Overview

• A Comprehensive Overview of PostgreSQL Query Processing Stages
• The Internals of PostgreSQL: 3 Query Processing
• postgres.c

exec_simple_query

/* parse */
pg_parse_query
    raw_parser

/* analyze and rewrite */
pg_analyze_and_rewrite_fixedparams
    parse_analyze_fixedparams
    pg_rewrite_query

/* plan */
pg_plan_queries

/* execute */
PortalStart
    ExecutorStart
PortalRun - PortalRunSelect
    ExecutorRun
PortalDrop
    ExecutorFinish
    ExecutorEnd

完整调用栈

/* 1. Parse */
pg_parse_query // Parse by Bison(gram.y), support multi queries
    raw_parser

/* 2. Analyze & Rewrite */
pg_analyze_and_rewrite_fixedparams // analyze and rewrite RawStmt, RawStmt -> Query
    query = parse_analyze_fixedparams // Perform parse analysis. RawStmt -> Query
        transformTopLevelStmt - transformOptionalSelectInto - transformStmt
            transformSelectStmt
                Query      *qry = makeNode(Query);
                transform***Clause
    querytree_list = pg_rewrite_query // Rewrite the queries, as necessary. Query -> List(Query)
        QueryRewrite // don't rewrite utilities

/* 3. Plan */
pg_plan_queries // querytree_list -> plantree_list(PlannedStmt), plan just for dml(select, insert, update, delete, merge)
    pg_plan_query - planner - standard_planner - subquery_planner
        /* primary planning entry point (may recurse for subqueries) */
        root = subquery_planner(glob, parse, NULL, false, tuple_fraction);
        /* Select best Path and turn it into a Plan */
        final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
        best_path = get_cheapest_fractional_path(final_rel, tuple_fraction);
        PlannedStmt.planTree = create_plan(root, best_path);

/* 4. Portal */
CreatePortal
PortalDefineQuery // portal->stmts = plantree_list;
PortalStart // Prepare a portal for execution. params, strategy, queryDesc
    queryDesc = CreateQueryDesc
    ExecutorStart(queryDesc, myeflags); // prepare the plan for execution
        standard_ExecutorStart
    portal->queryDesc = queryDesc;
    portal->status = PORTAL_READY;
PortalSetResultFormat
PortalRun - PortalRunSelect

    /* 5. Executor */
    ExecutorRun - tandard_ExecutorRun - ExecutePlan // Processes the query plan until retrieved 'numberTuples' tuples
        ExecProcNode - ExecSeqScan
            ExecScan - ExecScanFetch - SeqNext // executor module
                /* Access + Storage*/
                table_scan_getnextslot - heap_getnextslot - heapgettup_pagemode
                    heapgetpage - ReadBufferExtended -  ReadBuffer_common

                        LockBuffer(buffer, BUFFER_LOCK_SHARE);

                        BufferGetPage - BufferGetBlock
                            return (Block) (BufferBlocks + ((Size) (buffer - 1)) * BLCKSZ);
                        for (lineoff = FirstOffsetNumber; lineoff <= lines; lineoff++)
                            PageGetItemId // Returns an item identifier of a page.
                                return &((PageHeader) page)->pd_linp[offsetNumber - 1];
                            PageGetItem // Retrieves an item on the given page.
                                return (Item) (((char *) page) + ItemIdGetOffset(itemId));

                        // True if heap tuple satisfies a time qual
                        HeapTupleSatisfiesVisibility - HeapTupleSatisfiesMVCC

                        LockBuffer(buffer, BUFFER_LOCK_UNLOCK);

                    ExecStorePinnedBufferHeapTuple // buffer tuple -> tuple table
                        tts_buffer_heap_store_tuple
                            IncrBufferRefCount
                            return slot;
                ExecProject
PortalDrop