greenplumn prepare 源码
greenplumn prepare 代码
文件路径：/src/backend/commands/prepare.c
/*-------------------------------------------------------------------------
*
* prepare.c
* Prepareable SQL statements via PREPARE, EXECUTE and DEALLOCATE
*
* This module also implements storage of prepared statements that are
* accessed via the extended FE/BE query protocol.
*
*
* Copyright (c) 2002-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/commands/prepare.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "commands/createas.h"
#include "commands/prepare.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "parser/analyze.h"
#include "parser/parse_coerce.h"
#include "parser/parse_collate.h"
#include "parser/parse_expr.h"
#include "parser/parse_type.h"
#include "rewrite/rewriteHandler.h"
#include "tcop/pquery.h"
#include "tcop/utility.h"
#include "utils/builtins.h"
#include "utils/snapmgr.h"
#include "utils/timestamp.h"
/*
* The hash table in which prepared queries are stored. This is
* per-backend: query plans are not shared between backends.
* The keys for this hash table are the arguments to PREPARE and EXECUTE
* (statement names); the entries are PreparedStatement structs.
*/
static HTAB *prepared_queries = NULL;
static void InitQueryHashTable(void);
static ParamListInfo EvaluateParams(PreparedStatement *pstmt, List *params,
const char *queryString, EState *estate);
static Datum build_regtype_array(Oid *param_types, int num_params);
/*
* Implements the 'PREPARE' utility statement.
*/
void
PrepareQuery(PrepareStmt *stmt, const char *queryString,
int stmt_location, int stmt_len)
{
RawStmt *rawstmt;
CachedPlanSource *plansource;
Oid *argtypes = NULL;
int nargs;
Query *query;
List *query_list;
int i;
NodeTag srctag; /* GPDB */
/*
* Disallow empty-string statement name (conflicts with protocol-level
* unnamed statement).
*/
if (!stmt->name || stmt->name[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_PSTATEMENT_DEFINITION),
errmsg("invalid statement name: must not be empty")));
/*
* Need to wrap the contained statement in a RawStmt node to pass it to
* parse analysis.
*
* Because parse analysis scribbles on the raw querytree, we must make a
* copy to ensure we don't modify the passed-in tree. FIXME someday.
*/
rawstmt = makeNode(RawStmt);
rawstmt->stmt = (Node *) copyObject(stmt->query);
rawstmt->stmt_location = stmt_location;
rawstmt->stmt_len = stmt_len;
/*
* Create the CachedPlanSource before we do parse analysis, since it needs
* to see the unmodified raw parse tree.
*/
plansource = CreateCachedPlan(rawstmt, queryString,
CreateCommandTag(stmt->query));
/* Transform list of TypeNames to array of type OIDs */
nargs = list_length(stmt->argtypes);
if (nargs)
{
ParseState *pstate;
ListCell *l;
/*
* typenameTypeId wants a ParseState to carry the source query string.
* Is it worth refactoring its API to avoid this?
*/
pstate = make_parsestate(NULL);
pstate->p_sourcetext = queryString;
argtypes = (Oid *) palloc(nargs * sizeof(Oid));
i = 0;
foreach(l, stmt->argtypes)
{
TypeName *tn = lfirst(l);
Oid toid = typenameTypeId(pstate, tn);
argtypes[i++] = toid;
}
}
/*
* Analyze the statement using these parameter types (any parameters
* passed in from above us will not be visible to it), allowing
* information about unknown parameters to be deduced from context.
*/
query = parse_analyze_varparams(rawstmt, queryString,
&argtypes, &nargs);
/*
* Check that all parameter types were determined.
*/
for (i = 0; i < nargs; i++)
{
Oid argtype = argtypes[i];
if (argtype == InvalidOid || argtype == UNKNOWNOID)
ereport(ERROR,
(errcode(ERRCODE_INDETERMINATE_DATATYPE),
errmsg("could not determine data type of parameter $%d",
i + 1)));
}
/*
* grammar only allows OptimizableStmt, so this check should be redundant
*/
switch (query->commandType)
{
case CMD_SELECT:
srctag = T_SelectStmt;
break;
case CMD_INSERT:
srctag = T_InsertStmt;
break;
case CMD_UPDATE:
srctag = T_UpdateStmt;
break;
case CMD_DELETE:
srctag = T_DeleteStmt;
break;
default:
ereport(ERROR,
(errcode(ERRCODE_INVALID_PSTATEMENT_DEFINITION),
errmsg("utility statements cannot be prepared")));
srctag = T_Query; /* keep compiler quiet */
break;
}
/* Rewrite the query. The result could be 0, 1, or many queries. */
query_list = QueryRewrite(query);
/* Finish filling in the CachedPlanSource */
CompleteCachedPlan(plansource,
query_list,
NULL,
srctag,
argtypes,
nargs,
NULL,
NULL,
CURSOR_OPT_PARALLEL_OK, /* allow parallel mode */
true); /* fixed result */
/*
* Save the results.
*/
StorePreparedStatement(stmt->name,
plansource,
true);
}
/*
* ExecuteQuery --- implement the 'EXECUTE' utility statement.
*
* This code also supports CREATE TABLE ... AS EXECUTE. That case is
* indicated by passing a non-null intoClause. The DestReceiver is already
* set up correctly for CREATE TABLE AS, but we still have to make a few
* other adjustments here.
*
* Note: this is one of very few places in the code that needs to deal with
* two query strings at once. The passed-in queryString is that of the
* EXECUTE, which we might need for error reporting while processing the
* parameter expressions. The query_string that we copy from the plan
* source is that of the original PREPARE.
*/
void
ExecuteQuery(ExecuteStmt *stmt, IntoClause *intoClause,
const char *queryString, ParamListInfo params,
DestReceiver *dest, char *completionTag)
{
PreparedStatement *entry;
CachedPlan *cplan;
List *plan_list;
ParamListInfo paramLI = NULL;
EState *estate = NULL;
Portal portal;
char *query_string;
int eflags;
long count;
/* Look it up in the hash table */
entry = FetchPreparedStatement(stmt->name, true);
/* Shouldn't find a non-fixed-result cached plan */
if (!entry->plansource->fixed_result)
elog(ERROR, "EXECUTE does not support variable-result cached plans");
/* Evaluate parameters, if any */
if (entry->plansource->num_params > 0)
{
/*
* Need an EState to evaluate parameters; must not delete it till end
* of query, in case parameters are pass-by-reference. Note that the
* passed-in "params" could possibly be referenced in the parameter
* expressions.
*/
estate = CreateExecutorState();
estate->es_param_list_info = params;
paramLI = EvaluateParams(entry, stmt->params,
queryString, estate);
}
/* Create a new portal to run the query in */
portal = CreateNewPortal();
/* Don't display the portal in pg_cursors, it is for internal use only */
portal->visible = false;
/* Copy the plan's saved query string into the portal's memory */
query_string = MemoryContextStrdup(portal->portalContext,
entry->plansource->query_string);
/* Replan if needed, and increment plan refcount for portal */
cplan = GetCachedPlan(entry->plansource, paramLI, false, NULL, intoClause);
plan_list = cplan->stmt_list;
/*
* For CREATE TABLE / AS EXECUTE, we must make a copy of the stored query
* so that we can modify its destination (yech, but this has always been
* ugly). For regular EXECUTE we can just use the cached query, since the
* executor is read-only.
*
* In GPDB, we use the current parameter values in the planning, because
* that potentially gives a better plan. It also means that we have to
* re-plan the query on every EXECUTE, but for long-running OLAP queries
* that GPDB is typically used for, that seems like a good tradeoff.
*
* In GPDB the plan for CREATE TABLE / AS EXECUTE also depends on the
* DISTRIBUTED BY clause of the target table. For example, if the table is
* distributed by 'column1', then the rows to insert must be moved to the
* correct nodes, determined by 'column1'. That's a very different plan
* than what you get if you run the plain SELECT from the master; in that
* case all the output rows will be fetched into the master. Because of
* that, we also have to pass the into-clause to
* RevalidateCachedPlanWithParams. (MPP-8135)
*/
if (intoClause)
{
PlannedStmt *pstmt;
if (list_length(plan_list) != 1)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT")));
pstmt = linitial_node(PlannedStmt, plan_list);
if (pstmt->commandType != CMD_SELECT)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("prepared statement is not a SELECT")));
/*GPDB: Save the target information in PlannedStmt */
pstmt->intoClause = copyObject(intoClause);
/* Set appropriate eflags */
eflags = GetIntoRelEFlags(intoClause);
/* And tell PortalRun whether to run to completion or not */
if (intoClause->skipData)
count = 0;
else
count = FETCH_ALL;
}
else
{
/* Plain old EXECUTE */
eflags = 0;
count = FETCH_ALL;
}
PortalDefineQuery(portal,
NULL,
query_string,
entry->plansource->sourceTag,
entry->plansource->commandTag,
plan_list,
cplan);
/*
* Run the portal as appropriate.
*/
PortalStart(portal, paramLI, eflags, GetActiveSnapshot(), NULL);
(void) PortalRun(portal, count, false, true, dest, dest, completionTag);
PortalDrop(portal, false);
if (estate)
FreeExecutorState(estate);
/* No need to pfree other memory, MemoryContext will be reset */
}
/*
* EvaluateParams: evaluate a list of parameters.
*
* pstmt: statement we are getting parameters for.
* params: list of given parameter expressions (raw parser output!)
* queryString: source text for error messages.
* estate: executor state to use.
*
* Returns a filled-in ParamListInfo -- this can later be passed to
* CreateQueryDesc(), which allows the executor to make use of the parameters
* during query execution.
*/
static ParamListInfo
EvaluateParams(PreparedStatement *pstmt, List *params,
const char *queryString, EState *estate)
{
Oid *param_types = pstmt->plansource->param_types;
int num_params = pstmt->plansource->num_params;
int nparams = list_length(params);
ParseState *pstate;
ParamListInfo paramLI;
List *exprstates;
ListCell *l;
int i;
if (nparams != num_params)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("wrong number of parameters for prepared statement \"%s\"",
pstmt->stmt_name),
errdetail("Expected %d parameters but got %d.",
num_params, nparams)));
/* Quick exit if no parameters */
if (num_params == 0)
return NULL;
/*
* We have to run parse analysis for the expressions. Since the parser is
* not cool about scribbling on its input, copy first.
*/
params = copyObject(params);
pstate = make_parsestate(NULL);
pstate->p_sourcetext = queryString;
i = 0;
foreach(l, params)
{
Node *expr = lfirst(l);
Oid expected_type_id = param_types[i];
Oid given_type_id;
expr = transformExpr(pstate, expr, EXPR_KIND_EXECUTE_PARAMETER);
given_type_id = exprType(expr);
expr = coerce_to_target_type(pstate, expr, given_type_id,
expected_type_id, -1,
COERCION_ASSIGNMENT,
COERCE_IMPLICIT_CAST,
-1);
if (expr == NULL)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("parameter $%d of type %s cannot be coerced to the expected type %s",
i + 1,
format_type_be(given_type_id),
format_type_be(expected_type_id)),
errhint("You will need to rewrite or cast the expression.")));
/* Take care of collations in the finished expression. */
assign_expr_collations(pstate, expr);
lfirst(l) = expr;
i++;
}
/* Prepare the expressions for execution */
exprstates = ExecPrepareExprList(params, estate);
paramLI = makeParamList(num_params);
i = 0;
foreach(l, exprstates)
{
ExprState *n = (ExprState *) lfirst(l);
ParamExternData *prm = ¶mLI->params[i];
prm->ptype = param_types[i];
prm->pflags = PARAM_FLAG_CONST;
prm->value = ExecEvalExprSwitchContext(n,
GetPerTupleExprContext(estate),
&prm->isnull);
i++;
}
return paramLI;
}
/*
* Initialize query hash table upon first use.
*/
static void
InitQueryHashTable(void)
{
HASHCTL hash_ctl;
MemSet(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = NAMEDATALEN;
hash_ctl.entrysize = sizeof(PreparedStatement);
prepared_queries = hash_create("Prepared Queries",
32,
&hash_ctl,
HASH_ELEM);
}
/*
* Store all the data pertaining to a query in the hash table using
* the specified key. The passed CachedPlanSource should be "unsaved"
* in case we get an error here; we'll save it once we've created the hash
* table entry.
* The original query nodetag is saved as well, only used if resource
* scheduling is enabled.
*/
void
StorePreparedStatement(const char *stmt_name,
CachedPlanSource *plansource,
bool from_sql)
{
PreparedStatement *entry;
TimestampTz cur_ts = GetCurrentStatementStartTimestamp();
bool found;
/* Initialize the hash table, if necessary */
if (!prepared_queries)
InitQueryHashTable();
/* Add entry to hash table */
entry = (PreparedStatement *) hash_search(prepared_queries,
stmt_name,
HASH_ENTER,
&found);
/* Shouldn't get a duplicate entry */
if (found)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_PSTATEMENT),
errmsg("prepared statement \"%s\" already exists",
stmt_name)));
/* Fill in the hash table entry */
entry->plansource = plansource;
entry->from_sql = from_sql;
entry->prepare_time = cur_ts;
/* Now it's safe to move the CachedPlanSource to permanent memory */
SaveCachedPlan(plansource);
}
/*
* Lookup an existing query in the hash table. If the query does not
* actually exist, throw ereport(ERROR) or return NULL per second parameter.
*
* Note: this does not force the referenced plancache entry to be valid,
* since not all callers care.
*/
PreparedStatement *
FetchPreparedStatement(const char *stmt_name, bool throwError)
{
PreparedStatement *entry;
/*
* If the hash table hasn't been initialized, it can't be storing
* anything, therefore it couldn't possibly store our plan.
*/
if (prepared_queries)
entry = (PreparedStatement *) hash_search(prepared_queries,
stmt_name,
HASH_FIND,
NULL);
else
entry = NULL;
if (!entry && throwError)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_PSTATEMENT),
errmsg("prepared statement \"%s\" does not exist",
stmt_name)));
return entry;
}
/*
* Given a prepared statement, determine the result tupledesc it will
* produce. Returns NULL if the execution will not return tuples.
*
* Note: the result is created or copied into current memory context.
*/
TupleDesc
FetchPreparedStatementResultDesc(PreparedStatement *stmt)
{
/*
* Since we don't allow prepared statements' result tupdescs to change,
* there's no need to worry about revalidating the cached plan here.
*/
Assert(stmt->plansource->fixed_result);
if (stmt->plansource->resultDesc)
return CreateTupleDescCopy(stmt->plansource->resultDesc);
else
return NULL;
}
/*
* Given a prepared statement that returns tuples, extract the query
* targetlist. Returns NIL if the statement doesn't have a determinable
* targetlist.
*
* Note: this is pretty ugly, but since it's only used in corner cases like
* Describe Statement on an EXECUTE command, we don't worry too much about
* efficiency.
*/
List *
FetchPreparedStatementTargetList(PreparedStatement *stmt)
{
List *tlist;
/* Get the plan's primary targetlist */
tlist = CachedPlanGetTargetList(stmt->plansource, NULL);
/* Copy into caller's context in case plan gets invalidated */
return copyObject(tlist);
}
/*
* Implements the 'DEALLOCATE' utility statement: deletes the
* specified plan from storage.
*/
void
DeallocateQuery(DeallocateStmt *stmt)
{
if (stmt->name)
DropPreparedStatement(stmt->name, true);
else
DropAllPreparedStatements();
}
/*
* Internal version of DEALLOCATE
*
* If showError is false, dropping a nonexistent statement is a no-op.
*/
void
DropPreparedStatement(const char *stmt_name, bool showError)
{
PreparedStatement *entry;
/* Find the query's hash table entry; raise error if wanted */
entry = FetchPreparedStatement(stmt_name, showError);
if (entry)
{
/* Release the plancache entry */
DropCachedPlan(entry->plansource);
/* Now we can remove the hash table entry */
hash_search(prepared_queries, entry->stmt_name, HASH_REMOVE, NULL);
}
}
/*
* Drop all cached statements.
*/
void
DropAllPreparedStatements(void)
{
HASH_SEQ_STATUS seq;
PreparedStatement *entry;
/* nothing cached */
if (!prepared_queries)
return;
/* walk over cache */
hash_seq_init(&seq, prepared_queries);
while ((entry = hash_seq_search(&seq)) != NULL)
{
/* Release the plancache entry */
DropCachedPlan(entry->plansource);
/* Now we can remove the hash table entry */
hash_search(prepared_queries, entry->stmt_name, HASH_REMOVE, NULL);
}
}
/*
* Implements the 'EXPLAIN EXECUTE' utility statement.
*
* "into" is NULL unless we are doing EXPLAIN CREATE TABLE AS EXECUTE,
* in which case executing the query should result in creating that table.
*
* Note: the passed-in queryString is that of the EXPLAIN EXECUTE,
* not the original PREPARE; we get the latter string from the plancache.
*/
void
ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
const char *queryString, ParamListInfo params,
QueryEnvironment *queryEnv)
{
PreparedStatement *entry;
const char *query_string;
CachedPlan *cplan;
List *plan_list;
ListCell *p;
ParamListInfo paramLI = NULL;
EState *estate = NULL;
instr_time planstart;
instr_time planduration;
INSTR_TIME_SET_CURRENT(planstart);
/* Look it up in the hash table */
entry = FetchPreparedStatement(execstmt->name, true);
/* Shouldn't find a non-fixed-result cached plan */
if (!entry->plansource->fixed_result)
elog(ERROR, "EXPLAIN EXECUTE does not support variable-result cached plans");
/*
* In Greenplum we first need to evaluate the parameters since we pass
* paramLI to RevalidateCachedPlanWithParams(), while PostgreSQL uses
* RevalidateCachedPlan().
*/
/* Evaluate parameters, if any */
if (entry->plansource->num_params)
{
/*
* Need an EState to evaluate parameters; must not delete it till end
* of query, in case parameters are pass-by-reference.
*/
estate = CreateExecutorState();
estate->es_param_list_info = params;
paramLI = EvaluateParams(entry, execstmt->params,
queryString, estate);
}
query_string = entry->plansource->query_string;
/* Evaluate parameters, if any */
if (entry->plansource->num_params)
{
/*
* Need an EState to evaluate parameters; must not delete it till end
* of query, in case parameters are pass-by-reference. Note that the
* passed-in "params" could possibly be referenced in the parameter
* expressions.
*/
estate = CreateExecutorState();
estate->es_param_list_info = params;
paramLI = EvaluateParams(entry, execstmt->params,
queryString, estate);
}
/* Replan if needed, and acquire a transient refcount */
cplan = GetCachedPlan(entry->plansource, paramLI, true, queryEnv, into);
INSTR_TIME_SET_CURRENT(planduration);
INSTR_TIME_SUBTRACT(planduration, planstart);
plan_list = cplan->stmt_list;
/* Explain each query */
foreach(p, plan_list)
{
PlannedStmt *pstmt = lfirst_node(PlannedStmt, p);
if (pstmt->commandType != CMD_UTILITY)
ExplainOnePlan(pstmt, into, es, query_string, paramLI, queryEnv,
&planduration, 0);
else
ExplainOneUtility(pstmt->utilityStmt, into, es, query_string,
paramLI, queryEnv);
/* No need for CommandCounterIncrement, as ExplainOnePlan did it */
/* Separate plans with an appropriate separator */
if (lnext(p) != NULL)
ExplainSeparatePlans(es);
}
if (estate)
FreeExecutorState(estate);
ReleaseCachedPlan(cplan, true);
}
/*
* This set returning function reads all the prepared statements and
* returns a set of (name, statement, prepare_time, param_types, from_sql).
*/
Datum
pg_prepared_statement(PG_FUNCTION_ARGS)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
MemoryContext per_query_ctx;
MemoryContext oldcontext;
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("materialize mode required, but it is not " \
"allowed in this context")));
/* need to build tuplestore in query context */
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
oldcontext = MemoryContextSwitchTo(per_query_ctx);
/*
* build tupdesc for result tuples. This must match the definition of the
* pg_prepared_statements view in system_views.sql
*/
tupdesc = CreateTemplateTupleDesc(5);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 3, "prepare_time",
TIMESTAMPTZOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 4, "parameter_types",
REGTYPEARRAYOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 5, "from_sql",
BOOLOID, -1, 0);
/*
* We put all the tuples into a tuplestore in one scan of the hashtable.
* This avoids any issue of the hashtable possibly changing between calls.
*/
tupstore =
tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
false, work_mem);
/* generate junk in short-term context */
MemoryContextSwitchTo(oldcontext);
/* hash table might be uninitialized */
if (prepared_queries)
{
HASH_SEQ_STATUS hash_seq;
PreparedStatement *prep_stmt;
hash_seq_init(&hash_seq, prepared_queries);
while ((prep_stmt = hash_seq_search(&hash_seq)) != NULL)
{
Datum values[5];
bool nulls[5];
MemSet(nulls, 0, sizeof(nulls));
values[0] = CStringGetTextDatum(prep_stmt->stmt_name);
values[1] = CStringGetTextDatum(prep_stmt->plansource->query_string);
values[2] = TimestampTzGetDatum(prep_stmt->prepare_time);
values[3] = build_regtype_array(prep_stmt->plansource->param_types,
prep_stmt->plansource->num_params);
values[4] = BoolGetDatum(prep_stmt->from_sql);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}
}
/* clean up and return the tuplestore */
tuplestore_donestoring(tupstore);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
return (Datum) 0;
}
/*
* This utility function takes a C array of Oids, and returns a Datum
* pointing to a one-dimensional Postgres array of regtypes. An empty
* array is returned as a zero-element array, not NULL.
*/
static Datum
build_regtype_array(Oid *param_types, int num_params)
{
Datum *tmp_ary;
ArrayType *result;
int i;
tmp_ary = (Datum *) palloc(num_params * sizeof(Datum));
for (i = 0; i < num_params; i++)
tmp_ary[i] = ObjectIdGetDatum(param_types[i]);
/* XXX: this hardcodes assumptions about the regtype type */
result = construct_array(tmp_ary, num_params, REGTYPEOID, 4, true, 'i');
return PointerGetDatum(result);
}
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