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Commite1b120a

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Only issue LOCK TABLE commands when necessary
Reviewing the cases where we need to LOCK a given table during a dump,it was pointed out by Tom that we really don't need to LOCK a table ifwe are only looking to dump the ACL for it, or certain othercomponents. After reviewing the queries run for all of the componentpieces, a list of components were determined to not require LOCK'ingof the table.This implements a check to avoid LOCK'ing those tables.Initial complaint from Rushabh Lathia, discussed with Robert and Tom,the patch is mine.
1 parent5d58999 commite1b120a

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2 files changed

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‎src/bin/pg_dump/pg_dump.c

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5953,8 +5953,11 @@ getTables(Archive *fout, int *numTables)
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*
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* NOTE: it'd be kinda nice to lock other relations too, not only
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* plain tables, but the backend doesn't presently allow that.
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*
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* We only need to lock the table for certain components; see pg_dump.h
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*/
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if (tblinfo[i].dobj.dump && tblinfo[i].relkind == RELKIND_RELATION)
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if (tblinfo[i].dobj.dump && tblinfo[i].relkind == RELKIND_RELATION &&
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(tblinfo[i].dobj.dump & DUMP_COMPONENTS_REQUIRING_LOCK))
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{
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resetPQExpBuffer(query);
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appendPQExpBuffer(query,

‎src/bin/pg_dump/pg_dump.h

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -93,6 +93,33 @@ typedef uint32 DumpComponents;/* a bitmask of dump object components */
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#defineDUMP_COMPONENT_USERMAP(1 << 6)
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#defineDUMP_COMPONENT_ALL(0xFFFF)
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/*
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* component types which require us to obtain a lock on the table
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*
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* Note that some components only require looking at the information
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* in the pg_catalog tables and, for those components, we do not need
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* to lock the table. Be careful here though- some components use
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* server-side functions which pull the latest information from
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* SysCache and in those cases we *do* need to lock the table.
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*
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* We do not need locks for the COMMENT and SECLABEL components as
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* those simply query their associated tables without using any
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* server-side functions. We do not need locks for the ACL component
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* as we pull that information from pg_class without using any
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* server-side functions that use SysCache. The USERMAP component
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* is only relevant for FOREIGN SERVERs and not tables, so no sense
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* locking a table for that either (that can happen if we are going
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* to dump "ALL" components for a table).
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*
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* We DO need locks for DEFINITION, due to various server-side
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* functions that are used and POLICY due to pg_get_expr(). We set
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* this up to grab the lock except in the cases we know to be safe.
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*/
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#defineDUMP_COMPONENTS_REQUIRING_LOCK (\
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DUMP_COMPONENT_DEFINITION |\
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DUMP_COMPONENT_DATA |\
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DUMP_COMPONENT_POLICY)
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typedefstruct_dumpableObject
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{
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DumpableObjectTypeobjType;

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