 max, offset uint16 max +SELECT tid_block('(4294967295,65535)'::tid), tid_offset('(4294967295,65535)'::tid); + tid_block | tid_offset +------------+------------ + 4294967295 | 65535 +(1 row) + +-- (-1,0) wraps to blockno 4294967295 +SELECT tid_block('(-1,0)'::tid); + tid_block +------------ + 4294967295 +(1 row) + +-- NULL handling (strict functions) +SELECT tid_block(NULL::tid), tid_offset(NULL::tid); + tid_block | tid_offset +-----------+------------ + | +(1 row) + +-- round-trip: blockno + offset reconstruct the original TID +SELECT t, tid_block(t), tid_offset(t), + format('(%s,%s)', tid_block(t), tid_offset(t))::tid = t AS roundtrip_ok +FROM (VALUES ('(0,0)'::tid), ('(1,42)'::tid), ('(4294967295,65535)'::tid)) AS v(t); + t | tid_block | tid_offset | roundtrip_ok +--------------------+------------+------------+-------------- + (0,0) | 0 | 0 | t + (1,42) | 1 | 42 | t + (4294967295,65535) | 4294967295 | 65535 | t +(3 rows) + -- tests for functions related to TID handling CREATE TABLE tid_tab (a int); -- min() and max() for TIDs @@ -58,6 +109,21 @@ SELECT max(ctid) FROM tid_tab; (0,2) (1 row) +-- tid_block() and tid_offset() with real table ctid +SELECT ctid, tid_block(ctid), tid_offset(ctid) FROM tid_tab; + ctid | tid_block | tid_offset +-------+-----------+------------ + (0,1) | 0 | 1 + (0,2) | 0 | 2 +(2 rows) + +-- use in WHERE clause +SELECT ctid FROM tid_tab WHERE tid_block(ctid) = 0 AND tid_offset(ctid) = 1; + ctid +------- + (0,1) +(1 row) + TRUNCATE tid_tab; -- Tests for currtid2() with various relation kinds -- Materialized view diff --git a/src/test/regress/sql/tid.sql b/src/test/regress/sql/tid.sql index 2602e20eb5a..c0a70be5cbd 100644 --- a/src/test/regress/sql/tid.sql +++ b/src/test/regress/sql/tid.sql @@ -16,6 +16,22 @@ SELECT pg_input_is_valid('(0,-1)', 'tid'); SELECT * FROM pg_input_error_info('(0,-1)', 'tid'); +-- tests for tid_block() and tid_offset() +SELECT tid_block('(0,0)'::tid), tid_offset('(0,0)'::tid); +SELECT tid_block('(0,1)'::tid), tid_offset('(0,1)'::tid); +SELECT tid_block('(42,7)'::tid), tid_offset('(42,7)'::tid); +-- max values: blockno uint32 max, offset uint16 max +SELECT tid_block('(4294967295,65535)'::tid), tid_offset('(4294967295,65535)'::tid); +-- (-1,0) wraps to blockno 4294967295 +SELECT tid_block('(-1,0)'::tid); +-- NULL handling (strict functions) +SELECT tid_block(NULL::tid), tid_offset(NULL::tid); +-- round-trip: blockno + offset reconstruct the original TID +SELECT t, tid_block(t), tid_offset(t), + format('(%s,%s)', tid_block(t), tid_offset(t))::tid = t AS roundtrip_ok +FROM (VALUES ('(0,0)'::tid), ('(1,42)'::tid), ('(4294967295,65535)'::tid)) AS v(t); + + -- tests for functions related to TID handling CREATE TABLE tid_tab (a int); @@ -24,6 +40,11 @@ CREATE TABLE tid_tab (a int); INSERT INTO tid_tab VALUES (1), (2); SELECT min(ctid) FROM tid_tab; SELECT max(ctid) FROM tid_tab; + +-- tid_block() and tid_offset() with real table ctid +SELECT ctid, tid_block(ctid), tid_offset(ctid) FROM tid_tab; +-- use in WHERE clause +SELECT ctid FROM tid_tab WHERE tid_block(ctid) = 0 AND tid_offset(ctid) = 1; TRUNCATE tid_tab; -- Tests for currtid2() with various relation kinds -- 2.43.0