pg_walinspect: Add pg_get_wal_fpi_info()
This function is able to extract the full page images from a range of records, specified as of input arguments start_lsn and end_lsn. Like the other functions of this module, an error is returned if using LSNs that do not reflect real system values. All the FPIs stored in a single record are extracted. The module's version is bumped to 1.1. Author: Bharath Rupireddy Reviewed-by: Bertrand Drouvot Discussion: https://postgr.es/m/CALj2ACVCcvzd7WiWvD=6_7NBvVB_r6G0EGSxL4F8vosAi6Se4g@mail.gmail.com
This commit is contained in:
Michael Paquier
parent
16fd03e956
commit
c31cf1c03d
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@ -7,7 +7,7 @@ OBJS = \
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PGFILEDESC = "pg_walinspect - functions to inspect contents of PostgreSQL Write-Ahead Log"
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EXTENSION = pg_walinspect
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DATA = pg_walinspect--1.0.sql
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DATA = pg_walinspect--1.0.sql pg_walinspect--1.0--1.1.sql
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REGRESS = pg_walinspect
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@ -10,7 +10,7 @@ CREATE TABLE sample_tbl(col1 int, col2 int);
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SELECT pg_current_wal_lsn() AS wal_lsn1 \gset
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INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
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SELECT pg_current_wal_lsn() AS wal_lsn2 \gset
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INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
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INSERT INTO sample_tbl SELECT * FROM generate_series(3, 4);
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-- ===================================================================
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-- Tests for input validation
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-- ===================================================================
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@ -73,6 +73,23 @@ SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_records_info(:'wal_lsn1', :'wal_lsn2'
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t
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(1 row)
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-- ===================================================================
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-- Tests to get full page image (FPI) from WAL record
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-- ===================================================================
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SELECT pg_current_wal_lsn() AS wal_lsn3 \gset
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-- Force FPI on the next update.
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CHECKPOINT;
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-- Update table to generate an FPI.
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UPDATE sample_tbl SET col1 = col1 * 100 WHERE col1 = 1;
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SELECT pg_current_wal_lsn() AS wal_lsn4 \gset
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-- Check if we get FPI from WAL record.
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SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_fpi_info(:'wal_lsn3', :'wal_lsn4')
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WHERE relfilenode = :'sample_tbl_oid';
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ok
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----
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t
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(1 row)
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-- ===================================================================
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-- Tests for permissions
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-- ===================================================================
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@ -98,6 +115,13 @@ SELECT has_function_privilege('regress_pg_walinspect',
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f
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(1 row)
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- no
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has_function_privilege
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------------------------
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f
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(1 row)
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-- Functions accessible by users with role pg_read_server_files
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GRANT pg_read_server_files TO regress_pg_walinspect;
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SELECT has_function_privilege('regress_pg_walinspect',
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@ -121,6 +145,13 @@ SELECT has_function_privilege('regress_pg_walinspect',
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t
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(1 row)
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- yes
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has_function_privilege
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------------------------
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t
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(1 row)
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REVOKE pg_read_server_files FROM regress_pg_walinspect;
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-- Superuser can grant execute to other users
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GRANT EXECUTE ON FUNCTION pg_get_wal_record_info(pg_lsn)
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@ -129,6 +160,8 @@ GRANT EXECUTE ON FUNCTION pg_get_wal_records_info(pg_lsn, pg_lsn)
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TO regress_pg_walinspect;
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GRANT EXECUTE ON FUNCTION pg_get_wal_stats(pg_lsn, pg_lsn, boolean)
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TO regress_pg_walinspect;
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GRANT EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn)
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TO regress_pg_walinspect;
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_record_info(pg_lsn)', 'EXECUTE'); -- yes
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has_function_privilege
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@ -150,12 +183,21 @@ SELECT has_function_privilege('regress_pg_walinspect',
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t
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(1 row)
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- yes
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has_function_privilege
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------------------------
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t
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(1 row)
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REVOKE EXECUTE ON FUNCTION pg_get_wal_record_info(pg_lsn)
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FROM regress_pg_walinspect;
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REVOKE EXECUTE ON FUNCTION pg_get_wal_records_info(pg_lsn, pg_lsn)
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FROM regress_pg_walinspect;
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REVOKE EXECUTE ON FUNCTION pg_get_wal_stats(pg_lsn, pg_lsn, boolean)
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FROM regress_pg_walinspect;
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REVOKE EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn)
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FROM regress_pg_walinspect;
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-- ===================================================================
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-- Clean up
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-- ===================================================================
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@ -19,6 +19,7 @@ contrib_targets += pg_walinspect
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install_data(
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'pg_walinspect.control',
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'pg_walinspect--1.0.sql',
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'pg_walinspect--1.0--1.1.sql',
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kwargs: contrib_data_args,
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)
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@ -0,0 +1,24 @@
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/* contrib/pg_walinspect/pg_walinspect--1.0--1.1.sql */
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-- complain if script is sourced in psql, rather than via ALTER EXTENSION
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\echo Use "ALTER EXTENSION pg_walinspect UPDATE TO '1.1'" to load this file. \quit
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--
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-- pg_get_wal_fpi_info()
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--
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CREATE FUNCTION pg_get_wal_fpi_info(IN start_lsn pg_lsn,
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IN end_lsn pg_lsn,
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OUT lsn pg_lsn,
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OUT reltablespace oid,
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OUT reldatabase oid,
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OUT relfilenode oid,
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OUT relblocknumber int8,
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OUT forkname text,
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OUT fpi bytea
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)
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RETURNS SETOF record
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AS 'MODULE_PATHNAME', 'pg_get_wal_fpi_info'
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LANGUAGE C STRICT PARALLEL SAFE;
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REVOKE EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn) FROM PUBLIC;
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GRANT EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn) TO pg_read_server_files;
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@ -30,6 +30,7 @@
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PG_MODULE_MAGIC;
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PG_FUNCTION_INFO_V1(pg_get_wal_fpi_info);
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PG_FUNCTION_INFO_V1(pg_get_wal_record_info);
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PG_FUNCTION_INFO_V1(pg_get_wal_records_info);
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PG_FUNCTION_INFO_V1(pg_get_wal_records_info_till_end_of_wal);
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@ -55,6 +56,7 @@ static void FillXLogStatsRow(const char *name, uint64 n, uint64 total_count,
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Datum *values, bool *nulls, uint32 ncols);
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static void GetWalStats(FunctionCallInfo fcinfo, XLogRecPtr start_lsn,
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XLogRecPtr end_lsn, bool stats_per_record);
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static void GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record);
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/*
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* Check if the given LSN is in future. Also, return the LSN up to which the
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@ -217,6 +219,115 @@ GetWALRecordInfo(XLogReaderState *record, Datum *values,
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Assert(i == ncols);
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}
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/*
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* Store a set of full page images from a single record.
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*/
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static void
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GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record)
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{
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#define PG_GET_WAL_FPI_INFO_COLS 7
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int block_id;
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ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
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for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
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{
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PGAlignedBlock buf;
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Page page;
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bytea *raw_page;
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BlockNumber blk;
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RelFileLocator rnode;
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ForkNumber fork;
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Datum values[PG_GET_WAL_FPI_INFO_COLS] = {0};
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bool nulls[PG_GET_WAL_FPI_INFO_COLS] = {0};
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int i = 0;
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if (!XLogRecHasBlockRef(record, block_id))
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continue;
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if (!XLogRecHasBlockImage(record, block_id))
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continue;
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page = (Page) buf.data;
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if (!RestoreBlockImage(record, block_id, page))
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ereport(ERROR,
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(errcode(ERRCODE_INTERNAL_ERROR),
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errmsg_internal("%s", record->errormsg_buf)));
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/* Full page exists, so let's save it. */
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(void) XLogRecGetBlockTagExtended(record, block_id,
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&rnode, &fork, &blk, NULL);
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values[i++] = LSNGetDatum(record->ReadRecPtr);
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values[i++] = ObjectIdGetDatum(rnode.spcOid);
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values[i++] = ObjectIdGetDatum(rnode.dbOid);
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values[i++] = ObjectIdGetDatum(rnode.relNumber);
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values[i++] = Int64GetDatum((int64) blk);
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if (fork >= 0 && fork <= MAX_FORKNUM)
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values[i++] = CStringGetTextDatum(forkNames[fork]);
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else
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ereport(ERROR,
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(errcode(ERRCODE_INTERNAL_ERROR),
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errmsg_internal("invalid fork number: %u", fork)));
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/* Initialize bytea buffer to copy the FPI to. */
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raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
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SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
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/* Take a verbatim copy of the FPI. */
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memcpy(VARDATA(raw_page), page, BLCKSZ);
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values[i++] = PointerGetDatum(raw_page);
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Assert(i == PG_GET_WAL_FPI_INFO_COLS);
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tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
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values, nulls);
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}
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#undef PG_GET_WAL_FPI_INFO_COLS
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}
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/*
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* Get full page images with their relation information for all the WAL
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* records between start and end LSNs. Decompression is applied to the
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* blocks, if necessary.
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*
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* This function emits an error if a future start or end WAL LSN i.e. WAL LSN
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* the database system doesn't know about is specified.
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*/
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Datum
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pg_get_wal_fpi_info(PG_FUNCTION_ARGS)
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{
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XLogRecPtr start_lsn;
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XLogRecPtr end_lsn;
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XLogReaderState *xlogreader;
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start_lsn = PG_GETARG_LSN(0);
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end_lsn = PG_GETARG_LSN(1);
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end_lsn = ValidateInputLSNs(false, start_lsn, end_lsn);
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InitMaterializedSRF(fcinfo, 0);
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xlogreader = InitXLogReaderState(start_lsn);
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while (ReadNextXLogRecord(xlogreader) &&
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xlogreader->EndRecPtr <= end_lsn)
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{
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GetWALFPIInfo(fcinfo, xlogreader);
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CHECK_FOR_INTERRUPTS();
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}
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pfree(xlogreader->private_data);
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XLogReaderFree(xlogreader);
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PG_RETURN_VOID();
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}
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/*
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* Get WAL record info.
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*
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@ -1,5 +1,5 @@
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# pg_walinspect extension
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comment = 'functions to inspect contents of PostgreSQL Write-Ahead Log'
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default_version = '1.0'
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default_version = '1.1'
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module_pathname = '$libdir/pg_walinspect'
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relocatable = true
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@ -11,7 +11,7 @@ INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
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SELECT pg_current_wal_lsn() AS wal_lsn2 \gset
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INSERT INTO sample_tbl SELECT * FROM generate_series(1, 2);
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INSERT INTO sample_tbl SELECT * FROM generate_series(3, 4);
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-- ===================================================================
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-- Tests for input validation
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@ -52,6 +52,22 @@ SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_records_info(:'wal_lsn1', :'wal_lsn2'
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SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_records_info(:'wal_lsn1', :'wal_lsn2')
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WHERE resource_manager = 'Heap' AND record_type = 'INSERT';
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-- ===================================================================
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-- Tests to get full page image (FPI) from WAL record
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-- ===================================================================
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SELECT pg_current_wal_lsn() AS wal_lsn3 \gset
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-- Force FPI on the next update.
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CHECKPOINT;
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-- Update table to generate an FPI.
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UPDATE sample_tbl SET col1 = col1 * 100 WHERE col1 = 1;
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SELECT pg_current_wal_lsn() AS wal_lsn4 \gset
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-- Check if we get FPI from WAL record.
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SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_fpi_info(:'wal_lsn3', :'wal_lsn4')
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WHERE relfilenode = :'sample_tbl_oid';
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-- ===================================================================
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-- Tests for permissions
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-- ===================================================================
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@ -66,6 +82,9 @@ SELECT has_function_privilege('regress_pg_walinspect',
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_stats(pg_lsn, pg_lsn, boolean) ', 'EXECUTE'); -- no
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- no
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-- Functions accessible by users with role pg_read_server_files
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GRANT pg_read_server_files TO regress_pg_walinspect;
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@ -79,6 +98,9 @@ SELECT has_function_privilege('regress_pg_walinspect',
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_stats(pg_lsn, pg_lsn, boolean) ', 'EXECUTE'); -- yes
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- yes
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REVOKE pg_read_server_files FROM regress_pg_walinspect;
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-- Superuser can grant execute to other users
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@ -91,6 +113,9 @@ GRANT EXECUTE ON FUNCTION pg_get_wal_records_info(pg_lsn, pg_lsn)
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GRANT EXECUTE ON FUNCTION pg_get_wal_stats(pg_lsn, pg_lsn, boolean)
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TO regress_pg_walinspect;
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GRANT EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn)
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TO regress_pg_walinspect;
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_record_info(pg_lsn)', 'EXECUTE'); -- yes
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@ -100,6 +125,9 @@ SELECT has_function_privilege('regress_pg_walinspect',
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_stats(pg_lsn, pg_lsn, boolean) ', 'EXECUTE'); -- yes
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SELECT has_function_privilege('regress_pg_walinspect',
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'pg_get_wal_fpi_info(pg_lsn, pg_lsn) ', 'EXECUTE'); -- yes
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REVOKE EXECUTE ON FUNCTION pg_get_wal_record_info(pg_lsn)
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FROM regress_pg_walinspect;
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@ -109,6 +137,9 @@ REVOKE EXECUTE ON FUNCTION pg_get_wal_records_info(pg_lsn, pg_lsn)
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REVOKE EXECUTE ON FUNCTION pg_get_wal_stats(pg_lsn, pg_lsn, boolean)
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FROM regress_pg_walinspect;
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REVOKE EXECUTE ON FUNCTION pg_get_wal_fpi_info(pg_lsn, pg_lsn)
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FROM regress_pg_walinspect;
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-- ===================================================================
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-- Clean up
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-- ===================================================================
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@ -188,6 +188,38 @@ combined_size_percentage | 2.8634072910530795
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>pg_get_wal_fpi_info(start_lsn pg_lsn, end_lsn pg_lsn) returns setof record</function>
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</term>
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<listitem>
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<para>
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Gets a copy of full page images as <type>bytea</type> values (after
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applying decompression when necessary) and their information associated
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with all the valid WAL records between
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<replaceable>start_lsn</replaceable> and
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<replaceable>end_lsn</replaceable>. Returns one row per full page image.
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If <replaceable>start_lsn</replaceable> or
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<replaceable>end_lsn</replaceable> are not yet available, the function
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will raise an error. For example:
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<screen>
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postgres=# SELECT lsn, reltablespace, reldatabase, relfilenode, relblocknumber,
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forkname, substring(fpi for 24) as fpi_trimmed
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FROM pg_get_wal_fpi_info('0/1801690', '0/1825C60');
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-[ RECORD 1 ]--+---------------------------------------------------
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lsn | 0/1807E20
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reltablespace | 1663
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reldatabase | 5
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relfilenode | 16396
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relblocknumber | 43
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forkname | main
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fpi_trimmed | \x00000000b89e660100000000a003c0030020042000000000
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</screen>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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