diff options
Diffstat (limited to 'src/backend/storage/smgr/md.c')
| -rw-r--r-- | src/backend/storage/smgr/md.c | 128 |
1 files changed, 64 insertions, 64 deletions
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index e982a8dd7f7..3d955aa72b3 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -42,41 +42,41 @@ #include "utils/memutils.h" /* - * The magnetic disk storage manager keeps track of open file - * descriptors in its own descriptor pool. This is done to make it - * easier to support relations that are larger than the operating - * system's file size limit (often 2GBytes). In order to do that, - * we break relations up into "segment" files that are each shorter than - * the OS file size limit. The segment size is set by the RELSEG_SIZE - * configuration constant in pg_config.h. + * The magnetic disk storage manager keeps track of open file + * descriptors in its own descriptor pool. This is done to make it + * easier to support relations that are larger than the operating + * system's file size limit (often 2GBytes). In order to do that, + * we break relations up into "segment" files that are each shorter than + * the OS file size limit. The segment size is set by the RELSEG_SIZE + * configuration constant in pg_config.h. * - * On disk, a relation must consist of consecutively numbered segment - * files in the pattern - * -- Zero or more full segments of exactly RELSEG_SIZE blocks each - * -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks - * -- Optionally, any number of inactive segments of size 0 blocks. - * The full and partial segments are collectively the "active" segments. - * Inactive segments are those that once contained data but are currently - * not needed because of an mdtruncate() operation. The reason for leaving - * them present at size zero, rather than unlinking them, is that other - * backends and/or the checkpointer might be holding open file references to - * such segments. If the relation expands again after mdtruncate(), such - * that a deactivated segment becomes active again, it is important that - * such file references still be valid --- else data might get written - * out to an unlinked old copy of a segment file that will eventually - * disappear. + * On disk, a relation must consist of consecutively numbered segment + * files in the pattern + * -- Zero or more full segments of exactly RELSEG_SIZE blocks each + * -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks + * -- Optionally, any number of inactive segments of size 0 blocks. + * The full and partial segments are collectively the "active" segments. + * Inactive segments are those that once contained data but are currently + * not needed because of an mdtruncate() operation. The reason for leaving + * them present at size zero, rather than unlinking them, is that other + * backends and/or the checkpointer might be holding open file references to + * such segments. If the relation expands again after mdtruncate(), such + * that a deactivated segment becomes active again, it is important that + * such file references still be valid --- else data might get written + * out to an unlinked old copy of a segment file that will eventually + * disappear. * - * File descriptors are stored in the per-fork md_seg_fds arrays inside - * SMgrRelation. The length of these arrays is stored in md_num_open_segs. - * Note that a fork's md_num_open_segs having a specific value does not - * necessarily mean the relation doesn't have additional segments; we may - * just not have opened the next segment yet. (We could not have "all - * segments are in the array" as an invariant anyway, since another backend - * could extend the relation while we aren't looking.) We do not have - * entries for inactive segments, however; as soon as we find a partial - * segment, we assume that any subsequent segments are inactive. + * File descriptors are stored in the per-fork md_seg_fds arrays inside + * SMgrRelation. The length of these arrays is stored in md_num_open_segs. + * Note that a fork's md_num_open_segs having a specific value does not + * necessarily mean the relation doesn't have additional segments; we may + * just not have opened the next segment yet. (We could not have "all + * segments are in the array" as an invariant anyway, since another backend + * could extend the relation while we aren't looking.) We do not have + * entries for inactive segments, however; as soon as we find a partial + * segment, we assume that any subsequent segments are inactive. * - * The entire MdfdVec array is palloc'd in the MdCxt memory context. + * The entire MdfdVec array is palloc'd in the MdCxt memory context. */ typedef struct _MdfdVec @@ -154,7 +154,7 @@ _mdfd_open_flags(void) } /* - * mdinit() -- Initialize private state for magnetic disk storage manager. + * mdinit() -- Initialize private state for magnetic disk storage manager. */ void mdinit(void) @@ -165,7 +165,7 @@ mdinit(void) } /* - * mdexists() -- Does the physical file exist? + * mdexists() -- Does the physical file exist? * * Note: this will return true for lingering files, with pending deletions */ @@ -184,7 +184,7 @@ mdexists(SMgrRelation reln, ForkNumber forknum) } /* - * mdcreate() -- Create a new relation on magnetic disk. + * mdcreate() -- Create a new relation on magnetic disk. * * If isRedo is true, it's okay for the relation to exist already. */ @@ -242,7 +242,7 @@ mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo) } /* - * mdunlink() -- Unlink a relation. + * mdunlink() -- Unlink a relation. * * Note that we're passed a RelFileLocatorBackend --- by the time this is called, * there won't be an SMgrRelation hashtable entry anymore. @@ -447,13 +447,13 @@ mdunlinkfork(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo) } /* - * mdextend() -- Add a block to the specified relation. + * mdextend() -- Add a block to the specified relation. * - * The semantics are nearly the same as mdwrite(): write at the - * specified position. However, this is to be used for the case of - * extending a relation (i.e., blocknum is at or beyond the current - * EOF). Note that we assume writing a block beyond current EOF - * causes intervening file space to become filled with zeroes. + * The semantics are nearly the same as mdwrite(): write at the + * specified position. However, this is to be used for the case of + * extending a relation (i.e., blocknum is at or beyond the current + * EOF). Note that we assume writing a block beyond current EOF + * causes intervening file space to become filled with zeroes. */ void mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, @@ -515,10 +515,10 @@ mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, } /* - * mdzeroextend() -- Add new zeroed out blocks to the specified relation. + * mdzeroextend() -- Add new zeroed out blocks to the specified relation. * - * Similar to mdextend(), except the relation can be extended by multiple - * blocks at once and the added blocks will be filled with zeroes. + * Similar to mdextend(), except the relation can be extended by multiple + * blocks at once and the added blocks will be filled with zeroes. */ void mdzeroextend(SMgrRelation reln, ForkNumber forknum, @@ -623,7 +623,7 @@ mdzeroextend(SMgrRelation reln, ForkNumber forknum, } /* - * mdopenfork() -- Open one fork of the specified relation. + * mdopenfork() -- Open one fork of the specified relation. * * Note we only open the first segment, when there are multiple segments. * @@ -673,7 +673,7 @@ mdopenfork(SMgrRelation reln, ForkNumber forknum, int behavior) } /* - * mdopen() -- Initialize newly-opened relation. + * mdopen() -- Initialize newly-opened relation. */ void mdopen(SMgrRelation reln) @@ -684,7 +684,7 @@ mdopen(SMgrRelation reln) } /* - * mdclose() -- Close the specified relation, if it isn't closed already. + * mdclose() -- Close the specified relation, if it isn't closed already. */ void mdclose(SMgrRelation reln, ForkNumber forknum) @@ -707,7 +707,7 @@ mdclose(SMgrRelation reln, ForkNumber forknum) } /* - * mdprefetch() -- Initiate asynchronous read of the specified block of a relation + * mdprefetch() -- Initiate asynchronous read of the specified block of a relation */ bool mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum) @@ -791,7 +791,7 @@ mdwriteback(SMgrRelation reln, ForkNumber forknum, } /* - * mdread() -- Read the specified block from a relation. + * mdread() -- Read the specified block from a relation. */ void mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, @@ -856,11 +856,11 @@ mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, } /* - * mdwrite() -- Write the supplied block at the appropriate location. + * mdwrite() -- Write the supplied block at the appropriate location. * - * This is to be used only for updating already-existing blocks of a - * relation (ie, those before the current EOF). To extend a relation, - * use mdextend(). + * This is to be used only for updating already-existing blocks of a + * relation (ie, those before the current EOF). To extend a relation, + * use mdextend(). */ void mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, @@ -924,12 +924,12 @@ mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, } /* - * mdnblocks() -- Get the number of blocks stored in a relation. + * mdnblocks() -- Get the number of blocks stored in a relation. * - * Important side effect: all active segments of the relation are opened - * and added to the md_seg_fds array. If this routine has not been - * called, then only segments up to the last one actually touched - * are present in the array. + * Important side effect: all active segments of the relation are opened + * and added to the md_seg_fds array. If this routine has not been + * called, then only segments up to the last one actually touched + * are present in the array. */ BlockNumber mdnblocks(SMgrRelation reln, ForkNumber forknum) @@ -986,7 +986,7 @@ mdnblocks(SMgrRelation reln, ForkNumber forknum) } /* - * mdtruncate() -- Truncate relation to specified number of blocks. + * mdtruncate() -- Truncate relation to specified number of blocks. */ void mdtruncate(SMgrRelation reln, ForkNumber forknum, BlockNumber nblocks) @@ -1080,7 +1080,7 @@ mdtruncate(SMgrRelation reln, ForkNumber forknum, BlockNumber nblocks) } /* - * mdimmedsync() -- Immediately sync a relation to stable storage. + * mdimmedsync() -- Immediately sync a relation to stable storage. * * Note that only writes already issued are synced; this routine knows * nothing of dirty buffers that may exist inside the buffer manager. We @@ -1275,7 +1275,7 @@ DropRelationFiles(RelFileLocator *delrels, int ndelrels, bool isRedo) /* - * _fdvec_resize() -- Resize the fork's open segments array + * _fdvec_resize() -- Resize the fork's open segments array */ static void _fdvec_resize(SMgrRelation reln, @@ -1376,8 +1376,8 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno, } /* - * _mdfd_getseg() -- Find the segment of the relation holding the - * specified block. + * _mdfd_getseg() -- Find the segment of the relation holding the + * specified block. * * If the segment doesn't exist, we ereport, return NULL, or create the * segment, according to "behavior". Note: skipFsync is only used in the |