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Restructure SELECT INTO's parsetree representation into CreateTableAsStmt.

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Making this operation look like a utility statement seems generally a good
idea, and particularly so in light of the desire to provide command
triggers for utility statements.  The original choice of representing it as
SELECT with an IntoClause appendage had metastasized into rather a lot of
places, unfortunately, so that this patch is a great deal more complicated
than one might at first expect.

In particular, keeping EXPLAIN working for SELECT INTO and CREATE TABLE AS
subcommands required restructuring some EXPLAIN-related APIs.  Add-on code
that calls ExplainOnePlan or ExplainOneUtility, or uses
ExplainOneQuery_hook, will need adjustment.

Also, the cases PREPARE ... SELECT INTO and CREATE RULE ... SELECT INTO,
which formerly were accepted though undocumented, are no longer accepted.
The PREPARE case can be replaced with use of CREATE TABLE AS EXECUTE.
The CREATE RULE case doesn't seem to have much real-world use (since the
rule would work only once before failing with "table already exists"),
so we'll not bother with that one.

Both SELECT INTO and CREATE TABLE AS still return a command tag of
"SELECT nnnn".  There was some discussion of returning "CREATE TABLE nnnn",
but for the moment backwards compatibility wins the day.

Andres Freund and Tom Lane
This commit is contained in:
Tom Lane
2012-03-19 21:37:19 -04:00
parent 77503a7638
commit 9dbf2b7d75
47 changed files with 963 additions and 729 deletions
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39
src/backend/tcop/pquery.c
View File

@ -260,8 +260,7 @@ ChoosePortalStrategy(List *stmts)
if (query->canSetTag)
{
if (query->commandType == CMD_SELECT &&
query->utilityStmt == NULL &&
query->intoClause == NULL)
query->utilityStmt == NULL)
{
if (query->hasModifyingCTE)
return PORTAL_ONE_MOD_WITH;
@ -285,8 +284,7 @@ ChoosePortalStrategy(List *stmts)
if (pstmt->canSetTag)
{
if (pstmt->commandType == CMD_SELECT &&
pstmt->utilityStmt == NULL &&
pstmt->intoClause == NULL)
pstmt->utilityStmt == NULL)
{
if (pstmt->hasModifyingCTE)
return PORTAL_ONE_MOD_WITH;
@ -395,8 +393,7 @@ FetchStatementTargetList(Node *stmt)
else
{
if (query->commandType == CMD_SELECT &&
query->utilityStmt == NULL &&
query->intoClause == NULL)
query->utilityStmt == NULL)
return query->targetList;
if (query->returningList)
return query->returningList;
@ -408,8 +405,7 @@ FetchStatementTargetList(Node *stmt)
PlannedStmt *pstmt = (PlannedStmt *) stmt;
if (pstmt->commandType == CMD_SELECT &&
pstmt->utilityStmt == NULL &&
pstmt->intoClause == NULL)
pstmt->utilityStmt == NULL)
return pstmt->planTree->targetlist;
if (pstmt->hasReturning)
return pstmt->planTree->targetlist;
@ -430,7 +426,6 @@ FetchStatementTargetList(Node *stmt)
ExecuteStmt *estmt = (ExecuteStmt *) stmt;
PreparedStatement *entry;
Assert(!estmt->into);
entry = FetchPreparedStatement(estmt->name, true);
return FetchPreparedStatementTargetList(entry);
}
@ -442,9 +437,15 @@ FetchStatementTargetList(Node *stmt)
* Prepare a portal for execution.
*
* Caller must already have created the portal, done PortalDefineQuery(),
* and adjusted portal options if needed. If parameters are needed by
* the query, they must be passed in here (caller is responsible for
* giving them appropriate lifetime).
* and adjusted portal options if needed.
*
* If parameters are needed by the query, they must be passed in "params"
* (caller is responsible for giving them appropriate lifetime).
*
* The caller can also provide an initial set of "eflags" to be passed to
* ExecutorStart (but note these can be modified internally, and they are
* currently only honored for PORTAL_ONE_SELECT portals). Most callers
* should simply pass zero.
*
* The use_active_snapshot parameter is currently used only for
* PORTAL_ONE_SELECT portals. If it is true, the active snapshot will
@ -456,14 +457,15 @@ FetchStatementTargetList(Node *stmt)
* tupdesc (if any) is known.
*/
void
PortalStart(Portal portal, ParamListInfo params, bool use_active_snapshot)
PortalStart(Portal portal, ParamListInfo params,
int eflags, bool use_active_snapshot)
{
Portal saveActivePortal;
ResourceOwner saveResourceOwner;
MemoryContext savePortalContext;
MemoryContext oldContext;
QueryDesc *queryDesc;
int eflags;
int myeflags;
AssertArg(PortalIsValid(portal));
AssertState(portal->status == PORTAL_DEFINED);
@ -517,17 +519,18 @@ PortalStart(Portal portal, ParamListInfo params, bool use_active_snapshot)
/*
* If it's a scrollable cursor, executor needs to support
* REWIND and backwards scan.
* REWIND and backwards scan, as well as whatever the caller
* might've asked for.
*/
if (portal->cursorOptions & CURSOR_OPT_SCROLL)
eflags = EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD;
myeflags = eflags | EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD;
else
eflags = 0; /* default run-to-completion flags */
myeflags = eflags;
/*
* Call ExecutorStart to prepare the plan for execution
*/
ExecutorStart(queryDesc, eflags);
ExecutorStart(queryDesc, myeflags);
/*
* This tells PortalCleanup to shut down the executor