From 9c08aea6a3090a396be334cc58c511edab05776a Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Tue, 29 Mar 2022 11:31:43 -0400 Subject: Add new block-by-block strategy for CREATE DATABASE. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Because this strategy logs changes on a block-by-block basis, it avoids the need to checkpoint before and after the operation. However, because it logs each changed block individually, it might generate a lot of extra write-ahead logging if the template database is large. Therefore, the older strategy remains available via a new STRATEGY parameter to CREATE DATABASE, and a corresponding --strategy option to createdb. Somewhat controversially, this patch assembles the list of relations to be copied to the new database by reading the pg_class relation of the template database. Cross-database access like this isn't normally possible, but it can be made to work here because there can't be any connections to the database being copied, nor can it contain any in-doubt transactions. Even so, we have to use lower-level interfaces than normal, since the table scan and relcache interfaces will not work for a database to which we're not connected. The advantage of this approach is that we do not need to rely on the filesystem to determine what ought to be copied, but instead on PostgreSQL's own knowledge of the database structure. This avoids, for example, copying stray files that happen to be located in the source database directory. Dilip Kumar, with a fairly large number of cosmetic changes by me. Reviewed and tested by Ashutosh Sharma, Andres Freund, John Naylor, Greg Nancarrow, Neha Sharma. Additional feedback from Bruce Momjian, Heikki Linnakangas, Julien Rouhaud, Adam Brusselback, Kyotaro Horiguchi, Tomas Vondra, Andrew Dunstan, Álvaro Herrera, and others. Discussion: http://postgr.es/m/CA+TgmoYtcdxBjLh31DLxUXHxFVMPGzrU5_T=CYCvRyFHywSBUQ@mail.gmail.com --- src/include/storage/bufmgr.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'src/include/storage/bufmgr.h') diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index dd01841c300..a6b657f0ba5 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -184,7 +184,8 @@ extern Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum, BufferAccessStrategy strategy); extern Buffer ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum, BlockNumber blockNum, - ReadBufferMode mode, BufferAccessStrategy strategy); + ReadBufferMode mode, BufferAccessStrategy strategy, + bool permanent); extern void ReleaseBuffer(Buffer buffer); extern void UnlockReleaseBuffer(Buffer buffer); extern void MarkBufferDirty(Buffer buffer); @@ -203,6 +204,9 @@ extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation, extern void FlushOneBuffer(Buffer buffer); extern void FlushRelationBuffers(Relation rel); extern void FlushRelationsAllBuffers(struct SMgrRelationData **smgrs, int nrels); +extern void CreateAndCopyRelationData(RelFileNode src_rnode, + RelFileNode dst_rnode, + bool permanent); extern void FlushDatabaseBuffers(Oid dbid); extern void DropRelFileNodeBuffers(struct SMgrRelationData *smgr_reln, ForkNumber *forkNum, int nforks, BlockNumber *firstDelBlock); -- cgit v1.2.3