Consider the scenario below

```
create table tenk1 (c1 int, ten int);
create temp sequence ts1;
explain select * from (select distinct ten from tenk1) ss where ten < 10 + nextval('ts1') order by 1;
```

The filter outside the subquery is a candidate to be pushed below the
'distinct' in the sub-query.  But since 'nextval' is a volatile function, we
should not push it.

Volatile functions give different results with each execution. We don't want
aggs to use result of a volatile function before it is necessary. We do it for
all aggs - DISTINCT and GROUP BY.

Also see commit 6327f25d.

1. The CurrentMemoryContext in CreateCheckPoint is long-live
memory context owned by the checkpointer process. The memory context
is reset only if the error occurs. So memory leak will lead to
huge memory leak in the OS.
2. The prepared transactions are not appended as an extension in
the checkpoint wal record, which introduces a bug. It occurs:
  1) T1 does some DML and is prepared.
  2) T2 runs a checkpoint.
  3) The seg0 crashes before the transaction T1 successfully runs `COMMIT PREPARE`, but
     all other segments have successfully committed.
  4) When running local recovery, seg0 doesn't know T1 is prepared
     and needs to be committed again.
This is different from the master branch. Master uses files to record
whether there exists any prepared transaction and what them are.
Reviewed-by: NNing Yu <nyu@pivotal.io>
Reviewed-by: NGang Xiong <gxiong@pivotal.io>

The shared oldestXmin (DistributedLogShared->oldestXmin) may be updated
concurrently. It should be set to a higher value, because a higher xmin
can belong to another distributed log segment, its older segments might
already be truncated.

For Example: txA and txB call DistributedLog_AdvanceOldestXmin concurrently.

```
txA and txB: both hold shared DistributedLogTruncateLock.

txA: set the DistributedLogShared->oldestXmin to XminA. TransactionIdToSegment(XminA) = 0009

txB: set the DistributedLogShared->oldestXmin to XminB. TransactionIdToSegment(XminB) = 0008

txA: truncate segment 0008, 0007...
```

After that, DistributedLogShared->oldestXmin == XminB, it is on removed
segment 0008. Subsequent GetSnapshotData() calls will be failed because SimpleLruReadPage will error out.
Co-authored-by: Ndh-cloud <60729713+dh-cloud@users.noreply.github.com>

As reported in issue #9790, 'CTAS with no data' statement doesn't handle WITH
clause, the options in WITH clause should be added in 'pg_attribute_encoding'.

Previously, planner cannot generate plan when a replicated
table union all a general locus scan. A typical case is:

  select a from t_replicate_table
  union all
  select * from generate_series(1, 10);

The root cause is in the function `set_append_path_locus`
it deduces the whole append path's locus to be segmentgeneral.
This is reasonable. However, in the function `cdbpath_create_motion_path`
it fails to handle two issues in the case:
  * segmentgeneral locus to segmentgeneral locus
  * general locus to segmentgeneral locus
And the both above locus change does not need motion in fact.

This commit fixes this by:
  1. add a check at the very begining of `cdbpath_create_motion_path`
     that if the subpath's locus is the same as target locus, just return
  2. add logic to handle general locus to segmentgeneral locus, just return

In GPDB6, the access method oid is 7013 whereas it's 3013 in GPDB5.
Until now, the bitmap indexes were not marked invalid as the query to
update the catalog relied on incorrect OID.  This commit removes the
hardcoded oid, and instead uses a catalog query.

Also, GPDB uses the GUC allow_system_table_mods to allow updates on
catalog tables. While disabling the indexes with bpchar_pattern_ops
indexes, the GUC was not set and the query used to fail. This commit
fixes it too.

Since upgraded target master database is copied to segments, reset the
index status to valid where required. The queries to ensure that all the
objects have been migrated from old segment to new segments excludes
invalid objects and will complain that index has not been migrated. The
index will be marked invalid during upgrade of the segment.

* Add more detail to NOWAIT behavior; standardize gdd note

* Standardize gdd wording around SELECT FOR UPDATE

* Remove NOWAIT example from lock_wait description

* Standardize gdd note in LOCK syntax

* Revert "Standardize gdd note in LOCK syntax"

This reverts commit 53c51bd2f9871b097a74e25378d9c0a2d86825f9.

* Revert "Standardize gdd wording around SELECT FOR UPDATE"

This reverts commit 0dbd3845bb7c2300d3edd5053452800770378477.

* More edits to NOWAIT wording

* Docs - add MADlib 1.17 to compatibility table

* Revert "Docs - add MADlib 1.17 to compatibility table"

This reverts commit d4470e5c1bba81cf06c4110e378760616233064c.

* Edit from Mel

* Update GDD note to exclude SELECT FOR UPDATE affect, and emphasize table-level lock

* docs - add info about querying the pg_stat_last_operation tbl

* edits requested by david

This bug is particularly evident with queries containing a large array
IN clause, e.g "a IN (1, 3, 5, ...)".

As a first step to improve optimization times for such queries, this
commit reduces unnecessary re-allocation of histogram buckets during the
merging of statistics of disjunctive predicates.

It improves the performance of the target query with 7000 elements in
the array comparison by around 50%.

  The configure values are not used at all, so remove the unused codes here.
Authored-by: NTingfang Bao <baotingfang@gmail.com>

Greenplum 6 does not support large objects. In greenplum 5, if there are
large objects, schema restore to 6 will fail during upgrade as large
object creation will fail. So disallow upgrading if the source database
has large objects

Previously, in function bring_to_singleQE,
it depends on the path->param_info field to determine if the path
can be taken into consideration since we cannot pass params across
motion node. But this is not enough, for example, an index path's
param_info field might be null, but its orderbyclauses refs some
outer params. This commit fixes the issue by adding more check
for indexpath.

See Github Issue: https://github.com/greenplum-db/gpdb/issues/9733
for details.

In past, when create table and truncate table are in the same
transaction, Greenplum will call heap_truncate_one_rel() to truncate
the relation. But for AO tables, it has different segmenting logic,
which leads to some of segment files cannot be truncated to zero.

Using ao_truncate_one_rel to replace heap_truncate_one_rel() and
handle the segmenting by ao_foreach_extent_file().
Reviewed-by: NAshwin Agrawal <aagrawal@pivotal.io>
Reviewed-by: NSoumyadeep Chakraborty <sochakraborty@pivotal.io>
(cherry picked from commit bb8d0305)

GPDB 6 introduced a mechanism to distribute table tables on columns
using a custom hash opclass, instead of using cdbhash. Before this
commit, ORCA would ignore the distribution opclass, but ensuring the
translator would only allow queries in which all tables were distributed
by either their default or default "legacy" opclasses.

However, in case of tables distributed by legacy or default opclasses,
but joined using a non-default opclass operator, ORCA would produce an
incorrect plan, giving wrong results.

This commit fixes that bug by introducing support for distributed tables
using non-default opfamilies/opclasses. But, even though the support is
implemented, it is not fully enabled at this time. The logic to fallback
to planner when the plan contains tables distributed with non-default
non-legacy opclasses remains. Our intention is to support it fully in
the future.

How does this work?
For hash joins, capture the opfamily of each hash joinable operator. Use
that to create hash distribution spec requests for either side of the
join.  Scan operators derive a distribution spec based on opfamily
(corresponding to the opclass) of each distribution column.  If there is
a mismatch between distribution spec requested/derived, add a Motion
Redistribute node using the distribution function from the requested
hash opfamily.

The commit consists of several sub-sections:
- Capture distr opfamilies in CMDRelation and related classes

  For each distribution column of the relation, track the opfamily of
  "opclass" used in the DISTRIBUTED BY clause. This information is then
  relayed to CTableDescriptor & CPhysicalScan.

  Also support this in other CMDRelation subclasses: CMDRelationCTAS
  (via CLogicalCTAS) & CMDRelationExternalGPDB.

- Capture hash opfamily of CMDScalarOp using gpdb::GetCompatibleHashOpFamily()
  This is need to determined distribution spec requests from joins.

- Track hash opfamilies of join predicates

  This commit extends the caching of join keys in Hash/Merge joins by
  also caching the corresponding hash opfamilies of the '=' operators
  used in those predicates.

- Track opfamily in CDistributionSpecHashed.

  This commit also constructs CDistributionSpecHashed with opfamily
  information that was previously cached in CScalarGroup in the case of
  HashJoins.
  It also includes the compatibility checks that reject distributions
  specs with mismatched opfamilies in order to produce Redistribute
  motions.

- Capture default distribution (hash) opfamily in CMDType
- Handle legacy opfamilies in CMDScalarOp & CMDType
- Handle opfamilies in HashExprList Expr->DXL translation

ORCA-side notes:
1. To ensure correctness, equivalent classes can only be determined over
   a specific opfamily. For example, the expression `a = b` implies a &
   b belong to an equiv classes only for the opfamily `=` belongs to.
   Otherwise expression `b |=| c` can be used to imply a & c belong to
   the same equiv class, which is incorrect, as the opfamily of `=` and
   `|=|` differ.
   For this commit, determine equiv classes only for default opfamilies.
   This will ensure correct behavior for majority of cases.
2. This commit does *not* implement similar features for merge joins.
   That is left for future work.
3. This commit introduces two traceflags:
   - EopttraceConsiderOpfamiliesForDistribution: If this is off,
     opfamilies is ignored and set to NULL. This mimics behavior before
     this PR. Ctest MDPs are run this way.
   - EopttraceUseLegacyOpfamilies: Set if ANY distribution col in the
     query uses a legacy opfamily/opclass. MDCache getters will then
     return legacy opfamilies instead of the default opfamilies for all
     queries.

What new information is captured from GPDB?
1. Opfamily of each distribution column in CMDRelation,
   CMDRelationCtasGPDB & CMDRelationExternalGPDB
2. Compatible hash opfamily of each CMDScalarOp using
   gpdb::GetCompatibleHashOpFamily()
3. Default distribution (hash) opfamily of every type.
   This maybe NULL for some types. Needed for certain operators (e.g
   HashAgg) that request distribution spec that cannot be inferred in
   any other way: cannot derive it, cannot get it from any scalar op
   etc. See GetDefaultDistributionOpfamilyForType()
4. Legacy opfamilies for types & scalar operators.
   Needed for supporting tables distributed by legacy opclasses.

Other GPDB side changes:

1. HashExprList no longer carries the type of the expression (it is
   inferred from the expr instead). However, it now carries the hash
   opfamily to use when deriving the distribution hash function. To
   maintain compatibility with older versions, the opfamily is used only
   if EopttraceConsiderOpfamiliesForDistribution is set, otherwise,
   default hash distribution function of the type of the expr is used.
2. Don't worry about left & right types in get_compatible_hash_opfamily()
3. Consider COERCION_PATH_RELABELTYPE as binary coercible for ORCA.
4. EopttraceUseLegacyOpfamilies is set if any table is distributed by a
   legacy opclass.

This reverts commit 3e45f064.

This is a backport of PR(https://github.com/greenplum-db/gpdb/pull/9726)
for 6X_STABLE. NOWAIT only affects how SELCT locks rows as they are
obtained from the table. They are used by the execution. So, the SELECT
statement with locking clause will wait for the table lock if it
can't hold the table lock.

cdb_tidy_message is gpdb specific function. It will truncate the
error message to just keep the first line and copy other lines to
error details.
For JDBC drivers, they follow the Postgres's error message and only
keep error message in JDBC getWarnings function. It makes JDBC
dirver cannot print the full error message of gpdb.
It's better to follow postgres error format.

(cherry picked from commit 0d0c33bf)

Add a missing resource so that the ORCA dev pipeline can be run for both
master and 6X.

The gpepxand tests were going OOM with ORCA in debug build, as the
segments require more memory. Previously, ORCA was not being run in
debug build so this was not an issue. We've bumped up the instance from
n1-standard-2 to n1-standard-4, which doubles our memory from 7.5GB to
15GB.

Previously, this test depended on a very specific amount of memory being
"eaten" or consumed before it went OOM. ORCA using gpdb allocators
vs the legacy allocation (which is used in debug builds for leak
detection) changes the output. However, we have no way to detect or
change the output file depending on whether we're in debug build or not.

Now, instead of consuming the same amount of memory each time in the
test, we consume a small amount and ensure we don't go OOM. Then we
consume a larger amount and ensure we do go OOM. This hardens the test
while keeping the intent.

During the behave tests, we change some of the system limits such as
memory and overcommit configurations. Previously this was changed while
the cluster was running, which caused the container to crash when
setting some of these parameters with ORCA in debug build. Now, we stop
the cluster, change the limits, and start the cluster.

This was causing an ORCA assertion to fail and fall back, as we asserted
that if a type is not binary coercible, then it had a cast function.

Although this code considered domain->base type as binary coercible, it
did not consider base type->domain as binary coercible. However,
coercion paths of COERCION_PATH_RELABELTYPE are binary coercible, so we
should mark them as such for ORCA.

These were exposed when running ICW with ORCA asserts enabled.

In DeriveJoinStats, EopLogicalFullOuterJoin is also a valid logical join
operator. In IDatum, we need to check that doubles are within some
epsilon as we're not passing in the full 64 bit IEEE value to ORCA.

With fixing the assertion, we would need to regenerate the mdp for
MinCardinalityNaryJoin However, there is no DDL/query for this test so
it is difficult to update. Since it also didn't seem to provide much
value, we're removing it.

With the ORCA source in the GPDB repo, there is no use for Conan or the
depends directory anymore. Also, the gpbackup conan file was stale and wasn't
being used/supported.

The main change here is that we completely get rid of the ORCA prod
pipeline, as there's no need to create a tag/publish artifacts anymore.

We also now build and test the orca unit tests during the compile step.

Additionally, I've refactored the orca-dev "slack command" pipeline to
use the canonical compile_gpdb.bash script and based the pipeline off
the existing PR pipeline. This simplifies the `test_orca_pipeline.yml`
file significantly and it now doesn't rely on custom scripts.

There are still quite a few files in the concourse directory that are
used by the `test_explain_pipeline.yml` and a couple of pipelines that
are external to this repo. Some of these aren't actively being used and
need to be cleaned up/removed, but I'll leave that for a later time.

Also, uses https for xerces-c download and checks hash to ensure correct
download.

Previously, we used a config file that was modified by cmake. Instead,
use configure to modify macros. Additionally use a compile definition in
cmake so we don't need a separate config file in gpos.

This also enables compile-time warnings in the src/backend/gporca files. C++ files
in the translator never had these warnings enabled, and so are not
enabled in src/backend/gpopt. A block of unused code is removed to get
pass the compile warnings.

This simplifies some of the cmake files further.

Cmake should only build targets for use with gporca_test. GNU make
should build orca within GPDB. Remove the install target to decrease the
chance for confusion.

Also, add makefile to test directory so make clean works.

ORCA doesn't need a specific version anymore.

A query plan will now look like:
```
                QUERY PLAN
------------------------------------------
 Result  (cost=0.00..0.00 rows=1 width=1)
 Optimizer: Pivotal Optimizer (GPORCA)
(2 rows)
```

Update regression tests affected by this change.

Additionally, use g++ for compiling mock unit tests since we're linking
c++ files.

ORCA previously was built into a shared library using cmake. Now, we
build ORCA into the postgres binary.

We no longer need to check for ORCA libraries or version, as ORCA now
exists in the same repo and the concept of a version is not needed.