Memory QueryContext

执行阶段

TopPortalContext
└── PortalContext
    └── QueryContext("ExecutorState")
        ├── ExprContext
        ├── tmpcontext("printtup")
        └── SortContext | HashContext

"simple Query"

MemoryContextSwitchTo(MessageContext);
MemoryContextResetAndDeleteChildren(MessageContext);
exec_simple_query

    /* create and switch to TopTransactionContext */
    start_xact_command | StartTransactionCommand | StartTransaction | AtStart_Memory
        TopTransactionContext =  AllocSetContextCreate(TopMemoryContext, ...)
        CurTransactionContext = TopTransactionContext;
        MemoryContextSwitchTo(CurTransactionContext);

    /* ... */

    MemoryContextSwitchTo(MessageContext);
    pg_parse_query
    pg_analyze_and_rewrite_fixedparams
    pg_plan_queries


    CreatePortal
        portal->portalContext = AllocSetContextCreate(TopPortalContext, ...)

    PortalStart
        MemoryContextSwitchTo(PortalContext)
        CreateQueryDesc
        ExecutorStart | standard_ExecutorStart | standard_ExecutorStart
            estate = CreateExecutorState()
                qcontext = AllocSetContextCreate(CurrentMemoryContext, ...)
                MemoryContextSwitchTo(qcontext)
                estate = makeNode(EState);
                estate->es_query_cxt = qcontext

            MemoryContextSwitchTo(estate->es_query_cxt)
            InitPlan | ExecInitNode | ExecInitSeqScan

                /* create expression context for node */
                ExecAssignExprContext
                    planstate->ps_ExprContext = CreateExprContext(estate);
                        CreateExprContextInternal
                            econtext->ecxt_per_tuple_memory = AllocSetContextCreate(estate->es_query_cxt, "ExprContext")
                            return econtext;
    /* ... */

    PortalRun
        MemoryContextSwitchTo(PortalContext)
        PortalRunSelect
            /* ... */

    PortalDrop
        portal->cleanup(portal);
            PortalCleanup
                ExecutorFinish
                ExecutorEnd | standard_ExecutorEnd | FreeExecutorState
                    FreeExprContext
                        MemoryContextDelete(econtext->ecxt_per_tuple_memory);
                    MemoryContextDelete(estate->es_query_cxt);
        MemoryContextDelete(portal->portalContext);

    finish_xact_command | CommitTransactionCommand | CommitTransaction
        AtCommit_Memory
            MemoryContextSwitchTo(TopMemoryContext);
            MemoryContextDelete(TopTransactionContext);

PortalRun

PortalRun
    MemoryContextSwitchTo(PortalContext)
    PortalRunSelect
        ExecutorRun | standard_ExecutorRun
            MemoryContextSwitchTo(estate->es_query_cxt)
            printtup_startup
                /* a temporary memory context that we can reset once per row to recover palloc'd memory */
                myState->tmpcontext = AllocSetContextCreate(CurrentMemoryContext, "printtup", ...)
            ExecutePlan /* Loop until we've processed the proper number of tuples from the plan. */

                ResetPerTupleExprContext(estate); /* (estate)->es_per_tuple_exprcontext */

                ExecProcNode | ExecSeqScan | ExecScan
                    ResetExprContext(node->ps.ps_ExprContext);

                    /* get a tuple for(;;)*/
                    ExecProject
                        ExecEvalExprSwitchContext
                            oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
                            retDatum = state->evalfunc(state, econtext, isNull);
                            MemoryContextSwitchTo(oldContext);
                            return retDatum;
                printtup
                    /* Switch into per-row context so we can recover memory below */
                    oldcontext = MemoryContextSwitchTo(myState->tmpcontext);

                    /* send message, text/binary */

                    MemoryContextSwitchTo(QueryContext)
                    MemoryContextReset(myState->tmpcontext)
        dest->rShutdown(dest);
            printtup_shutdown
                MemoryContextDelete(myState->tmpcontext);